Merging upstream version 1.9.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

30 files changed, 1192 insertions, 1064 deletions

diff --git a/ChangeLog b/ChangeLog
index 2aa81e5..895b2f4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,9 +1,25 @@
+2020-06-27  Antonio Diaz Diaz  <antonio@gnu.org>
+
+	* Version 1.9 released.
+	* zcmp.cc zdiff.cc: Read standard input only if requested.
+	* zdiff.cc (main): Pass options '-W' and '-y' to diff.
+	* zutils.cc (test_format): Detect bzip2 and lzip files better.
+	* ztest.cc (main): Continue testing if any input file is a terminal.
+	  If verbosity >= 1, print number of files that failed the test.
+	* zcat.cc zgrep.cc ztest.cc (main): Check return value of close( infd ).
+	* zutils.cc (good_status): Ignore trailing data remaining in feeder.
+	* zupdate.cc (zupdate_file): Support new and old lzip option '-o'.
+	  Keep combined extensions: tgz, tbz, tbz2, txz --> tlz.
+	  Quote file names in zcmp_command to allow file names with spaces.
+	* *.cc (main): Set a valid invocation_name even if argc == 0.
+	* zutils.texi: Improve descriptions of zcat, zcmp, and zdiff.
+
 2019-01-01  Antonio Diaz Diaz  <antonio@gnu.org>
 
 	* Version 1.8 released.
-	* zcat.cc: Fixed a buffer overflow on outbuf when '-v' is used.
+	* zcat.cc: Fix a buffer overflow on outbuf when '-v' is used.
 	* zcat.cc (cat): A canary byte has been added to outbuf.
-	* Added new option '-R, --dereference-recursive'.
+	* New option '-R, --dereference-recursive'.
 	* Option '-r, --recursive' now skips symlinks.
 	* If no files and recursive, examine current working directory.
 	* recursive.cc (test_full_name): Detect directory loops.
@@ -11,21 +27,21 @@
 	* recursive.cc: Remove extra trailing slashes from directory args.
 	* zcatgrep.cc (open_instream): Show correct errno.
 	* zutils.cc (good_status): Wait for killed child.
-	* Test and document continuation or exit of zcat, zgrep, ztest
+	* Test and document continuation or exit of zcat, zgrep, ztest,
 	  and zupdate in case of error.
 	* configure: Accept appending to CXXFLAGS, 'CXXFLAGS+=OPTIONS'.
 
 2018-02-13  Antonio Diaz Diaz  <antonio@gnu.org>
 
 	* Version 1.7 released.
-	* zgrep.cc (main): Pass '--color' option to grep.
-	* check.sh: Added new tests for zgrep.
+	* zgrep.cc (main): Pass option '--color' to grep.
+	* check.sh: Add new tests for zgrep.
 
 2017-04-05  Antonio Diaz Diaz  <antonio@gnu.org>
 
 	* Version 1.6 released.
 	* zcmp.cc: Accept 'B' suffix in '--ignore-initial=1kB:1234B'.
-	* zutils.cc (feed_data): Show input filename in error messages.
+	* zutils.cc (feed_data): Show input file name in error messages.
 
 2016-05-15  Antonio Diaz Diaz  <antonio@gnu.org>
 
@@ -41,124 +57,123 @@
 
 	* Version 1.4 released.
 	* Option '--format' has been renamed to '-O, --force-format'.
-	* Added new option '-M, --format=<list>' to all utilities.
+	* Add new option '-M, --format=<list>' to all utilities.
 	* zgrep.cc (main): Pass '-e' to grep if pattern begins with '-'.
-	* Makefile.in: Added new targets 'install*-compress'.
+	* Makefile.in: New targets 'install*-compress'.
 
 2014-08-30  Antonio Diaz Diaz  <antonio@gnu.org>
 
 	* Version 1.3 released.
-	* check.sh: Fixed two values of expected exit status.
-	* zutils.texi: Documented that '--format' does not verify format.
-	* Added two missing #includes.
-	* License changed to GPL version 2 or later.
+	* check.sh: Fix two values of expected exit status.
+	* zutils.texi: Document that '--format' does not verify format.
+	* Add two missing #includes.
+	* Change license to GPL version 2 or later.
 
 2014-02-01  Antonio Diaz Diaz  <antonio@gnu.org>
 
 	* Version 1.2 released.
-	* Added new utility; zupdate.
-	* Removed zutils executable. Utils are now independent executables.
-	* zgrep.cc: Fixed the exit status returned on error.
-	* zutils.texinfo: Renamed to zutils.texi.
+	* New utility; zupdate.
+	* Remove zutils executable. Utils are now independent executables.
+	* zgrep.cc: Fix the exit status returned on error.
+	* zutils.texinfo: Rename to zutils.texi.
 
 2013-08-02  Antonio Diaz Diaz  <antonio@gnu.org>
 
 	* Version 1.1 released.
-	* Added options '--bz2', '--gz', '--lz' and '--xz' to all utilities.
-	* Added runtime configuration file 'zutilsrc'.
+	* Add options '--bz2', '--gz', '--lz', and '--xz' to all utilities.
+	* Add runtime configuration file 'zutilsrc'.
 	* New function 'good_status' checks exit status of all children.
-	* Fixed all uses of decompressed/uncompressed in the documentation.
+	* Fix all uses of decompressed/uncompressed in the documentation.
 
 2013-05-31  Antonio Diaz Diaz  <antonio@gnu.org>
 
 	* Version 1.0 released.
-	* Added new option '--format' to all utilities.
+	* Add new option '--format' to all utilities.
 	* main.cc (main): Make 'grep_show_name' tri-state so that file
 	  name is no prefixed to output by default when searching one
 	  file and '--recursive' has not been selected.
-	* Zgrep: Fixed output of option '-L' (it behaved like '-l').
-	* zcmp.cc: Fixed deadlock when '-n' option is used.
-	* zdiff.cc (set_data_feeder): Call compressor with option "-q"
+	* Zgrep: Fix output of option '-L' (it behaved like '-l').
+	* zcmp.cc: Fix deadlock when option '-n' is used.
+	* zdiff.cc (set_data_feeder): Call compressor with option '-q'
 	  only if verbosity < 0.
 	* zutils.cc (set_data_feeder): Likewise.
-	* Changed quote characters in messages as advised by GNU Standards.
+	* Change quote characters in messages as advised by GNU Standards.
 	* configure: Options now accept a separate argument.
-	* configure: 'datadir' renamed to 'datarootdir'.
-	* Makefile.in: Added new target 'install-bin'.
+	  Rename 'datadir' to 'datarootdir'. Ignore environment variables.
+	* Makefile.in: New target 'install-bin'.
 	* Use 'setmode' instead of '_setmode' on Windows and OS/2.
-	* zcat.cc (Line_number): Fixed a portability issue with Solaris 9.
+	* zcat.cc (Line_number): Fix a portability issue with Solaris 9.
 	* INSTALL: Document installing zutils along with GNU gzip.
 
 2011-01-11  Antonio Diaz Diaz  <ant_diaz@teleline.es>
 
 	* Version 0.9 released.
-	* configure: Added new options 'DIFF' and 'GREP'.
-	* zcmp.cc: Fixed deadlock when files differ.
-	* zgrep.cc: Fixed deadlock when binary file matches.
+	* configure: New options 'DIFF' and 'GREP'.
+	* zcmp.cc: Fix deadlock when files differ.
+	* zgrep.cc: Fix deadlock when binary file matches.
 
 2010-11-15  Antonio Diaz Diaz  <ant_diaz@teleline.es>
 
 	* Version 0.8 released.
-	* main.cc: Added new options '--zcat', '--zgrep' and '--ztest'.
+	* main.cc: New options '--zcat', '--zgrep', and '--ztest'.
 	* zcat.cc: New file implementing zcat+cat functionality in C++.
 	* zcmp.cc: New file implementing zcmp+cmp functionality in C++.
 	* doc/zcmp.1: New file.
-	* zcmp.in: Removed.
+	* Remove files zcmp.in, zdiff.in.
 	* zdiff.cc: New file implementing zdiff functionality in C++.
-	* zdiff.in: Removed.
 	* zgrep.cc: New file implementing zgrep functionality in C++.
 	* All mentions to zegrep and zfgrep have been removed from the
 	  documentation because egrep and fgrep are deprecated.
 	* ztest.cc: New file implementing ztest functionality in C++.
-	* Makefile.in: Added quotes to directory names.
+	* Makefile.in: Add quotes to directory names.
 	* check.sh: Use 'test.txt' instead of 'COPYING' for testing.
-	* Removed environment safeguards from configure as requested by
+	* Remove environment safeguards from configure as requested by
 	  Richard Stallman. Now environment variables affect configure.
 
 2009-10-21  Antonio Diaz Diaz  <ant_diaz@teleline.es>
 
 	* Version 0.7 released.
-	* Added new utility; ztest.
-	* zcat.in: Added new option '--recursive'.
+	* New utility; ztest.
+	* zcat.in: New option '-r, --recursive'.
 
 2009-10-05  Antonio Diaz Diaz  <ant_diaz@teleline.es>
 
 	* Version 0.6 released.
-	* zcat.in, zgrep.in: Removed again default compressor. Format of
+	* zcat.in, zgrep.in: Remove again default compressor. Format of
 	  data read from stdin is now automatically detected.
-	* Makefile.in: Added '--name' option to help2man invocation.
+	* Makefile.in: Add option '--name' to help2man invocation.
 
 2009-10-01  Antonio Diaz Diaz  <ant_diaz@teleline.es>
 
 	* Version 0.5 released.
 	* zcat.in, zgrep.in: Read again data from stdin.
-	* Added again default compressor for stdin only.
+	* Add again default compressor for stdin only.
 
 2009-09-17  Antonio Diaz Diaz  <ant_diaz@teleline.es>
 
 	* Version 0.4 released.
-	* Added two new utilities; zegrep and zfgrep.
-	* Added zutils executable which recognizes file formats.
+	* Add two new utilities; zegrep and zfgrep.
+	* Add zutils executable which recognizes file formats.
 
 2009-08-28  Antonio Diaz Diaz  <ant_diaz@teleline.es>
 
 	* Version 0.3 released.
-	* Removed default compressor.
+	* Remove default compressor.
 	* zcat.in, zgrep.in: Don't read data from stdin.
-	* Updated home page and mailing list addresses.
+	* Update home page and mailing list addresses.
 
 2009-08-13  Antonio Diaz Diaz  <ant_diaz@teleline.es>
 
 	* Version 0.2 released.
-	* Added support for xz.
+	* Add support for xz.
 
 2009-08-07  Antonio Diaz Diaz  <ant_diaz@teleline.es>
 
 	* Version 0.1 released.
 
 
-Copyright (C) 2009-2019 Antonio Diaz Diaz.
+Copyright (C) 2009-2020 Antonio Diaz Diaz.
 
 This file is a collection of facts, and thus it is not copyrightable,
-but just in case, you have unlimited permission to copy, distribute and
+but just in case, you have unlimited permission to copy, distribute, and
 modify it.
diff --git a/INSTALL b/INSTALL
index 42cb5df..a56c227 100644
--- a/INSTALL
+++ b/INSTALL
@@ -1,7 +1,7 @@
 Requirements
 ------------
-You will need a C++ compiler.
-I use gcc 5.3.0 and 4.1.2, but the code should compile with any standards
+You will need a C++11 compiler. (gcc 3.3.6 or newer is recommended).
+I use gcc 6.1.0 and 4.1.2, but the code should compile with any standards
 compliant compiler.
 Gcc is available at http://gcc.gnu.org.
 
@@ -44,21 +44,21 @@ the main archive.
    documentation.
 
    Or type 'make install-compress', which additionally compresses the
-   info manual and the man pages after installation. (Installing
-   compressed docs may become the default in the future).
+   info manual and the man pages after installation.
+   (Installing compressed docs may become the default in the future).
 
-   You can install only the programs, the info manual or the man pages by
-   typing 'make install-bin', 'make install-info' or 'make install-man'
+   You can install only the programs, the info manual, or the man pages by
+   typing 'make install-bin', 'make install-info', or 'make install-man'
    respectively.
 
 
 Another way
 -----------
 You can also compile zutils into a separate directory.
-To do this, you must use a version of 'make' that supports the 'VPATH'
-variable, such as GNU 'make'. 'cd' to the directory where you want the
+To do this, you must use a version of 'make' that supports the variable
+'VPATH', such as GNU 'make'. 'cd' to the directory where you want the
 object files and executables to go and run the 'configure' script.
-'configure' automatically checks for the source code in '.', in '..' and
+'configure' automatically checks for the source code in '.', in '..', and
 in the directory that 'configure' is in.
 
 'configure' recognizes the option '--srcdir=DIR' to control where to
@@ -69,7 +69,7 @@ After running 'configure', you can run 'make' and 'make install' as
 explained above.
 
 
-Copyright (C) 2009-2019 Antonio Diaz Diaz.
+Copyright (C) 2009-2020 Antonio Diaz Diaz.
 
 This file is free documentation: you have unlimited permission to copy,
-distribute and modify it.
+distribute, and modify it.
diff --git a/Makefile.in b/Makefile.in
index 7ca371a..55a974e 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -135,8 +135,8 @@ install-bin : all
 	$(INSTALL_PROGRAM) ./ztest "$(DESTDIR)$(bindir)/ztest"
 	$(INSTALL_PROGRAM) ./zupdate "$(DESTDIR)$(bindir)/zupdate"
 	if [ ! -e "$(DESTDIR)$(sysconfdir)/$(pkgname)rc" ] ; then \
-		if [ ! -d "$(DESTDIR)$(sysconfdir)" ] ; then $(INSTALL_DIR) "$(DESTDIR)$(sysconfdir)" ; fi ; \
-		$(INSTALL_DATA) $(VPATH)/$(pkgname)rc "$(DESTDIR)$(sysconfdir)/$(pkgname)rc" ; \
+	  if [ ! -d "$(DESTDIR)$(sysconfdir)" ] ; then $(INSTALL_DIR) "$(DESTDIR)$(sysconfdir)" ; fi ; \
+	  $(INSTALL_DATA) $(VPATH)/$(pkgname)rc "$(DESTDIR)$(sysconfdir)/$(pkgname)rc" ; \
 	fi
 
 install-bin-strip : all
@@ -147,7 +147,7 @@ install-info :
 	-rm -f "$(DESTDIR)$(infodir)/$(pkgname).info"*
 	$(INSTALL_DATA) $(VPATH)/doc/$(pkgname).info "$(DESTDIR)$(infodir)/$(pkgname).info"
 	-if $(CAN_RUN_INSTALLINFO) ; then \
-		install-info --info-dir="$(DESTDIR)$(infodir)" "$(DESTDIR)$(infodir)/$(pkgname).info" ; \
+	  install-info --info-dir="$(DESTDIR)$(infodir)" "$(DESTDIR)$(infodir)/$(pkgname).info" ; \
 	fi
 
 install-info-compress : install-info
@@ -191,7 +191,7 @@ uninstall-bin :
 
 uninstall-info :
 	-if $(CAN_RUN_INSTALLINFO) ; then \
-		install-info --info-dir="$(DESTDIR)$(infodir)" --remove "$(DESTDIR)$(infodir)/$(pkgname).info" ; \
+	  install-info --info-dir="$(DESTDIR)$(infodir)" --remove "$(DESTDIR)$(infodir)/$(pkgname).info" ; \
 	fi
 	-rm -f "$(DESTDIR)$(infodir)/$(pkgname).info"*
 
diff --git a/NEWS b/NEWS
index af8629f..5ea6cf0 100644
--- a/NEWS
+++ b/NEWS
@@ -1,38 +1,36 @@
-Changes in version 1.8:
+Changes in version 1.9:
 
-A buffer overflow has been fixed in zcat which happened sometimes when
-the '-v, --show-nonprinting' option was used (or indirectly enabled).
-A canary byte has been added to the output buffer to prevent the buffer
-overflow from happening again.
+zcmp anf zdiff now meet the POSIX requirement for cmp and diff that the
+standard input shall be used only if the file1 or file2 operand refers to
+standard input.
 
-The option '-R, --dereference-recursive', which recursively follows
-symbolic links, has been added to zcat, zgrep, ztest and zupdate.
+zdiff now passes the options '-W' and '-y' to diff. (But it only works if
+the diff program used supports them).
 
-The option '-r, --recursive' now skips symlinks that are encountered
-recursively.
+Bzip2 and lzip files are now detected better.
+('echo LZIP | zcat' and 'echo BZh5 | zcat' no longer return an error).
 
-If no files are given to zcat, zgrep, ztest and zupdate, a recursive
-search will now examine the current working directory.
+ztest now continues checking the rest of the files if any input file is a
+terminal.
 
-Recursive directory loops are now detected.
+'ztest -v' now prints the number of files that failed the test (like lzip).
 
-zcat and zgrep now ignore directories given in the command line if
-'--recursive' is not specified, instead of reporting an error.
+zcat, zgrep, and ztest now check for errors when closing the input file in
+addition to checking when closing the input from the decompressor.
 
-Extra trailing slashes are now removed from directories given in the
-command line before recursing into them.
+Trailing data remaining in the data feeder to the decompressor are now
+correctly ignored.
 
-zcat and zgrep now show the right error when they can't open an input
-file instead of showing "No such file or directory".
+zupdate has been modified to support the new behavior of lzip 1.22's option
+'-o' while retaining:
+perfect backwards compatibility with older versions of lzip down to 1.20,
+good backwards compatibility with older versions of lzip down to 1.11,
+acceptable backwards compatibility with older versions of lzip down to 1.4.
 
-Killed decompressors are now waited for, preventing failure caused by
-too many open pipes.
+zupdate now keeps combined extensions: tgz, tbz, tbz2, txz --> tlz.
+This is useful when recompressing Slackware packages, for example.
 
-Test and document that if a file fails to decompress, zcat, zgrep and
-ztest continue processing the rest of the files.
+zupdate now puts single quotes around file names when calling zcmp to allow
+file names with spaces. (But putting spaces in file names is a bad idea).
 
-Test and document that if an error happens while recompressing a file,
-zupdate exits immediately without recompressing the rest of the files.
-
-The configure script now accepts appending options to CXXFLAGS using the
-syntax 'CXXFLAGS+=OPTIONS'.
+The descriptions of zcat, zcmp, and zdiff have been improved.
diff --git a/README b/README
index 7ca6729..86ec037 100644
--- a/README
+++ b/README
@@ -1,46 +1,46 @@
 Description
 
 Zutils is a collection of utilities able to process any combination of
-compressed and uncompressed files transparently. If any given file,
-including standard input, is compressed, its decompressed content is
-used. Compressed files are decompressed on the fly; no temporary files
-are created.
+compressed and uncompressed files transparently. If any file given,
+including standard input, is compressed, its decompressed content is used.
+Compressed files are decompressed on the fly; no temporary files are
+created.
 
 These utilities are not wrapper scripts but safer and more efficient C++
-programs. In particular the '--recursive' option is very efficient in
+programs. In particular the option '--recursive' is very efficient in
 those utilities supporting it.
 
-The utilities provided are zcat, zcmp, zdiff, zgrep, ztest and zupdate.
-The formats supported are bzip2, gzip, lzip and xz.
-Zutils uses external compressors. The compressor to be used for each
-format is configurable at runtime.
+The utilities provided are zcat, zcmp, zdiff, zgrep, ztest, and zupdate.
+The formats supported are bzip2, gzip, lzip, and xz.
+Zutils uses external compressors. The compressor to be used for each format
+is configurable at runtime.
 
-zcat, zcmp, zdiff, and zgrep are improved replacements for the shell
-scripts provided by GNU gzip. ztest is unique to zutils. zupdate is
-similar to gzip's znew.
+zcat, zcmp, zdiff, and zgrep are improved replacements for the shell scripts
+provided by GNU gzip. ztest is unique to zutils. zupdate is similar to
+gzip's znew.
 
-NOTE: Bzip2 and lzip provide well-defined values of exit status, which
-makes them safe to use with zutils. Gzip and xz may return ambiguous
-warning values, making them less reliable back ends for zutils.
+NOTE: Bzip2 and lzip provide well-defined values of exit status, which makes
+them safe to use with zutils. Gzip and xz may return ambiguous warning
+values, making them less reliable back ends for zutils.
 
-FORMAT NOTE 1: The '--format' option allows the processing of a subset
+FORMAT NOTE 1: The option '--format' allows the processing of a subset
 of formats in recursive mode and when trying compressed file names:
 'zgrep foo -r --format=bz2,lz somedir somefile.tar'.
 
-FORMAT NOTE 2: If the '--force-format' option is given, the files are
+FORMAT NOTE 2: If the option '--force-format' is given, the files are
 passed to the corresponding decompressor without verifying their format,
 allowing for example the processing of compress'd (.Z) files with gzip:
 'zcmp --force-format=gz file.Z file.lz'.
 
-LANGUAGE NOTE: Uncompressed = not compressed = plain data; it may never
-have been compressed. Decompressed is used to refer to data which have
-undergone the process of decompression.
+LANGUAGE NOTE: Uncompressed = not compressed = plain data; it may never have
+been compressed. Decompressed is used to refer to data which have undergone
+the process of decompression.
 
 
-Copyright (C) 2009-2019 Antonio Diaz Diaz.
+Copyright (C) 2009-2020 Antonio Diaz Diaz.
 
 This file is free documentation: you have unlimited permission to copy,
-distribute and modify it.
+distribute, and modify it.
 
 The file Makefile.in is a data file used by configure to produce the
 Makefile. It has the same copyright owner and permissions that configure
diff --git a/arg_parser.cc b/arg_parser.cc
index ea32fde..b843c09 100644
--- a/arg_parser.cc
+++ b/arg_parser.cc
@@ -1,20 +1,20 @@
-/*  Arg_parser - POSIX/GNU command line argument parser. (C++ version)
-    Copyright (C) 2006-2019 Antonio Diaz Diaz.
+/* Arg_parser - POSIX/GNU command line argument parser. (C++ version)
+   Copyright (C) 2006-2020 Antonio Diaz Diaz.
 
-    This library is free software. Redistribution and use in source and
-    binary forms, with or without modification, are permitted provided
-    that the following conditions are met:
+   This library is free software. Redistribution and use in source and
+   binary forms, with or without modification, are permitted provided
+   that the following conditions are met:
 
-    1. Redistributions of source code must retain the above copyright
-    notice, this list of conditions and the following disclaimer.
+   1. Redistributions of source code must retain the above copyright
+   notice, this list of conditions, and the following disclaimer.
 
-    2. Redistributions in binary form must reproduce the above copyright
-    notice, this list of conditions and the following disclaimer in the
-    documentation and/or other materials provided with the distribution.
+   2. Redistributions in binary form must reproduce the above copyright
+   notice, this list of conditions, and the following disclaimer in the
+   documentation and/or other materials provided with the distribution.
 
-    This library is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+   This library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 */
 
 #include <cstring>
@@ -167,7 +167,7 @@ Arg_parser::Arg_parser( const int argc, const char * const argv[],
       else non_options.push_back( argv[argind++] );
       }
     }
-  if( error_.size() ) data.clear();
+  if( !error_.empty() ) data.clear();
   else
     {
     for( unsigned i = 0; i < non_options.size(); ++i )
@@ -190,7 +190,7 @@ Arg_parser::Arg_parser( const char * const opt, const char * const arg,
       { if( opt[2] ) parse_long_option( opt, arg, options, argind ); }
     else
       parse_short_option( opt, arg, options, argind );
-    if( error_.size() ) data.clear();
+    if( !error_.empty() ) data.clear();
     }
   else data.push_back( Record( opt ) );
   }
diff --git a/arg_parser.h b/arg_parser.h
index ceb9933..d9a4af0 100644
--- a/arg_parser.h
+++ b/arg_parser.h
@@ -1,43 +1,43 @@
-/*  Arg_parser - POSIX/GNU command line argument parser. (C++ version)
-    Copyright (C) 2006-2019 Antonio Diaz Diaz.
+/* Arg_parser - POSIX/GNU command line argument parser. (C++ version)
+   Copyright (C) 2006-2020 Antonio Diaz Diaz.
 
-    This library is free software. Redistribution and use in source and
-    binary forms, with or without modification, are permitted provided
-    that the following conditions are met:
+   This library is free software. Redistribution and use in source and
+   binary forms, with or without modification, are permitted provided
+   that the following conditions are met:
 
-    1. Redistributions of source code must retain the above copyright
-    notice, this list of conditions and the following disclaimer.
+   1. Redistributions of source code must retain the above copyright
+   notice, this list of conditions, and the following disclaimer.
 
-    2. Redistributions in binary form must reproduce the above copyright
-    notice, this list of conditions and the following disclaimer in the
-    documentation and/or other materials provided with the distribution.
+   2. Redistributions in binary form must reproduce the above copyright
+   notice, this list of conditions, and the following disclaimer in the
+   documentation and/or other materials provided with the distribution.
 
-    This library is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+   This library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 */
 
-/*  Arg_parser reads the arguments in 'argv' and creates a number of
-    option codes, option arguments and non-option arguments.
+/* Arg_parser reads the arguments in 'argv' and creates a number of
+   option codes, option arguments, and non-option arguments.
 
-    In case of error, 'error' returns a non-empty error message.
+   In case of error, 'error' returns a non-empty error message.
 
-    'options' is an array of 'struct Option' terminated by an element
-    containing a code which is zero. A null name means a short-only
-    option. A code value outside the unsigned char range means a
-    long-only option.
+   'options' is an array of 'struct Option' terminated by an element
+   containing a code which is zero. A null name means a short-only
+   option. A code value outside the unsigned char range means a
+   long-only option.
 
-    Arg_parser normally makes it appear as if all the option arguments
-    were specified before all the non-option arguments for the purposes
-    of parsing, even if the user of your program intermixed option and
-    non-option arguments. If you want the arguments in the exact order
-    the user typed them, call 'Arg_parser' with 'in_order' = true.
+   Arg_parser normally makes it appear as if all the option arguments
+   were specified before all the non-option arguments for the purposes
+   of parsing, even if the user of your program intermixed option and
+   non-option arguments. If you want the arguments in the exact order
+   the user typed them, call 'Arg_parser' with 'in_order' = true.
 
-    The argument '--' terminates all options; any following arguments are
-    treated as non-option arguments, even if they begin with a hyphen.
+   The argument '--' terminates all options; any following arguments are
+   treated as non-option arguments, even if they begin with a hyphen.
 
-    The syntax for optional option arguments is '-<short_option><argument>'
-    (without whitespace), or '--<long_option>=<argument>'.
+   The syntax for optional option arguments is '-<short_option><argument>'
+   (without whitespace), or '--<long_option>=<argument>'.
 */
 
 class Arg_parser
@@ -61,6 +61,7 @@ private:
     explicit Record( const char * const arg ) : code( 0 ), argument( arg ) {}
     };
 
+  const std::string empty_arg;
   std::string error_;
   std::vector< Record > data;
 
@@ -73,17 +74,17 @@ public:
   Arg_parser( const int argc, const char * const argv[],
               const Option options[], const bool in_order = false );
 
-      // Restricted constructor. Parses a single token and argument (if any)
+  // Restricted constructor. Parses a single token and argument (if any).
   Arg_parser( const char * const opt, const char * const arg,
               const Option options[] );
 
   const std::string & error() const { return error_; }
 
-      // The number of arguments parsed (may be different from argc)
+  // The number of arguments parsed. May be different from argc.
   int arguments() const { return data.size(); }
 
-      // If code( i ) is 0, argument( i ) is a non-option.
-      // Else argument( i ) is the option's argument (or empty).
+  /* If code( i ) is 0, argument( i ) is a non-option.
+     Else argument( i ) is the option's argument (or empty). */
   int code( const int i ) const
     {
     if( i >= 0 && i < arguments() ) return data[i].code;
@@ -93,6 +94,6 @@ public:
   const std::string & argument( const int i ) const
     {
     if( i >= 0 && i < arguments() ) return data[i].argument;
-    else return error_;
+    else return empty_arg;
     }
   };
diff --git a/configure b/configure
index d8fd626..dfef6bc 100755
--- a/configure
+++ b/configure
@@ -1,12 +1,12 @@
 #! /bin/sh
 # configure script for Zutils - Utilities dealing with compressed files
-# Copyright (C) 2009-2019 Antonio Diaz Diaz.
+# Copyright (C) 2009-2020 Antonio Diaz Diaz.
 #
 # This configure script is free software: you have unlimited permission
-# to copy, distribute and modify it.
+# to copy, distribute, and modify it.
 
 pkgname=zutils
-pkgversion=1.8
+pkgversion=1.9
 srctrigger=doc/${pkgname}.texi
 
 # clear some things potentially inherited from environment.
@@ -28,11 +28,7 @@ DIFF=diff
 GREP=grep
 
 # checking whether we are using GNU C++.
-/bin/sh -c "${CXX} --version" > /dev/null 2>&1 ||
-	{
-	CXX=c++
-	CXXFLAGS=-O2
-	}
+/bin/sh -c "${CXX} --version" > /dev/null 2>&1 || { CXX=c++ ; CXXFLAGS=-O2 ; }
 
 # Loop over all args
 args=
@@ -44,11 +40,12 @@ while [ $# != 0 ] ; do
 	shift
 
 	# Add the argument quoted to args
-	args="${args} \"${option}\""
+	if [ -z "${args}" ] ; then args="\"${option}\""
+	else args="${args} \"${option}\"" ; fi
 
 	# Split out the argument for options that take them
 	case ${option} in
-	*=*) optarg=`echo ${option} | sed -e 's,^[^=]*=,,;s,/$,,'` ;;
+	*=*) optarg=`echo "${option}" | sed -e 's,^[^=]*=,,;s,/$,,'` ;;
 	esac
 
 	# Process the options
@@ -134,7 +131,7 @@ if [ -z "${srcdir}" ] ; then
 	if [ ! -r "${srcdir}/${srctrigger}" ] ; then srcdir=.. ; fi
 	if [ ! -r "${srcdir}/${srctrigger}" ] ; then
 		## the sed command below emulates the dirname command
-		srcdir=`echo $0 | sed -e 's,[^/]*$,,;s,/$,,;s,^$,.,'`
+		srcdir=`echo "$0" | sed -e 's,[^/]*$,,;s,/$,,;s,^$,.,'`
 	fi
 fi
 
@@ -157,7 +154,7 @@ if [ -z "${no_create}" ] ; then
 # Run this file to recreate the current configuration.
 #
 # This script is free software: you have unlimited permission
-# to copy, distribute and modify it.
+# to copy, distribute, and modify it.
 
 exec /bin/sh $0 ${args} --no-create
 EOF
@@ -182,11 +179,11 @@ echo "GREP = ${GREP}"
 rm -f Makefile
 cat > Makefile << EOF
 # Makefile for Zutils - Utilities dealing with compressed files
-# Copyright (C) 2009-2019 Antonio Diaz Diaz.
+# Copyright (C) 2009-2020 Antonio Diaz Diaz.
 # This file was generated automatically by configure. Don't edit.
 #
 # This Makefile is free software: you have unlimited permission
-# to copy, distribute and modify it.
+# to copy, distribute, and modify it.
 
 pkgname = ${pkgname}
 pkgversion = ${pkgversion}
diff --git a/doc/zcat.1 b/doc/zcat.1
index 443f813..29966ad 100644
--- a/doc/zcat.1
+++ b/doc/zcat.1
@@ -1,27 +1,29 @@
 .\" DO NOT MODIFY THIS FILE!  It was generated by help2man 1.46.1.
-.TH ZCAT "1" "January 2019" "zcat (zutils) 1.8" "User Commands"
+.TH ZCAT "1" "June 2020" "zcat (zutils) 1.9" "User Commands"
 .SH NAME
 zcat \- decompress and concatenate files to standard output
 .SH SYNOPSIS
 .B zcat
 [\fI\,options\/\fR] [\fI\,files\/\fR]
 .SH DESCRIPTION
-Zcat copies each given file to standard output. If any given file is
-compressed, its decompressed content is used. If a given file does not
-exist, and its name does not end with one of the known extensions, zcat
-tries the compressed file names corresponding to the formats supported.
+zcat copies each file argument to standard output in sequence. If any
+file given is compressed, its decompressed content is copied. If a file
+given does not exist, and its name does not end with one of the known
+extensions, zcat tries the compressed file names corresponding to the
+formats supported. If a file fails to decompress, zcat continues copying the
+rest of the files.
 .PP
 If a file is specified as '\-', data are read from standard input,
 decompressed if needed, and sent to standard output. Data read from
 standard input must be of the same type; all uncompressed or all in the
-same compression format.
+same compressed format.
 .PP
 If no files are specified, recursive searches examine the current
 working directory, and nonrecursive searches read standard input.
 .PP
-The formats supported are bzip2, gzip, lzip and xz.
+The formats supported are bzip2, gzip, lzip, and xz.
 .PP
-Exit status is 0 if no errors occurred, non\-zero otherwise.
+Exit status is 0 if no errors occurred, 1 otherwise.
 .SH OPTIONS
 .TP
 \fB\-h\fR, \fB\-\-help\fR
@@ -52,7 +54,7 @@ number all output lines
 don't read runtime configuration file
 .TP
 \fB\-O\fR, \fB\-\-force\-format=\fR<fmt>
-force given format (bz2, gz, lz, xz)
+force the format given (bz2, gz, lz, xz)
 .TP
 \fB\-q\fR, \fB\-\-quiet\fR
 suppress all messages
@@ -94,7 +96,7 @@ Report bugs to zutils\-bug@nongnu.org
 .br
 Zutils home page: http://www.nongnu.org/zutils/zutils.html
 .SH COPYRIGHT
-Copyright \(co 2019 Antonio Diaz Diaz.
+Copyright \(co 2020 Antonio Diaz Diaz.
 License GPLv2+: GNU GPL version 2 or later <http://gnu.org/licenses/gpl.html>
 .br
 This is free software: you are free to change and redistribute it.
diff --git a/doc/zcmp.1 b/doc/zcmp.1
index e56b46f..b11d79b 100644
--- a/doc/zcmp.1
+++ b/doc/zcmp.1
@@ -1,31 +1,29 @@
 .\" DO NOT MODIFY THIS FILE!  It was generated by help2man 1.46.1.
-.TH ZCMP "1" "January 2019" "zcmp (zutils) 1.8" "User Commands"
+.TH ZCMP "1" "June 2020" "zcmp (zutils) 1.9" "User Commands"
 .SH NAME
 zcmp \- decompress and compare two files byte by byte
 .SH SYNOPSIS
 .B zcmp
 [\fI\,options\/\fR] \fI\,file1 \/\fR[\fI\,file2\/\fR]
 .SH DESCRIPTION
-Zcmp compares two files ('\-' means standard input), and if they differ,
-tells the first byte and line number where they differ. Bytes and lines
-are numbered starting with 1. If any given file is compressed, its
-decompressed content is used. Compressed files are decompressed on the
-fly; no temporary files are created.
+zcmp compares two files and, if they differ, writes to standard output the
+first byte and line number where they differ. Bytes and lines are numbered
+starting with 1. A hyphen '\-' used as a file argument means standard input.
+If any file given is compressed, its decompressed content is used. Compressed
+files are decompressed on the fly; no temporary files are created.
 .PP
-The formats supported are bzip2, gzip, lzip and xz.
+The formats supported are bzip2, gzip, lzip, and xz.
 .PP
-Zcmp compares file1 to file2. If file2 is omitted zcmp tries the
+zcmp compares file1 to file2. The standard input is used only if file1 or
+file2 refers to standard input. If file2 is omitted zcmp tries the
 following:
 .IP
-1. If file1 is compressed, compares its decompressed contents with
+\- If file1 is compressed, compares its decompressed contents with
 the corresponding uncompressed file (the name of file1 with the
 extension removed).
 .IP
-2. If file1 is uncompressed, compares it with the decompressed
+\- If file1 is uncompressed, compares it with the decompressed
 contents of file1.[lz|bz2|gz|xz] (the first one that is found).
-.IP
-3. If no suitable file is found, compares file1 with data read from
-standard input.
 .PP
 Exit status is 0 if inputs are identical, 1 if different, 2 if trouble.
 .SH OPTIONS
@@ -55,7 +53,7 @@ compare at most <n> bytes
 don't read runtime configuration file
 .TP
 \fB\-O\fR, \fB\-\-force\-format\fR=\fI\,[\/\fR<f1>][,<f2>]
-force given formats (bz2, gz, lz, xz)
+force the formats given (bz2, gz, lz, xz)
 .TP
 \fB\-q\fR, \fB\-\-quiet\fR
 suppress all messages
@@ -85,7 +83,7 @@ Report bugs to zutils\-bug@nongnu.org
 .br
 Zutils home page: http://www.nongnu.org/zutils/zutils.html
 .SH COPYRIGHT
-Copyright \(co 2019 Antonio Diaz Diaz.
+Copyright \(co 2020 Antonio Diaz Diaz.
 License GPLv2+: GNU GPL version 2 or later <http://gnu.org/licenses/gpl.html>
 .br
 This is free software: you are free to change and redistribute it.
diff --git a/doc/zdiff.1 b/doc/zdiff.1
index 4edcf5e..7d8d387 100644
--- a/doc/zdiff.1
+++ b/doc/zdiff.1
@@ -1,33 +1,32 @@
 .\" DO NOT MODIFY THIS FILE!  It was generated by help2man 1.46.1.
-.TH ZDIFF "1" "January 2019" "zdiff (zutils) 1.8" "User Commands"
+.TH ZDIFF "1" "June 2020" "zdiff (zutils) 1.9" "User Commands"
 .SH NAME
 zdiff \- decompress and compare two files line by line
 .SH SYNOPSIS
 .B zdiff
 [\fI\,options\/\fR] \fI\,file1 \/\fR[\fI\,file2\/\fR]
 .SH DESCRIPTION
-Zdiff compares two files ('\-' means standard input), and if they
-differ, shows the differences line by line. If any given file is
-compressed, its decompressed content is used. Zdiff is a front end to
-the diff program and has the limitation that messages from diff refer to
-temporary filenames instead of those specified.
+zdiff compares two files and, if they differ, writes to standard output the
+differences line by line. A hyphen '\-' used as a file argument means standard
+input. If any file given is compressed, its decompressed content is used.
+zdiff is a front end to the program diff and has the limitation that messages
+from diff refer to temporary file names instead of those specified.
 .PP
-The formats supported are bzip2, gzip, lzip and xz.
+The formats supported are bzip2, gzip, lzip, and xz.
 .PP
-Zdiff compares file1 to file2. If file2 is omitted zdiff tries the
+zdiff compares file1 to file2. The standard input is used only if file1 or
+file2 refers to standard input. If file2 is omitted zdiff tries the
 following:
 .IP
-1. If file1 is compressed, compares its decompressed contents with
+\- If file1 is compressed, compares its decompressed contents with
 the corresponding uncompressed file (the name of file1 with the
 extension removed).
 .IP
-2. If file1 is uncompressed, compares it with the decompressed
+\- If file1 is uncompressed, compares it with the decompressed
 contents of file1.[lz|bz2|gz|xz] (the first one that is found).
-.IP
-3. If no suitable file is found, compares file1 with data read from
-standard input.
 .PP
 Exit status is 0 if inputs are identical, 1 if different, 2 if trouble.
+Some options only work if the diff program used supports them.
 .SH OPTIONS
 .TP
 \fB\-h\fR, \fB\-\-help\fR
@@ -67,7 +66,7 @@ process only the formats in <list>
 don't read runtime configuration file
 .TP
 \fB\-O\fR, \fB\-\-force\-format\fR=\fI\,[\/\fR<f1>][,<f2>]
-force given formats (bz2, gz, lz, xz)
+force the formats given (bz2, gz, lz, xz)
 .TP
 \fB\-p\fR, \fB\-\-show\-c\-function\fR
 show which C function each change is in
@@ -93,6 +92,12 @@ same as \fB\-u\fR but use <n> lines of context
 \fB\-w\fR, \fB\-\-ignore\-all\-space\fR
 ignore all white space
 .TP
+\fB\-W\fR, \fB\-\-width=\fR<n>
+output at most <n> print columns
+.TP
+\fB\-y\fR, \fB\-\-side\-by\-side\fR
+output in two columns
+.TP
 \fB\-\-bz2=\fR<command>
 set compressor and options for bzip2 format
 .TP
@@ -109,7 +114,7 @@ Report bugs to zutils\-bug@nongnu.org
 .br
 Zutils home page: http://www.nongnu.org/zutils/zutils.html
 .SH COPYRIGHT
-Copyright \(co 2019 Antonio Diaz Diaz.
+Copyright \(co 2020 Antonio Diaz Diaz.
 License GPLv2+: GNU GPL version 2 or later <http://gnu.org/licenses/gpl.html>
 .br
 This is free software: you are free to change and redistribute it.
diff --git a/doc/zgrep.1 b/doc/zgrep.1
index 2418ef2..545aea2 100644
--- a/doc/zgrep.1
+++ b/doc/zgrep.1
@@ -1,29 +1,31 @@
 .\" DO NOT MODIFY THIS FILE!  It was generated by help2man 1.46.1.
-.TH ZGREP "1" "January 2019" "zgrep (zutils) 1.8" "User Commands"
+.TH ZGREP "1" "June 2020" "zgrep (zutils) 1.9" "User Commands"
 .SH NAME
 zgrep \- search compressed files for a regular expression
 .SH SYNOPSIS
 .B zgrep
 [\fI\,options\/\fR] \fI\,<pattern> \/\fR[\fI\,files\/\fR]
 .SH DESCRIPTION
-Zgrep is a front end to the grep program that allows transparent search
-on any combination of compressed and uncompressed files. If any given
-file is compressed, its decompressed content is used. If a given file
+zgrep is a front end to the program grep that allows transparent search
+on any combination of compressed and uncompressed files. If any file
+given is compressed, its decompressed content is used. If a file given
 does not exist, and its name does not end with one of the known
 extensions, zgrep tries the compressed file names corresponding to the
-formats supported.
+formats supported. If a file fails to decompress, zgrep continues
+searching the rest of the files.
 .PP
 If a file is specified as '\-', data are read from standard input,
 decompressed if needed, and fed to grep. Data read from standard input
 must be of the same type; all uncompressed or all in the same
-compression format.
+compressed format.
 .PP
 If no files are specified, recursive searches examine the current
 working directory, and nonrecursive searches read standard input.
 .PP
-The formats supported are bzip2, gzip, lzip and xz.
+The formats supported are bzip2, gzip, lzip, and xz.
 .PP
 Exit status is 0 if match, 1 if no match, 2 if trouble.
+Some options only work if the grep program used supports them.
 .SH OPTIONS
 .TP
 \fB\-\-help\fR
@@ -99,7 +101,7 @@ don't read runtime configuration file
 show only the part of a line matching <pattern>
 .TP
 \fB\-O\fR, \fB\-\-force\-format=\fR<fmt>
-force given format (bz2, gz, lz, xz)
+force the format given (bz2, gz, lz, xz)
 .TP
 \fB\-q\fR, \fB\-\-quiet\fR
 suppress all messages
@@ -144,7 +146,7 @@ Report bugs to zutils\-bug@nongnu.org
 .br
 Zutils home page: http://www.nongnu.org/zutils/zutils.html
 .SH COPYRIGHT
-Copyright \(co 2019 Antonio Diaz Diaz.
+Copyright \(co 2020 Antonio Diaz Diaz.
 License GPLv2+: GNU GPL version 2 or later <http://gnu.org/licenses/gpl.html>
 .br
 This is free software: you are free to change and redistribute it.
diff --git a/doc/ztest.1 b/doc/ztest.1
index bffa73f..431e40c 100644
--- a/doc/ztest.1
+++ b/doc/ztest.1
@@ -1,20 +1,24 @@
 .\" DO NOT MODIFY THIS FILE!  It was generated by help2man 1.46.1.
-.TH ZTEST "1" "January 2019" "ztest (zutils) 1.8" "User Commands"
+.TH ZTEST "1" "June 2020" "ztest (zutils) 1.9" "User Commands"
 .SH NAME
 ztest \- verify the integrity of compressed files
 .SH SYNOPSIS
 .B ztest
 [\fI\,options\/\fR] [\fI\,files\/\fR]
 .SH DESCRIPTION
-Ztest verifies the integrity of the specified compressed files.
+ztest verifies the integrity of the compressed files specified.
 Uncompressed files are ignored. If a file is specified as '\-', the
 integrity of compressed data read from standard input is verified. Data
-read from standard input must be all in the same compression format.
+read from standard input must be all in the same compressed format. If
+a file fails to decompress, does not exist, can't be opened, or is a
+terminal, ztest continues verifying the rest of the files. A final
+diagnostic is shown at verbosity level 1 or higher if any file fails the
+test when testing multiple files.
 .PP
 If no files are specified, recursive searches examine the current
 working directory, and nonrecursive searches read standard input.
 .PP
-The formats supported are bzip2, gzip, lzip and xz.
+The formats supported are bzip2, gzip, lzip, and xz.
 .PP
 Note that error detection in the xz format is broken. First, some xz
 files lack integrity information. Second, not all xz decompressors can
@@ -41,7 +45,7 @@ process only the formats in <list>
 don't read runtime configuration file
 .TP
 \fB\-O\fR, \fB\-\-force\-format=\fR<fmt>
-force given format (bz2, gz, lz, xz)
+force the format given (bz2, gz, lz, xz)
 .TP
 \fB\-q\fR, \fB\-\-quiet\fR
 suppress all messages
@@ -71,7 +75,7 @@ Report bugs to zutils\-bug@nongnu.org
 .br
 Zutils home page: http://www.nongnu.org/zutils/zutils.html
 .SH COPYRIGHT
-Copyright \(co 2019 Antonio Diaz Diaz.
+Copyright \(co 2020 Antonio Diaz Diaz.
 License GPLv2+: GNU GPL version 2 or later <http://gnu.org/licenses/gpl.html>
 .br
 This is free software: you are free to change and redistribute it.
diff --git a/doc/zupdate.1 b/doc/zupdate.1
index 955b8c5..afa65d3 100644
--- a/doc/zupdate.1
+++ b/doc/zupdate.1
@@ -1,12 +1,12 @@
 .\" DO NOT MODIFY THIS FILE!  It was generated by help2man 1.46.1.
-.TH ZUPDATE "1" "January 2019" "zupdate (zutils) 1.8" "User Commands"
+.TH ZUPDATE "1" "June 2020" "zupdate (zutils) 1.9" "User Commands"
 .SH NAME
 zupdate \- recompress bzip2, gzip, xz files to lzip format
 .SH SYNOPSIS
 .B zupdate
 [\fI\,options\/\fR] [\fI\,files\/\fR]
 .SH DESCRIPTION
-Zupdate recompresses files from bzip2, gzip, and xz formats to lzip
+zupdate recompresses files from bzip2, gzip, and xz formats to lzip
 format. Each original is compared with the new file and then deleted.
 Only regular files with standard file name extensions are recompressed,
 other files are ignored. Compressed files are decompressed and then
@@ -18,15 +18,18 @@ If no files are specified, recursive searches examine the current
 working directory, and nonrecursive searches do nothing.
 .PP
 If the lzip compressed version of a file already exists, the file is
-skipped unless the '\-\-force' option is given. In this case, if the
+skipped unless the option '\-\-force' is given. In this case, if the
 comparison with the existing lzip version fails, an error is returned
 and the original file is not deleted. The operation of zupdate is meant
-to be safe and not produce any data loss. Therefore, existing lzip
+to be safe and not cause any data loss. Therefore, existing lzip
 compressed files are never overwritten nor deleted.
 .PP
-Exit status is 0 if all the compressed files were successfully
-recompressed (if needed), compared and deleted (if requested). Non\-zero
-otherwise.
+The names of the original files must have one of the following extensions:
+\&'.bz2', '.gz', and '.xz' are recompressed to '.lz'.
+\&'.tbz', '.tbz2', '.tgz', and '.txz' are recompressed to '.tlz'.
+.PP
+Exit status is 0 if all the compressed files were successfully recompressed
+(if needed), compared, and deleted (if requested). Non\-zero otherwise.
 .SH OPTIONS
 .TP
 \fB\-h\fR, \fB\-\-help\fR
@@ -42,7 +45,7 @@ don't skip a file even if the .lz exists
 keep (don't delete) input files
 .TP
 \fB\-l\fR, \fB\-\-lzip\-verbose\fR
-pass a \fB\-v\fR option to the lzip compressor
+pass one option \fB\-v\fR to the lzip compressor
 .TP
 \fB\-M\fR, \fB\-\-format=\fR<list>
 process only the formats in <list>
@@ -81,7 +84,7 @@ Report bugs to zutils\-bug@nongnu.org
 .br
 Zutils home page: http://www.nongnu.org/zutils/zutils.html
 .SH COPYRIGHT
-Copyright \(co 2019 Antonio Diaz Diaz.
+Copyright \(co 2020 Antonio Diaz Diaz.
 License GPLv2+: GNU GPL version 2 or later <http://gnu.org/licenses/gpl.html>
 .br
 This is free software: you are free to change and redistribute it.
diff --git a/doc/zutils.info b/doc/zutils.info
index bf99e2d..2de6d3b 100644
--- a/doc/zutils.info
+++ b/doc/zutils.info
@@ -1,5 +1,4 @@
-This is zutils.info, produced by makeinfo version 4.13+ from
-zutils.texi.
+This is zutils.info, produced by makeinfo version 4.13+ from zutils.texi.
 
 INFO-DIR-SECTION Data Compression
 START-INFO-DIR-ENTRY
@@ -12,7 +11,7 @@ File: zutils.info,  Node: Top,  Next: Introduction,  Up: (dir)
 Zutils Manual
 *************
 
-This manual is for Zutils (version 1.8, 1 January 2019).
+This manual is for Zutils (version 1.9, 27 June 2020).
 
 * Menu:
 
@@ -29,10 +28,10 @@ This manual is for Zutils (version 1.8, 1 January 2019).
 * Concept index::       Index of concepts
 
 
-   Copyright (C) 2009-2019 Antonio Diaz Diaz.
+   Copyright (C) 2009-2020 Antonio Diaz Diaz.
 
-   This manual is free documentation: you have unlimited permission to
-copy, distribute and modify it.
+   This manual is free documentation: you have unlimited permission to copy,
+distribute, and modify it.
 
 
 File: zutils.info,  Node: Introduction,  Next: Common options,  Prev: Top,  Up: Top
@@ -41,45 +40,45 @@ File: zutils.info,  Node: Introduction,  Next: Common options,  Prev: Top,  Up:
 **************
 
 Zutils is a collection of utilities able to process any combination of
-compressed and uncompressed files transparently. If any given file,
-including standard input, is compressed, its decompressed content is
-used. Compressed files are decompressed on the fly; no temporary files
-are created.
+compressed and uncompressed files transparently. If any file given,
+including standard input, is compressed, its decompressed content is used.
+Compressed files are decompressed on the fly; no temporary files are
+created.
 
-   These utilities are not wrapper scripts but safer and more efficient
-C++ programs. In particular the '--recursive' option is very efficient
-in those utilities supporting it.
+   These utilities are not wrapper scripts but safer and more efficient C++
+programs. In particular the option '--recursive' is very efficient in those
+utilities supporting it.
 
-The utilities provided are zcat, zcmp, zdiff, zgrep, ztest and zupdate.
-The formats supported are bzip2, gzip, lzip and xz.
-Zutils uses external compressors. The compressor to be used for each
-format is configurable at runtime.
+The utilities provided are zcat, zcmp, zdiff, zgrep, ztest, and zupdate.
+The formats supported are bzip2, gzip, lzip, and xz.
+Zutils uses external compressors. The compressor to be used for each format
+is configurable at runtime.
 
    zcat, zcmp, zdiff, and zgrep are improved replacements for the shell
-scripts provided by GNU gzip. ztest is unique to zutils. zupdate is
-similar to gzip's znew.
+scripts provided by GNU gzip. ztest is unique to zutils. zupdate is similar
+to gzip's znew.
 
-   NOTE: Bzip2 and lzip provide well-defined values of exit status,
-which makes them safe to use with zutils. Gzip and xz may return
-ambiguous warning values, making them less reliable back ends for
-zutils.  *Note compressor-requirements::.
+   NOTE: Bzip2 and lzip provide well-defined values of exit status, which
+makes them safe to use with zutils. Gzip and xz may return ambiguous warning
+values, making them less reliable back ends for zutils. *Note
+compressor-requirements::.
 
-   FORMAT NOTE 1: The '--format' option allows the processing of a
-subset of formats in recursive mode and when trying compressed file
-names: 'zgrep foo -r --format=bz2,lz somedir somefile.tar'.
+   FORMAT NOTE 1: The option '--format' allows the processing of a subset
+of formats in recursive mode and when trying compressed file names:
+'zgrep foo -r --format=bz2,lz somedir somefile.tar'.
 
-   FORMAT NOTE 2: If the '--force-format' option is given, the files
-are passed to the corresponding decompressor without verifying their
-format, allowing for example the processing of compress'd (.Z) files
-with gzip: 'zcmp --force-format=gz file.Z file.lz'.
+   FORMAT NOTE 2: If the option '--force-format' is given, the files are
+passed to the corresponding decompressor without verifying their format,
+allowing for example the processing of compress'd (.Z) files with gzip:
+'zcmp --force-format=gz file.Z file.lz'.
 
-   LANGUAGE NOTE: Uncompressed = not compressed = plain data; it may
-never have been compressed. Decompressed is used to refer to data which
-have undergone the process of decompression.
+   LANGUAGE NOTE: Uncompressed = not compressed = plain data; it may never
+have been compressed. Decompressed is used to refer to data which have
+undergone the process of decompression.
 
 
-   Numbers given as arguments to options (positions, sizes) may be
-followed by a multiplier and an optional 'B' for "byte".
+   Numbers given as arguments to options (positions, sizes) may be followed
+by a multiplier and an optional 'B' for "byte".
 
    Table of SI and binary prefixes (unit multipliers):
 
@@ -99,9 +98,9 @@ File: zutils.info,  Node: Common options,  Next: The zutilsrc file,  Prev: Intro
 2 Common options
 ****************
 
-The following options are available in all the utilities. Rather than
-writing identical descriptions for each of the programs, they are
-described here.
+The following options: are available in all the utilities. Rather than
+writing identical descriptions for each of the programs, they are described
+here. *Note Argument syntax: (arg_parser)Argument syntax.
 
 '-h'
 '--help'
@@ -110,19 +109,19 @@ described here.
 
 '-V'
 '--version'
-     Print the version number on the standard output and exit.  This
-     version number should be included in all bug reports.
+     Print the version number on the standard output and exit. This version
+     number should be included in all bug reports.
 
 '-M FORMAT_LIST'
 '--format=FORMAT_LIST'
-     Process only the formats listed in the comma-separated
-     FORMAT_LIST. Valid formats are 'bz2', 'gz', 'lz', 'xz' and 'un'
-     for 'uncompressed', meaning "any file name without a known
-     extension". This option excludes files based on extension, instead
-     of format, because it is more efficient. The exclusion only
-     applies to names generated automatically (for example when adding
-     extensions to a file name or when operating recursively on
-     directories). Files given in the command line are always processed.
+     Process only the formats listed in the comma-separated FORMAT_LIST.
+     Valid formats are 'bz2', 'gz', 'lz', 'xz', and 'un' for
+     'uncompressed', meaning "any file name without a known extension".
+     This option excludes files based on extension, instead of format,
+     because it is more efficient. The exclusion only applies to names
+     generated automatically (for example when adding extensions to a file
+     name or when operating recursively on directories). Files given in the
+     command line are always processed.
 
      Each format in FORMAT_LIST enables file names with the following
      extensions:
@@ -141,17 +140,20 @@ described here.
 '--gz=COMMAND'
 '--lz=COMMAND'
 '--xz=COMMAND'
-     Set program (may include arguments) to be used as (de)compressor
-     for the given format. The name of the program can't begin with
-     '-'. These options override the values set in 'zutilsrc'. The
-     compression program used must meet three requirements:
+     Set program to be used as (de)compressor for the corresponding format.
+     COMMAND may include arguments. For example '--lz='plzip --threads=2''.
+     The program set with '--lz' is used for both compression and
+     decompression. The other three are used only for decompression. The
+     name of the program can't begin with '-'. These options override the
+     values set in 'zutilsrc'. The compression program used must meet three
+     requirements:
 
-       1. When called with the '-d' option, it must read compressed
-          data from the standard input and produce decompressed data on
-          the standard output.
+       1. When called with the option '-d', it must read compressed data
+          from the standard input and produce decompressed data on the
+          standard output.
 
-       2. If the '-q' option is passed to zutils, the compression
-          program must also accept it.
+       2. If the option '-q' is passed to zutils, the compression program
+          must also accept it.
 
        3. It must return 0 if no errors occurred, and a non-zero value
           otherwise.
@@ -164,23 +166,23 @@ File: zutils.info,  Node: The zutilsrc file,  Next: Zcat,  Prev: Common options,
 *******************
 
 'zutilsrc' is the runtime configuration file for zutils. In it you may
-define the compressor name and options to be used for each format.  The
-'zutilsrc' file is optional; you don't need to install it in order to
-run zutils.
+define the compressor name and options to be used for each format. The
+'zutilsrc' file is optional; you don't need to install it in order to run
+zutils.
 
-   The compressors specified in the command line override those
-specified in the 'zutilsrc' file.
+   The compressors specified in the command line override those specified
+in the 'zutilsrc' file.
 
    You may copy the system 'zutilsrc' file '${sysconfdir}/zutilsrc' to
-'$HOME/.zutilsrc' and customize these options as you like. The file
-syntax is fairly obvious (and there are further instructions in it):
+'$HOME/.zutilsrc' and customize these options as you like. The file syntax
+is fairly obvious (and there are further instructions in it):
 
   1. Any line beginning with '#' is a comment line.
 
-  2. Each non-comment line defines the command to be used for the given
-     format, with the syntax:
+  2. Each non-comment line defines the command to be used for the
+     corresponding format, with the syntax:
           <format> = <compressor> [options]
-     where <format> is one of 'bz2', 'gz', 'lz' or 'xz'.
+     where <format> is one of 'bz2', 'gz', 'lz', or 'xz'.
 
 
 File: zutils.info,  Node: Zcat,  Next: Zcmp,  Prev: The zutilsrc file,  Up: Top
@@ -188,26 +190,26 @@ File: zutils.info,  Node: Zcat,  Next: Zcmp,  Prev: The zutilsrc file,  Up: Top
 4 Zcat
 ******
 
-zcat copies each given file to standard output. If any given file is
-compressed, its decompressed content is used. If a given file does not
-exist, and its name does not end with one of the known extensions, zcat
-tries the compressed file names corresponding to the formats supported.
-If a file fails to decompress, zcat continues copying the rest of the
-files.
+zcat copies each FILE argument to standard output in sequence. If any file
+given is compressed, its decompressed content is copied. If a file given
+does not exist, and its name does not end with one of the known extensions,
+zcat tries the compressed file names corresponding to the formats
+supported. If a file fails to decompress, zcat continues copying the rest
+of the files.
 
    If a file is specified as '-', data are read from standard input,
 decompressed if needed, and sent to standard output. Data read from
 standard input must be of the same type; all uncompressed or all in the
-same compression format.
+same compressed format.
 
-   If no files are specified, recursive searches examine the current
-working directory, and nonrecursive searches read standard input.
+   If no files are specified, recursive searches examine the current working
+directory, and nonrecursive searches read standard input.
 
    The format for running zcat is:
 
      zcat [OPTIONS] [FILES]
 
-Exit status is 0 if no errors occurred, non-zero otherwise.
+Exit status is 0 if no errors occurred, 1 otherwise.
 
    zcat supports the following options:
 
@@ -217,8 +219,8 @@ Exit status is 0 if no errors occurred, non-zero otherwise.
 
 '-b'
 '--number-nonblank'
-     Number all nonblank output lines, starting with 1. The line count
-     is unlimited.
+     Number all nonblank output lines, starting with 1. The line count is
+     unlimited.
 
 '-e'
      Equivalent to '-vE'.
@@ -229,16 +231,14 @@ Exit status is 0 if no errors occurred, non-zero otherwise.
 
 '-n'
 '--number'
-     Number all output lines, starting with 1. The line count is
-     unlimited.
+     Number all output lines, starting with 1. The line count is unlimited.
 
 '-O FORMAT'
 '--force-format=FORMAT'
-     Force the given compression format. Valid values for FORMAT are
-     'bz2', 'gz', 'lz' and 'xz'. If this option is used, the files are
-     passed to the corresponding decompressor without verifying their
-     format, and the exact file name must be given. Other names won't
-     be tried.
+     Force the compressed format given. Valid values for FORMAT are 'bz2',
+     'gz', 'lz', and 'xz'. If this option is used, the files are passed to
+     the corresponding decompressor without verifying their format, and the
+     exact file name must be given. Other names won't be tried.
 
 '-q'
 '--quiet'
@@ -247,8 +247,8 @@ Exit status is 0 if no errors occurred, non-zero otherwise.
 '-r'
 '--recursive'
      For each directory operand, read and process all files in that
-     directory, recursively. Follow symbolic links in the command line,
-     but skip symlinks that are encountered recursively.
+     directory, recursively. Follow symbolic links given in the command
+     line, but skip symbolic links that are encountered recursively.
 
 '-R'
 '--dereference-recursive'
@@ -282,28 +282,27 @@ File: zutils.info,  Node: Zcmp,  Next: Zdiff,  Prev: Zcat,  Up: Top
 5 Zcmp
 ******
 
-zcmp compares two files ('-' means standard input), and if they differ,
-tells the first byte and line number where they differ. Bytes and lines
-are numbered starting with 1. If any given file is compressed, its
-decompressed content is used. Compressed files are decompressed on the
-fly; no temporary files are created.
+zcmp compares two files and, if they differ, writes to standard output the
+first byte and line number where they differ. Bytes and lines are numbered
+starting with 1. A hyphen '-' used as a FILE argument means standard input.
+If any file given is compressed, its decompressed content is used.
+Compressed files are decompressed on the fly; no temporary files are
+created.
 
    The format for running zcmp is:
 
      zcmp [OPTIONS] FILE1 [FILE2]
 
-This compares FILE1 to FILE2. If FILE2 is omitted zcmp tries the
+This compares FILE1 to FILE2. The standard input is used only if FILE1 or
+FILE2 refers to standard input. If FILE2 is omitted zcmp tries the
 following:
 
-  1. If FILE1 is compressed, compares its decompressed contents with
-     the corresponding uncompressed file (the name of FILE1 with the
-     extension removed).
+   - If FILE1 is compressed, compares its decompressed contents with the
+     corresponding uncompressed file (the name of FILE1 with the extension
+     removed).
 
-  2. If FILE1 is uncompressed, compares it with the decompressed
-     contents of FILE1.[lz|bz2|gz|xz] (the first one that is found).
-
-  3. If no suitable file is found, compares FILE1 with data read from
-     standard input.
+   - If FILE1 is uncompressed, compares it with the decompressed contents
+     of FILE1.[lz|bz2|gz|xz] (the first one that is found).
 
 An exit status of 0 means no differences were found, 1 means some
 differences were found, and 2 means trouble.
@@ -312,17 +311,16 @@ differences were found, and 2 means trouble.
 
 '-b'
 '--print-bytes'
-     Print the differing bytes. Print control bytes as a '^' followed by
-     a letter, and precede bytes larger than 127 with 'M-' (which stands
-     for "meta").
+     Print the differing bytes. Print control bytes as a '^' followed by a
+     letter, and precede bytes larger than 127 with 'M-' (which stands for
+     "meta").
 
 '-i SIZE'
 '--ignore-initial=SIZE'
      Ignore any differences in the first SIZE bytes of the input files.
-     Treat files with fewer than SIZE bytes as if they were empty. If
-     SIZE is in the form 'SIZE1:SIZE2', ignore the first SIZE1 bytes of
-     the first input file and the first SIZE2 bytes of the second input
-     file.
+     Treat files with fewer than SIZE bytes as if they were empty. If SIZE
+     is in the form 'SIZE1:SIZE2', ignore the first SIZE1 bytes of the
+     first input file and the first SIZE2 bytes of the second input file.
 
 '-l'
 '-v'
@@ -337,20 +335,20 @@ differences were found, and 2 means trouble.
 
 '-O [FORMAT1][,FORMAT2]'
 '--force-format=[FORMAT1][,FORMAT2]'
-     Force the given compression formats. Any of FORMAT1 or FORMAT2 may
-     be omitted and the corresponding format will be automatically
-     detected. Valid values for FORMAT are 'bz2', 'gz', 'lz' and 'xz'.
-     If at least one format is specified with this option, the file is
-     passed to the corresponding decompressor without verifying its
-     format, and the exact file names of both FILE1 and FILE2 must be
-     given. Other names won't be tried.
+     Force the compressed formats given. Any of FORMAT1 or FORMAT2 may be
+     omitted and the corresponding format will be automatically detected.
+     Valid values for FORMAT are 'bz2', 'gz', 'lz', and 'xz'. If at least
+     one format is specified with this option, the file is passed to the
+     corresponding decompressor without verifying its format, and the exact
+     file names of both FILE1 and FILE2 must be given. Other names won't be
+     tried.
 
 '-q'
 '-s'
 '--quiet'
 '--silent'
-     Don't print anything; only return an exit status indicating
-     whether the files differ.
+     Don't print anything; only return an exit status indicating whether the
+     files differ.
 
 
 
@@ -359,34 +357,33 @@ File: zutils.info,  Node: Zdiff,  Next: Zgrep,  Prev: Zcmp,  Up: Top
 6 Zdiff
 *******
 
-zdiff compares two files ('-' means standard input), and if they
-differ, shows the differences line by line. If any given file is
-compressed, its decompressed content is used. zdiff is a front end to
-the diff program and has the limitation that messages from diff refer to
-temporary file names instead of those specified.
+zdiff compares two files and, if they differ, writes to standard output the
+differences line by line. A hyphen '-' used as a FILE argument means
+standard input. If any file given is compressed, its decompressed content
+is used. zdiff is a front end to the program diff and has the limitation
+that messages from diff refer to temporary file names instead of those
+specified.
 
    The format for running zdiff is:
 
      zdiff [OPTIONS] FILE1 [FILE2]
 
-This compares FILE1 to FILE2. If FILE2 is omitted zdiff tries the
+This compares FILE1 to FILE2. The standard input is used only if FILE1 or
+FILE2 refers to standard input. If FILE2 is omitted zdiff tries the
 following:
 
-  1. If FILE1 is compressed, compares its decompressed contents with
-     the corresponding uncompressed file (the name of FILE1 with the
-     extension removed).
+   - If FILE1 is compressed, compares its decompressed contents with the
+     corresponding uncompressed file (the name of FILE1 with the extension
+     removed).
 
-  2. If FILE1 is uncompressed, compares it with the decompressed
-     contents of FILE1.[lz|bz2|gz|xz] (the first one that is found).
-
-  3. If no suitable file is found, compares FILE1 with data read from
-     standard input.
+   - If FILE1 is uncompressed, compares it with the decompressed contents
+     of FILE1.[lz|bz2|gz|xz] (the first one that is found).
 
 An exit status of 0 means no differences were found, 1 means some
 differences were found, and 2 means trouble.
 
-   zdiff supports the following options (some options only work if the
-diff program used supports them):
+   zdiff supports the following options (some options only work if the diff
+program used supports them):
 
 '-a'
 '--text'
@@ -421,13 +418,13 @@ diff program used supports them):
 
 '-O [FORMAT1][,FORMAT2]'
 '--force-format=[FORMAT1][,FORMAT2]'
-     Force the given compression formats. Any of FORMAT1 or FORMAT2 may
-     be omitted and the corresponding format will be automatically
-     detected. Valid values for FORMAT are 'bz2', 'gz', 'lz' and 'xz'.
-     If at least one format is specified with this option, the file is
-     passed to the corresponding decompressor without verifying its
-     format, and the exact file names of both FILE1 and FILE2 must be
-     given. Other names won't be tried.
+     Force the compressed formats given. Any of FORMAT1 or FORMAT2 may be
+     omitted and the corresponding format will be automatically detected.
+     Valid values for FORMAT are 'bz2', 'gz', 'lz', and 'xz'. If at least
+     one format is specified with this option, the file is passed to the
+     corresponding decompressor without verifying its format, and the exact
+     file names of both FILE1 and FILE2 must be given. Other names won't be
+     tried.
 
 '-p'
 '--show-c-function'
@@ -467,31 +464,29 @@ File: zutils.info,  Node: Zgrep,  Next: Ztest,  Prev: Zdiff,  Up: Top
 7 Zgrep
 *******
 
-zgrep is a front end to the grep program that allows transparent search
-on any combination of compressed and uncompressed files. If any given
-file is compressed, its decompressed content is used. If a given file
-does not exist, and its name does not end with one of the known
-extensions, zgrep tries the compressed file names corresponding to the
-formats supported. If a file fails to decompress, zgrep continues
-searching the rest of the files.
+zgrep is a front end to the program grep that allows transparent search on
+any combination of compressed and uncompressed files. If any file given is
+compressed, its decompressed content is used. If a file given does not
+exist, and its name does not end with one of the known extensions, zgrep
+tries the compressed file names corresponding to the formats supported. If
+a file fails to decompress, zgrep continues searching the rest of the files.
 
    If a file is specified as '-', data are read from standard input,
-decompressed if needed, and fed to grep. Data read from standard input
-must be of the same type; all uncompressed or all in the same
-compression format.
+decompressed if needed, and fed to grep. Data read from standard input must
+be of the same type; all uncompressed or all in the same compressed format.
 
-   If no files are specified, recursive searches examine the current
-working directory, and nonrecursive searches read standard input.
+   If no files are specified, recursive searches examine the current working
+directory, and nonrecursive searches read standard input.
 
    The format for running zgrep is:
 
      zgrep [OPTIONS] PATTERN [FILES]
 
-An exit status of 0 means at least one match was found, 1 means no
-matches were found, and 2 means trouble.
+An exit status of 0 means at least one match was found, 1 means no matches
+were found, and 2 means trouble.
 
-   zgrep supports the following options (some options only work if the
-grep program used supports them):
+   zgrep supports the following options (some options only work if the grep
+program used supports them):
 
 '-a'
 '--text'
@@ -518,7 +513,7 @@ grep program used supports them):
      Print N lines of output context.
 
 '--color[=WHEN]'
-     Show matched strings in color. WHEN is 'never', 'always' or 'auto'.
+     Show matched strings in color. WHEN is 'never', 'always', or 'auto'.
 
 '-e PATTERN'
 '--regexp=PATTERN'
@@ -531,9 +526,9 @@ grep program used supports them):
 '-f FILE'
 '--file=FILE'
      Obtain patterns from FILE, one per line.
-     When searching in several files at once, command substitution can
-     be used with '-e' to read FILE only once, for example if FILE is
-     not a regular file: 'zgrep -e "$(cat FILE)" file1.lz file2.gz'
+     When searching in several files at once, command substitution can be
+     used with '-e' to read FILE only once, for example if FILE is not a
+     regular file: 'zgrep -e "$(cat FILE)" file1.lz file2.gz'
 
 '-F'
 '--fixed-strings'
@@ -541,8 +536,8 @@ grep program used supports them):
 
 '-h'
 '--no-filename'
-     Suppress the prefixing of file names on output when multiple files
-     are searched.
+     Suppress the prefixing of file names on output when multiple files are
+     searched.
 
 '-H'
 '--with-filename'
@@ -577,22 +572,21 @@ grep program used supports them):
 
 '-O FORMAT'
 '--force-format=FORMAT'
-     Force the given compression format. Valid values for FORMAT are
-     'bz2', 'gz', 'lz' and 'xz'. If this option is used, the files are
-     passed to the corresponding decompressor without verifying their
-     format, and the exact file name must be given. Other names won't
-     be tried.
+     Force the compressed format given. Valid values for FORMAT are 'bz2',
+     'gz', 'lz', and 'xz'. If this option is used, the files are passed to
+     the corresponding decompressor without verifying their format, and the
+     exact file name must be given. Other names won't be tried.
 
 '-q'
 '--quiet'
-     Suppress all messages. Exit immediately with zero status if any
-     match is found, even if an error was detected.
+     Suppress all messages. Exit immediately with zero status if any match
+     is found, even if an error was detected.
 
 '-r'
 '--recursive'
      For each directory operand, read and process all files in that
-     directory, recursively. Follow symbolic links in the command line,
-     but skip symlinks that are encountered recursively.
+     directory, recursively. Follow symbolic links given in the command
+     line, but skip symbolic links that are encountered recursively.
 
 '-R'
 '--dereference-recursive'
@@ -625,42 +619,43 @@ File: zutils.info,  Node: Ztest,  Next: Zupdate,  Prev: Zgrep,  Up: Top
 8 Ztest
 *******
 
-ztest verifies the integrity of the specified compressed files.
+ztest verifies the integrity of the compressed files specified.
 Uncompressed files are ignored. If a file is specified as '-', the
 integrity of compressed data read from standard input is verified. Data
-read from standard input must be all in the same compression format. If
-a file fails to decompress, ztest continues verifying the rest of the
-files.
+read from standard input must be all in the same compressed format. If a
+file fails to decompress, does not exist, can't be opened, or is a
+terminal, ztest continues verifying the rest of the files. A final
+diagnostic is shown at verbosity level 1 or higher if any file fails the
+test when testing multiple files.
 
-   If no files are specified, recursive searches examine the current
-working directory, and nonrecursive searches read standard input.
+   If no files are specified, recursive searches examine the current working
+directory, and nonrecursive searches read standard input.
 
    Note that error detection in the xz format is broken. First, some xz
 files lack integrity information. Second, not all xz decompressors can
-verify the integrity of all xz files. Third, section 2.1.1.2 'Stream
-Flags' of the xz format specification allows xz decompressors to
-produce garbage output without issuing any warning. Therefore, xz files
-can't always be verified as reliably as files in the other formats can.
+verify the integrity of all xz files. Third, section 2.1.1.2 'Stream Flags'
+of the xz format specification allows xz decompressors to produce garbage
+output without issuing any warning. Therefore, xz files can't always be
+verified as reliably as files in the other formats can.
 
    The format for running ztest is:
 
      ztest [OPTIONS] [FILES]
 
-The exit status is 0 if all compressed files verify OK, 1 if
-environmental problems (file not found, invalid flags, I/O errors, etc),
-2 if any compressed file is corrupt or invalid.
+The exit status is 0 if all compressed files verify OK, 1 if environmental
+problems (file not found, invalid flags, I/O errors, etc), 2 if any
+compressed file is corrupt or invalid.
 
    ztest supports the following options:
 
 '-O FORMAT'
 '--force-format=FORMAT'
-     Force the given compression format. Valid values for FORMAT are
-     'bz2', 'gz', 'lz' and 'xz'. If this option is used, the files are
-     passed to the corresponding decompressor without verifying their
-     format, and any files in a format that the decompressor can't
-     understand will fail. For example, '--force-format=gz' can test
-     gzipped (.gz) and compress'd (.Z) files if the compressor used is
-     GNU gzip.
+     Force the compressed format given. Valid values for FORMAT are 'bz2',
+     'gz', 'lz', and 'xz'. If this option is used, the files are passed to
+     the corresponding decompressor without verifying their format, and any
+     files in a format that the decompressor can't understand will fail.
+     For example, '--force-format=gz' can test gzipped (.gz) and compress'd
+     (.Z) files if the compressor used is GNU gzip.
 
 '-q'
 '--quiet'
@@ -669,8 +664,8 @@ environmental problems (file not found, invalid flags, I/O errors, etc),
 '-r'
 '--recursive'
      For each directory operand, read and process all files in that
-     directory, recursively. Follow symbolic links in the command line,
-     but skip symlinks that are encountered recursively.
+     directory, recursively. Follow symbolic links given in the command
+     line, but skip symbolic links that are encountered recursively.
 
 '-R'
 '--dereference-recursive'
@@ -689,68 +684,69 @@ File: zutils.info,  Node: Zupdate,  Next: Problems,  Prev: Ztest,  Up: Top
 9 Zupdate
 *********
 
-zupdate recompresses files from bzip2, gzip, and xz formats to lzip
-format. Each original is compared with the new file and then deleted.
-Only regular files with standard file name extensions are recompressed,
-other files are ignored. Compressed files are decompressed and then
-recompressed on the fly; no temporary files are created. If an error
-happens while recompressing a file, zupdate exits immediately without
-recompressing the rest of the files. The lzip format is chosen as
-destination because it is the most appropriate for long-term data
-archiving.
+zupdate recompresses files from bzip2, gzip, and xz formats to lzip format.
+Each original is compared with the new file and then deleted. Only regular
+files with standard file name extensions are recompressed, other files are
+ignored. Compressed files are decompressed and then recompressed on the fly;
+no temporary files are created. If an error happens while recompressing a
+file, zupdate exits immediately without recompressing the rest of the files.
+The lzip format is chosen as destination because it is the most appropriate
+for long-term data archiving.
 
-   If no files are specified, recursive searches examine the current
-working directory, and nonrecursive searches do nothing.
+   If no files are specified, recursive searches examine the current working
+directory, and nonrecursive searches do nothing.
 
    If the lzip compressed version of a file already exists, the file is
-skipped unless the '--force' option is given. In this case, if the
-comparison with the existing lzip version fails, an error is returned
-and the original file is not deleted. The operation of zupdate is meant
-to be safe and not produce any data loss. Therefore, existing lzip
-compressed files are never overwritten nor deleted.
+skipped unless the option '--force' is given. In this case, if the
+comparison with the existing lzip version fails, an error is returned and
+the original file is not deleted. The operation of zupdate is meant to be
+safe and not cause any data loss. Therefore, existing lzip compressed files
+are never overwritten nor deleted.
 
-   Combining the '--force' and '--keep' options, as in
-'zupdate -f -k *.gz', verifies that there are no differences between
-each pair of files in a multiformat set of files.
+   Combining the options '--force' and '--keep', as in
+'zupdate -f -k *.gz', verifies that there are no differences between each
+pair of files in a multiformat set of files.
 
    The names of the original files must have one of the following
-extensions: '.bz2', '.tbz', '.tbz2', '.gz', '.tgz', '.xz', '.txz'. The
-files produced have the extensions '.lz' or '.tar.lz'.
-
-   Recompressing a file is much like copying or moving it; therefore
-zupdate preserves the access and modification dates, permissions, and,
-when possible, ownership of the file just as 'cp -p' does. (If the user
-ID or the group ID can't be duplicated, the file permission bits S_ISUID
-and S_ISGID are cleared).
+extensions:
+'.bz2', '.gz', and '.xz' are recompressed to '.lz'.
+'.tbz', '.tbz2', '.tgz', and '.txz' are recompressed to '.tlz'.
+Keeping the combined extensions ('.tgz' -> '.tlz') may be useful when
+recompressing Slackware packages, for example.
+
+   Recompressing a file is much like copying or moving it; therefore zupdate
+preserves the access and modification dates, permissions, and, when
+possible, ownership of the file just as 'cp -p' does. (If the user ID or
+the group ID can't be duplicated, the file permission bits S_ISUID and
+S_ISGID are cleared).
 
    The format for running zupdate is:
 
      zupdate [OPTIONS] [FILES]
 
-Exit status is 0 if all the compressed files were successfully
-recompressed (if needed), compared and deleted (if requested). Non-zero
-otherwise.
+Exit status is 0 if all the compressed files were successfully recompressed
+(if needed), compared, and deleted (if requested). Non-zero otherwise.
 
    zupdate supports the following options:
 
 '-f'
 '--force'
-     Don't skip a file for which a lzip compressed version already
-     exists.  '--force' compares the content of the input file with the
-     content of the existing lzip file and deletes the input file if
-     both contents are identical.
+     Don't skip a file for which a lzip compressed version already exists.
+     '--force' compares the content of the input file with the content of
+     the existing lzip file and deletes the input file if both contents are
+     identical.
 
 '-k'
 '--keep'
-     Keep (don't delete) the input file after comparing it with the
-     lzip file.
+     Keep (don't delete) the input file after comparing it with the lzip
+     file.
 
 '-l'
 '--lzip-verbose'
-     Pass a '-v' option to the lzip compressor so that it shows the
-     compression ratio for each file processed. Using lzip 1.15 and
-     newer, a second '-l' shows the progress of compression. Use it
-     together with '-v' to see the name of the file.
+     Pass one option '-v' to the lzip compressor so that it shows the
+     compression ratio for each file processed. Using lzip 1.15 or newer, a
+     second '-l' shows the progress of compression. Use it together with
+     '-v' to see the name of the file.
 
 '-q'
 '--quiet'
@@ -759,8 +755,8 @@ otherwise.
 '-r'
 '--recursive'
      For each directory operand, read and process all files in that
-     directory, recursively. Follow symbolic links in the command line,
-     but skip symlinks that are encountered recursively.
+     directory, recursively. Follow symbolic links given in the command
+     line, but skip symbolic links that are encountered recursively.
 
 '-R'
 '--dereference-recursive'
@@ -769,12 +765,13 @@ otherwise.
 
 '-v'
 '--verbose'
-     Verbose mode. Show the files being processed. A second '-v' also
-     shows the files being ignored.
+     Verbose mode. Show the files being processed. A second '-v' also shows
+     the files being ignored.
 
 '-0 .. -9'
-     Set the compression level of lzip. By default zupdate passes '-9'
-     to lzip.
+     Set the compression level of lzip. By default zupdate passes '-9' to
+     lzip. Custom compression options can be passed to lzip with the option
+     '--lz'. For example '--lz='lzip -9 -s64MiB''.
 
 
 
@@ -783,14 +780,14 @@ File: zutils.info,  Node: Problems,  Next: Concept index,  Prev: Zupdate,  Up: T
 10 Reporting bugs
 *****************
 
-There are probably bugs in zutils. There are certainly errors and
-omissions in this manual. If you report them, they will get fixed. If
-you don't, no one will ever know about them and they will remain unfixed
-for all eternity, if not longer.
+There are probably bugs in zutils. There are certainly errors and omissions
+in this manual. If you report them, they will get fixed. If you don't, no
+one will ever know about them and they will remain unfixed for all
+eternity, if not longer.
 
    If you find a bug in zutils, please send electronic mail to
-<zutils-bug@nongnu.org>. Include the version number, which you can find
-by running 'zupdate --version'.
+<zutils-bug@nongnu.org>. Include the version number, which you can find by
+running 'zupdate --version'.
 
 
 File: zutils.info,  Node: Concept index,  Prev: Problems,  Up: Top
@@ -801,34 +798,34 @@ Concept index
 
 * Menu:
 
-* bugs:                                  Problems.              (line 6)
-* common options:                        Common options.        (line 6)
-* getting help:                          Problems.              (line 6)
-* introduction:                          Introduction.          (line 6)
-* the zutilsrc file:                     The zutilsrc file.     (line 6)
-* zcat:                                  Zcat.                  (line 6)
-* zcmp:                                  Zcmp.                  (line 6)
-* zdiff:                                 Zdiff.                 (line 6)
-* zgrep:                                 Zgrep.                 (line 6)
-* ztest:                                 Ztest.                 (line 6)
-* zupdate:                               Zupdate.               (line 6)
+* bugs:                                  Problems.                  (line 6)
+* common options:                        Common options.            (line 6)
+* getting help:                          Problems.                  (line 6)
+* introduction:                          Introduction.              (line 6)
+* the zutilsrc file:                     The zutilsrc file.         (line 6)
+* zcat:                                  Zcat.                      (line 6)
+* zcmp:                                  Zcmp.                      (line 6)
+* zdiff:                                 Zdiff.                     (line 6)
+* zgrep:                                 Zgrep.                     (line 6)
+* ztest:                                 Ztest.                     (line 6)
+* zupdate:                               Zupdate.                   (line 6)
 
 
 
 Tag Table:
 Node: Top222
-Node: Introduction1149
+Node: Introduction1148
 Node: Common options3773
-Ref: compressor-requirements5596
-Node: The zutilsrc file5968
-Node: Zcat6893
-Node: Zcmp9445
-Node: Zdiff11904
-Node: Zgrep14608
-Node: Ztest18603
-Node: Zupdate20938
-Node: Problems24364
-Node: Concept index24898
+Ref: compressor-requirements5844
+Node: The zutilsrc file6216
+Node: Zcat7149
+Node: Zcmp9712
+Node: Zdiff12202
+Node: Zgrep14942
+Node: Ztest18944
+Node: Zupdate21451
+Node: Problems25123
+Node: Concept index25657
 
 End Tag Table
 
diff --git a/doc/zutils.texi b/doc/zutils.texi
index 789643a..bb1c3b1 100644
--- a/doc/zutils.texi
+++ b/doc/zutils.texi
@@ -6,8 +6,8 @@
 @finalout
 @c %**end of header
 
-@set UPDATED 1 January 2019
-@set VERSION 1.8
+@set UPDATED 27 June 2020
+@set VERSION 1.9
 
 @dircategory Data Compression
 @direntry
@@ -49,53 +49,54 @@ This manual is for Zutils (version @value{VERSION}, @value{UPDATED}).
 @end menu
 
 @sp 1
-Copyright @copyright{} 2009-2019 Antonio Diaz Diaz.
+Copyright @copyright{} 2009-2020 Antonio Diaz Diaz.
 
-This manual is free documentation: you have unlimited permission
-to copy, distribute and modify it.
+This manual is free documentation: you have unlimited permission to copy,
+distribute, and modify it.
 
 
 @node Introduction
 @chapter Introduction
 @cindex introduction
 
-Zutils is a collection of utilities able to process any combination of
-compressed and uncompressed files transparently. If any given file,
-including standard input, is compressed, its decompressed content is
-used. Compressed files are decompressed on the fly; no temporary files
-are created.
+@uref{http://www.nongnu.org/zutils/zutils.html,,Zutils}
+is a collection of utilities able to process any combination of
+compressed and uncompressed files transparently. If any file given,
+including standard input, is compressed, its decompressed content is used.
+Compressed files are decompressed on the fly; no temporary files are
+created.
 
 These utilities are not wrapper scripts but safer and more efficient C++
-programs. In particular the @samp{--recursive} option is very efficient
-in those utilities supporting it.
+programs. In particular the option @samp{--recursive} is very efficient in
+those utilities supporting it.
 
 @noindent
-The utilities provided are zcat, zcmp, zdiff, zgrep, ztest and zupdate.@*
-The formats supported are bzip2, gzip, lzip and xz.@*
-Zutils uses external compressors. The compressor to be used for each
-format is configurable at runtime.
-
-zcat, zcmp, zdiff, and zgrep are improved replacements for the shell
-scripts provided by GNU gzip. ztest is unique to zutils. zupdate is
-similar to gzip's znew.
-
-NOTE: Bzip2 and lzip provide well-defined values of exit status, which
-makes them safe to use with zutils. Gzip and xz may return ambiguous
-warning values, making them less reliable back ends for zutils.
+The utilities provided are zcat, zcmp, zdiff, zgrep, ztest, and zupdate.@*
+The formats supported are bzip2, gzip, lzip, and xz.@*
+Zutils uses external compressors. The compressor to be used for each format
+is configurable at runtime.
+
+zcat, zcmp, zdiff, and zgrep are improved replacements for the shell scripts
+provided by GNU gzip. ztest is unique to zutils. zupdate is similar to
+gzip's znew.
+
+NOTE: Bzip2 and lzip provide well-defined values of exit status, which makes
+them safe to use with zutils. Gzip and xz may return ambiguous warning
+values, making them less reliable back ends for zutils.
 @xref{compressor-requirements}.
 
-FORMAT NOTE 1: The @samp{--format} option allows the processing of a
-subset of formats in recursive mode and when trying compressed file
-names: @w{@samp{zgrep foo -r --format=bz2,lz somedir somefile.tar}}.
+FORMAT NOTE 1: The option @samp{--format} allows the processing of a subset
+of formats in recursive mode and when trying compressed file names:
+@w{@samp{zgrep foo -r --format=bz2,lz somedir somefile.tar}}.
 
-FORMAT NOTE 2: If the @samp{--force-format} option is given, the files
-are passed to the corresponding decompressor without verifying their
-format, allowing for example the processing of compress'd (.Z) files
-with gzip: @w{@samp{zcmp --force-format=gz file.Z file.lz}}.
+FORMAT NOTE 2: If the option @samp{--force-format} is given, the files are
+passed to the corresponding decompressor without verifying their format,
+allowing for example the processing of compress'd (.Z) files with gzip:
+@w{@samp{zcmp --force-format=gz file.Z file.lz}}.
 
-LANGUAGE NOTE: Uncompressed = not compressed = plain data; it may never
-have been compressed. Decompressed is used to refer to data which have
-undergone the process of decompression.
+LANGUAGE NOTE: Uncompressed = not compressed = plain data; it may never have
+been compressed. Decompressed is used to refer to data which have undergone
+the process of decompression.
 
 @sp 1
 Numbers given as arguments to options (positions, sizes) may be followed
@@ -120,9 +121,13 @@ Table of SI and binary prefixes (unit multipliers):
 @chapter Common options
 @cindex common options
 
-The following options are available in all the utilities. Rather than
-writing identical descriptions for each of the programs, they are
-described here.
+The following
+@uref{http://www.nongnu.org/arg-parser/manual/arg_parser_manual.html#Argument-syntax,,options}:
+are available in all the utilities. Rather than writing identical
+descriptions for each of the programs, they are described here.
+@ifnothtml
+@xref{Argument syntax,,,arg_parser}.
+@end ifnothtml
 
 @table @code
 @item -h
@@ -139,7 +144,7 @@ This version number should be included in all bug reports.
 @itemx --format=@var{format_list}
 Process only the formats listed in the comma-separated
 @var{format_list}. Valid formats are @samp{bz2}, @samp{gz}, @samp{lz},
-@samp{xz} and @samp{un} for @samp{uncompressed}, meaning "any file name
+@samp{xz}, and @samp{un} for @samp{uncompressed}, meaning "any file name
 without a known extension". This option excludes files based on
 extension, instead of format, because it is more efficient. The
 exclusion only applies to names generated automatically (for example
@@ -165,19 +170,22 @@ Don't read the runtime configuration file @samp{zutilsrc}.
 @itemx --gz=@var{command}
 @itemx --lz=@var{command}
 @itemx --xz=@var{command}
-Set program (may include arguments) to be used as (de)compressor for the
-given format. The name of the program can't begin with @samp{-}. These
-options override the values set in @file{zutilsrc}. The compression
-program used must meet three requirements:
+Set program to be used as (de)compressor for the corresponding format.
+@var{command} may include arguments. For example
+@w{@samp{--lz='plzip --threads=2'}}. The program set with @samp{--lz} is
+used for both compression and decompression. The other three are used only
+for decompression. The name of the program can't begin with @samp{-}. These
+options override the values set in @file{zutilsrc}. The compression program
+used must meet three requirements:
 
 @anchor{compressor-requirements}
 @enumerate
 @item
-When called with the @samp{-d} option, it must read compressed data from
+When called with the option @samp{-d}, it must read compressed data from
 the standard input and produce decompressed data on the standard output.
 @item
-If the @samp{-q} option is passed to zutils, the compression program
-must also accept it.
+If the option @samp{-q} is passed to zutils, the compression program must
+also accept it.
 @item
 It must return 0 if no errors occurred, and a non-zero value otherwise.
 @end enumerate
@@ -206,12 +214,12 @@ are further instructions in it):
 @item
 Any line beginning with @samp{#} is a comment line.
 @item
-Each non-comment line defines the command to be used for the given
+Each non-comment line defines the command to be used for the corresponding
 format, with the syntax:
 @example
 <format> = <compressor> [options]
 @end example
-where <format> is one of @samp{bz2}, @samp{gz}, @samp{lz} or @samp{xz}.
+where <format> is one of @samp{bz2}, @samp{gz}, @samp{lz}, or @samp{xz}.
 @end enumerate
 
 
@@ -219,20 +227,20 @@ where <format> is one of @samp{bz2}, @samp{gz}, @samp{lz} or @samp{xz}.
 @chapter Zcat
 @cindex zcat
 
-zcat copies each given file to standard output. If any given file is
-compressed, its decompressed content is used. If a given file does not
-exist, and its name does not end with one of the known extensions, zcat
-tries the compressed file names corresponding to the formats supported.
-If a file fails to decompress, zcat continues copying the rest of the
-files.
+zcat copies each @var{file} argument to standard output in sequence. If any
+file given is compressed, its decompressed content is copied. If a file
+given does not exist, and its name does not end with one of the known
+extensions, zcat tries the compressed file names corresponding to the
+formats supported. If a file fails to decompress, zcat continues copying the
+rest of the files.
 
 If a file is specified as @samp{-}, data are read from standard input,
 decompressed if needed, and sent to standard output. Data read from
 standard input must be of the same type; all uncompressed or all in the
-same compression format.
+same compressed format.
 
-If no files are specified, recursive searches examine the current
-working directory, and nonrecursive searches read standard input.
+If no files are specified, recursive searches examine the current working
+directory, and nonrecursive searches read standard input.
 
 The format for running zcat is:
 
@@ -241,7 +249,7 @@ zcat [@var{options}] [@var{files}]
 @end example
 
 @noindent
-Exit status is 0 if no errors occurred, non-zero otherwise.
+Exit status is 0 if no errors occurred, 1 otherwise.
 
 zcat supports the following options:
 
@@ -268,8 +276,8 @@ Number all output lines, starting with 1. The line count is unlimited.
 
 @item -O @var{format}
 @itemx --force-format=@var{format}
-Force the given compression format. Valid values for @var{format} are
-@samp{bz2}, @samp{gz}, @samp{lz} and @samp{xz}. If this option is used,
+Force the compressed format given. Valid values for @var{format} are
+@samp{bz2}, @samp{gz}, @samp{lz}, and @samp{xz}. If this option is used,
 the files are passed to the corresponding decompressor without verifying
 their format, and the exact file name must be given. Other names won't
 be tried.
@@ -280,14 +288,14 @@ Quiet operation. Suppress all messages.
 
 @item -r
 @itemx --recursive
-For each directory operand, read and process all files in that
-directory, recursively. Follow symbolic links in the command line, but
-skip symlinks that are encountered recursively.
+For each directory operand, read and process all files in that directory,
+recursively. Follow symbolic links given in the command line, but skip
+symbolic links that are encountered recursively.
 
 @item -R
 @itemx --dereference-recursive
-For each directory operand, read and process all files in that
-directory, recursively, following all symbolic links.
+For each directory operand, read and process all files in that directory,
+recursively, following all symbolic links.
 
 @item -s
 @itemx --squeeze-blank
@@ -316,11 +324,12 @@ Verbose mode. Show error messages.
 @chapter Zcmp
 @cindex zcmp
 
-zcmp compares two files (@samp{-} means standard input), and if they
-differ, tells the first byte and line number where they differ. Bytes
-and lines are numbered starting with 1. If any given file is compressed,
-its decompressed content is used. Compressed files are decompressed on
-the fly; no temporary files are created.
+zcmp compares two files and, if they differ, writes to standard output the
+first byte and line number where they differ. Bytes and lines are numbered
+starting with 1. A hyphen @samp{-} used as a @var{file} argument means
+standard input. If any file given is compressed, its decompressed content is
+used. Compressed files are decompressed on the fly; no temporary files are
+created.
 
 The format for running zcmp is:
 
@@ -329,10 +338,11 @@ zcmp [@var{options}] @var{file1} [@var{file2}]
 @end example
 
 @noindent
-This compares @var{file1} to @var{file2}. If @var{file2} is omitted zcmp
-tries the following:
+This compares @var{file1} to @var{file2}. The standard input is used only if
+@var{file1} or @var{file2} refers to standard input. If @var{file2} is
+omitted zcmp tries the following:
 
-@enumerate
+@itemize -
 @item
 If @var{file1} is compressed, compares its decompressed contents with
 the corresponding uncompressed file (the name of @var{file1} with the
@@ -340,10 +350,7 @@ extension removed).
 @item
 If @var{file1} is uncompressed, compares it with the decompressed
 contents of @var{file1}.[lz|bz2|gz|xz] (the first one that is found).
-@item
-If no suitable file is found, compares @var{file1} with data read from
-standard input.
-@end enumerate
+@end itemize
 
 @noindent
 An exit status of 0 means no differences were found, 1 means some
@@ -379,10 +386,10 @@ Compare at most @var{count} input bytes.
 
 @item -O [@var{format1}][,@var{format2}]
 @itemx --force-format=[@var{format1}][,@var{format2}]
-Force the given compression formats. Any of @var{format1} or
+Force the compressed formats given. Any of @var{format1} or
 @var{format2} may be omitted and the corresponding format will be
 automatically detected. Valid values for @var{format} are @samp{bz2},
-@samp{gz}, @samp{lz} and @samp{xz}. If at least one format is specified
+@samp{gz}, @samp{lz}, and @samp{xz}. If at least one format is specified
 with this option, the file is passed to the corresponding decompressor
 without verifying its format, and the exact file names of both
 @var{file1} and @var{file2} must be given. Other names won't be tried.
@@ -401,11 +408,12 @@ files differ.
 @chapter Zdiff
 @cindex zdiff
 
-zdiff compares two files (@samp{-} means standard input), and if they
-differ, shows the differences line by line. If any given file is
-compressed, its decompressed content is used. zdiff is a front end to
-the diff program and has the limitation that messages from diff refer to
-temporary file names instead of those specified.
+zdiff compares two files and, if they differ, writes to standard output the
+differences line by line. A hyphen @samp{-} used as a @var{file} argument
+means standard input. If any file given is compressed, its decompressed
+content is used. zdiff is a front end to the program diff and has the
+limitation that messages from diff refer to temporary file names instead of
+those specified.
 
 The format for running zdiff is:
 
@@ -414,10 +422,11 @@ zdiff [@var{options}] @var{file1} [@var{file2}]
 @end example
 
 @noindent
-This compares @var{file1} to @var{file2}. If @var{file2} is omitted
-zdiff tries the following:
+This compares @var{file1} to @var{file2}. The standard input is used only if
+@var{file1} or @var{file2} refers to standard input. If @var{file2} is
+omitted zdiff tries the following:
 
-@enumerate
+@itemize -
 @item
 If @var{file1} is compressed, compares its decompressed contents with
 the corresponding uncompressed file (the name of @var{file1} with the
@@ -425,10 +434,7 @@ extension removed).
 @item
 If @var{file1} is uncompressed, compares it with the decompressed
 contents of @var{file1}.[lz|bz2|gz|xz] (the first one that is found).
-@item
-If no suitable file is found, compares @var{file1} with data read from
-standard input.
-@end enumerate
+@end itemize
 
 @noindent
 An exit status of 0 means no differences were found, 1 means some
@@ -471,10 +477,10 @@ Ignore case differences in file contents.
 
 @item -O [@var{format1}][,@var{format2}]
 @itemx --force-format=[@var{format1}][,@var{format2}]
-Force the given compression formats. Any of @var{format1} or
+Force the compressed formats given. Any of @var{format1} or
 @var{format2} may be omitted and the corresponding format will be
 automatically detected. Valid values for @var{format} are @samp{bz2},
-@samp{gz}, @samp{lz} and @samp{xz}. If at least one format is specified
+@samp{gz}, @samp{lz}, and @samp{xz}. If at least one format is specified
 with this option, the file is passed to the corresponding decompressor
 without verifying its format, and the exact file names of both
 @var{file1} and @var{file2} must be given. Other names won't be tried.
@@ -517,9 +523,9 @@ Ignore all white space.
 @chapter Zgrep
 @cindex zgrep
 
-zgrep is a front end to the grep program that allows transparent search
-on any combination of compressed and uncompressed files. If any given
-file is compressed, its decompressed content is used. If a given file
+zgrep is a front end to the program grep that allows transparent search
+on any combination of compressed and uncompressed files. If any file
+given is compressed, its decompressed content is used. If a file given
 does not exist, and its name does not end with one of the known
 extensions, zgrep tries the compressed file names corresponding to the
 formats supported. If a file fails to decompress, zgrep continues
@@ -528,10 +534,10 @@ searching the rest of the files.
 If a file is specified as @samp{-}, data are read from standard input,
 decompressed if needed, and fed to grep. Data read from standard input
 must be of the same type; all uncompressed or all in the same
-compression format.
+compressed format.
 
-If no files are specified, recursive searches examine the current
-working directory, and nonrecursive searches read standard input.
+If no files are specified, recursive searches examine the current working
+directory, and nonrecursive searches read standard input.
 
 The format for running zgrep is:
 
@@ -572,7 +578,7 @@ Only print a count of matching lines per file.
 Print @var{n} lines of output context.
 
 @item --color[=@var{when}]
-Show matched strings in color. @var{when} is @samp{never}, @samp{always}
+Show matched strings in color. @var{when} is @samp{never}, @samp{always},
 or @samp{auto}.
 
 @item -e @var{pattern}
@@ -587,9 +593,9 @@ Treat @var{pattern} as an extended regular expression.
 @itemx --file=@var{file}
 Obtain patterns from @var{file}, one per line.@*
 When searching in several files at once, command substitution can be
-used with @code{-e} to read @var{file} only once, for example if
+used with @samp{-e} to read @var{file} only once, for example if
 @var{file} is not a regular file:
-@w{@code{zgrep -e "$(cat @var{file})" file1.lz file2.gz}}
+@w{@samp{zgrep -e "$(cat @var{file})" file1.lz file2.gz}}
 
 @item -F
 @itemx --fixed-strings
@@ -633,8 +639,8 @@ Show only the part of matching lines that actually matches @var{pattern}.
 
 @item -O @var{format}
 @itemx --force-format=@var{format}
-Force the given compression format. Valid values for @var{format} are
-@samp{bz2}, @samp{gz}, @samp{lz} and @samp{xz}. If this option is used,
+Force the compressed format given. Valid values for @var{format} are
+@samp{bz2}, @samp{gz}, @samp{lz}, and @samp{xz}. If this option is used,
 the files are passed to the corresponding decompressor without verifying
 their format, and the exact file name must be given. Other names won't
 be tried.
@@ -646,14 +652,14 @@ found, even if an error was detected.
 
 @item -r
 @itemx --recursive
-For each directory operand, read and process all files in that
-directory, recursively. Follow symbolic links in the command line, but
-skip symlinks that are encountered recursively.
+For each directory operand, read and process all files in that directory,
+recursively. Follow symbolic links given in the command line, but skip
+symbolic links that are encountered recursively.
 
 @item -R
 @itemx --dereference-recursive
-For each directory operand, read and process all files in that
-directory, recursively, following all symbolic links.
+For each directory operand, read and process all files in that directory,
+recursively, following all symbolic links.
 
 @item -s
 @itemx --no-messages
@@ -681,15 +687,17 @@ Match only whole lines.
 @chapter Ztest
 @cindex ztest
 
-ztest verifies the integrity of the specified compressed files.
+ztest verifies the integrity of the compressed files specified.
 Uncompressed files are ignored. If a file is specified as @samp{-}, the
 integrity of compressed data read from standard input is verified. Data
-read from standard input must be all in the same compression format. If
-a file fails to decompress, ztest continues verifying the rest of the
-files.
+read from standard input must be all in the same compressed format. If
+a file fails to decompress, does not exist, can't be opened, or is a
+terminal, ztest continues verifying the rest of the files. A final
+diagnostic is shown at verbosity level 1 or higher if any file fails the
+test when testing multiple files.
 
-If no files are specified, recursive searches examine the current
-working directory, and nonrecursive searches read standard input.
+If no files are specified, recursive searches examine the current working
+directory, and nonrecursive searches read standard input.
 
 Note that error detection in the xz format is broken. First, some xz
 files lack integrity information. Second, not all xz decompressors can
@@ -717,13 +725,12 @@ ztest supports the following options:
 @table @code
 @item -O @var{format}
 @itemx --force-format=@var{format}
-Force the given compression format. Valid values for @var{format} are
-@samp{bz2}, @samp{gz}, @samp{lz} and @samp{xz}. If this option is used,
-the files are passed to the corresponding decompressor without verifying
-their format, and any files in a format that the decompressor can't
-understand will fail. For example, @samp{--force-format=gz} can test
-gzipped (.gz) and compress'd (.Z) files if the compressor used is GNU
-gzip.
+Force the compressed format given. Valid values for @var{format} are
+@samp{bz2}, @samp{gz}, @samp{lz}, and @samp{xz}. If this option is used, the
+files are passed to the corresponding decompressor without verifying their
+format, and any files in a format that the decompressor can't understand
+will fail. For example, @samp{--force-format=gz} can test gzipped (.gz) and
+compress'd (.Z) files if the compressor used is GNU gzip.
 
 @item -q
 @itemx --quiet
@@ -731,14 +738,14 @@ Quiet operation. Suppress all messages.
 
 @item -r
 @itemx --recursive
-For each directory operand, read and process all files in that
-directory, recursively. Follow symbolic links in the command line, but
-skip symlinks that are encountered recursively.
+For each directory operand, read and process all files in that directory,
+recursively. Follow symbolic links given in the command line, but skip
+symbolic links that are encountered recursively.
 
 @item -R
 @itemx --dereference-recursive
-For each directory operand, read and process all files in that
-directory, recursively, following all symbolic links.
+For each directory operand, read and process all files in that directory,
+recursively, following all symbolic links.
 
 @item -v
 @itemx --verbose
@@ -752,40 +759,41 @@ Further -v's increase the verbosity level.
 @chapter Zupdate
 @cindex zupdate
 
-zupdate recompresses files from bzip2, gzip, and xz formats to lzip
-format. Each original is compared with the new file and then deleted.
-Only regular files with standard file name extensions are recompressed,
-other files are ignored. Compressed files are decompressed and then
-recompressed on the fly; no temporary files are created. If an error
-happens while recompressing a file, zupdate exits immediately without
-recompressing the rest of the files. The lzip format is chosen as
-destination because it is the most appropriate for long-term data
-archiving.
+zupdate recompresses files from bzip2, gzip, and xz formats to lzip format.
+Each original is compared with the new file and then deleted. Only regular
+files with standard file name extensions are recompressed, other files are
+ignored. Compressed files are decompressed and then recompressed on the fly;
+no temporary files are created. If an error happens while recompressing a
+file, zupdate exits immediately without recompressing the rest of the files.
+The lzip format is chosen as destination because it is the most appropriate
+for long-term data archiving.
 
-If no files are specified, recursive searches examine the current
-working directory, and nonrecursive searches do nothing.
+If no files are specified, recursive searches examine the current working
+directory, and nonrecursive searches do nothing.
 
 If the lzip compressed version of a file already exists, the file is
-skipped unless the @samp{--force} option is given. In this case, if the
+skipped unless the option @samp{--force} is given. In this case, if the
 comparison with the existing lzip version fails, an error is returned
 and the original file is not deleted. The operation of zupdate is meant
-to be safe and not produce any data loss. Therefore, existing lzip
+to be safe and not cause any data loss. Therefore, existing lzip
 compressed files are never overwritten nor deleted.
 
-Combining the @samp{--force} and @samp{--keep} options, as in
-@w{@code{zupdate -f -k *.gz}}, verifies that there are no differences
+Combining the options @samp{--force} and @samp{--keep}, as in
+@w{@samp{zupdate -f -k *.gz}}, verifies that there are no differences
 between each pair of files in a multiformat set of files.
 
-The names of the original files must have one of the following
-extensions: @samp{.bz2}, @samp{.tbz}, @samp{.tbz2}, @samp{.gz},
-@samp{.tgz}, @samp{.xz}, @samp{.txz}. The files produced have the
-extensions @samp{.lz} or @samp{.tar.lz}.
+The names of the original files must have one of the following extensions:@*
+@samp{.bz2}, @samp{.gz}, and @samp{.xz} are recompressed to @samp{.lz}.@*
+@samp{.tbz}, @samp{.tbz2}, @samp{.tgz}, and @samp{.txz} are recompressed to
+@samp{.tlz}.@*
+Keeping the combined extensions (@samp{.tgz} --> @samp{.tlz}) may be useful
+when recompressing Slackware packages, for example.
 
-Recompressing a file is much like copying or moving it; therefore
-zupdate preserves the access and modification dates, permissions, and,
-when possible, ownership of the file just as @samp{cp -p} does. (If the user
-ID or the group ID can't be duplicated, the file permission bits S_ISUID
-and S_ISGID are cleared).
+Recompressing a file is much like copying or moving it; therefore zupdate
+preserves the access and modification dates, permissions, and, when
+possible, ownership of the file just as @samp{cp -p} does. (If the user ID or
+the group ID can't be duplicated, the file permission bits S_ISUID and
+S_ISGID are cleared).
 
 The format for running zupdate is:
 
@@ -794,9 +802,8 @@ zupdate [@var{options}] [@var{files}]
 @end example
 
 @noindent
-Exit status is 0 if all the compressed files were successfully
-recompressed (if needed), compared and deleted (if requested). Non-zero
-otherwise.
+Exit status is 0 if all the compressed files were successfully recompressed
+(if needed), compared, and deleted (if requested). Non-zero otherwise.
 
 zupdate supports the following options:
 
@@ -814,8 +821,8 @@ Keep (don't delete) the input file after comparing it with the lzip file.
 
 @item -l
 @itemx --lzip-verbose
-Pass a @samp{-v} option to the lzip compressor so that it shows the
-compression ratio for each file processed. Using lzip 1.15 and newer, a
+Pass one option @samp{-v} to the lzip compressor so that it shows the
+compression ratio for each file processed. Using lzip 1.15 or newer, a
 second @samp{-l} shows the progress of compression. Use it together with
 @samp{-v} to see the name of the file.
 
@@ -825,14 +832,14 @@ Quiet operation. Suppress all messages.
 
 @item -r
 @itemx --recursive
-For each directory operand, read and process all files in that
-directory, recursively. Follow symbolic links in the command line, but
-skip symlinks that are encountered recursively.
+For each directory operand, read and process all files in that directory,
+recursively. Follow symbolic links given in the command line, but skip
+symbolic links that are encountered recursively.
 
 @item -R
 @itemx --dereference-recursive
-For each directory operand, read and process all files in that
-directory, recursively, following all symbolic links.
+For each directory operand, read and process all files in that directory,
+recursively, following all symbolic links.
 
 @item -v
 @itemx --verbose
@@ -840,8 +847,9 @@ Verbose mode. Show the files being processed. A second @samp{-v} also
 shows the files being ignored.
 
 @item -0 .. -9
-Set the compression level of lzip. By default zupdate passes @samp{-9}
-to lzip.
+Set the compression level of lzip. By default zupdate passes @samp{-9} to
+lzip. Custom compression options can be passed to lzip with the option
+@samp{--lz}. For example @w{@samp{--lz='lzip -9 -s64MiB'}}.
 
 @end table
 
@@ -858,7 +866,7 @@ for all eternity, if not longer.
 
 If you find a bug in zutils, please send electronic mail to
 @email{zutils-bug@@nongnu.org}. Include the version number, which you can
-find by running @w{@code{zupdate --version}}.
+find by running @w{@samp{zupdate --version}}.
 
 
 @node Concept index
diff --git a/rc.cc b/rc.cc
index 308cf0c..7ad51f4 100644
--- a/rc.cc
+++ b/rc.cc
@@ -1,18 +1,18 @@
-/*  Zutils - Utilities dealing with compressed files
-    Copyright (C) 2009-2019 Antonio Diaz Diaz.
+/* Zutils - Utilities dealing with compressed files
+   Copyright (C) 2009-2020 Antonio Diaz Diaz.
 
-    This program is free software: you can redistribute it and/or modify
-    it under the terms of the GNU General Public License as published by
-    the Free Software Foundation, either version 2 of the License, or
-    (at your option) any later version.
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 2 of the License, or
+   (at your option) any later version.
 
-    This program is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-    GNU General Public License for more details.
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
 
-    You should have received a copy of the GNU General Public License
-    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
 #define _FILE_OFFSET_BITS 64
@@ -37,12 +37,12 @@ int verbosity = 0;
 namespace {
 
 const char * const config_file_name = "zutilsrc";
-const char * const     program_year = "2019";
+const char * const     program_year = "2020";
 
 std::string compressor_names[num_formats] =
   { "bzip2", "gzip", "lzip", "xz" };		// default compressor names
 
-// args to compressors, maybe empty
+// args to compressors read from rc or from options --[bglx]z, maybe empty
 std::vector< std::string > compressor_args[num_formats];
 
 // vector of enabled formats plus [num_formats] for uncompressed.
@@ -93,10 +93,10 @@ bool trailing_escape( const std::string & s )
   }
 
 
-// Read a line discarding comments, leading whitespace and blank lines.
-// Escaped newlines are discarded.
-// Returns the empty string if at EOF.
-//
+/* Read a line discarding comments, leading whitespace, and blank lines.
+   Escaped newlines are discarded.
+   Returns the empty string if at EOF.
+*/
 const std::string & my_fgets( FILE * const f, int & linenum )
   {
   static std::string s;
@@ -237,7 +237,7 @@ void parse_format_list( const std::string & arg )
     enabled_formats[format_index] = true;
     }
   if( error )
-    { show_error( "Bad argument for '--format' option." ); std::exit( 1 ); }
+    { show_error( "Bad argument for option '--format'." ); std::exit( 1 ); }
   }
 
 
@@ -246,7 +246,7 @@ int parse_format_type( const std::string & arg )
   for( int i = 0; i < num_formats; ++i )
     if( arg == format_names[i] )
       return i;
-  show_error( "Bad argument for '--force-format' option." );
+  show_error( "Bad argument for option '--force-format'." );
   std::exit( 1 );
   }
 
diff --git a/rc.h b/rc.h
index 2a059bc..db04bcd 100644
--- a/rc.h
+++ b/rc.h
@@ -1,21 +1,21 @@
-/*  Zutils - Utilities dealing with compressed files
-    Copyright (C) 2009-2019 Antonio Diaz Diaz.
+/* Zutils - Utilities dealing with compressed files
+   Copyright (C) 2009-2020 Antonio Diaz Diaz.
 
-    This program is free software: you can redistribute it and/or modify
-    it under the terms of the GNU General Public License as published by
-    the Free Software Foundation, either version 2 of the License, or
-    (at your option) any later version.
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 2 of the License, or
+   (at your option) any later version.
 
-    This program is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-    GNU General Public License for more details.
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
 
-    You should have received a copy of the GNU General Public License
-    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-enum { fmt_bz2, fmt_gz, fmt_lz, fmt_xz, num_formats };
+enum { fmt_bz2, fmt_gz, fmt_lz, fmt_xz, num_formats };	// format_index
 const char * const format_names[num_formats] = { "bz2", "gz", "lz", "xz" };
 const char * const simple_extensions[num_formats] =
   { ".bz2", ".gz", ".lz", ".xz" };
diff --git a/recursive.cc b/recursive.cc
index 2f347f9..1b77a28 100644
--- a/recursive.cc
+++ b/recursive.cc
@@ -1,22 +1,22 @@
-/*  Zutils - Utilities dealing with compressed files
-    Copyright (C) 2009-2019 Antonio Diaz Diaz.
+/* Zutils - Utilities dealing with compressed files
+   Copyright (C) 2009-2020 Antonio Diaz Diaz.
 
-    This program is free software: you can redistribute it and/or modify
-    it under the terms of the GNU General Public License as published by
-    the Free Software Foundation, either version 2 of the License, or
-    (at your option) any later version.
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 2 of the License, or
+   (at your option) any later version.
 
-    This program is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-    GNU General Public License for more details.
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
 
-    You should have received a copy of the GNU General Public License
-    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-// Returns true if full_name is a regular file with an enabled extension
-// or (a link to) a directory.
+/* Returns true if full_name is a regular file with an enabled extension
+   or (a link to) a directory. */
 bool test_full_name( const std::string & full_name, const struct stat * stp,
                      const bool follow )
   {
@@ -41,12 +41,14 @@ bool test_full_name( const std::string & full_name, const struct stat * stp,
         { loop = true; break; }
       }
   if( loop )			// full_name already visited or above tree
-    show_file_error( full_name.c_str(), "warning: Recursive directory loop" );
+    show_file_error( full_name.c_str(), "warning: Recursive directory loop." );
   return !loop;			// (link to) directory
   }
 
 
-// Returns in input_filename the next filename.
+/* Returns in input_filename the next filename, or "." for stdin.
+   ("." was chosen because it is not a valid filename).
+   Sets 'error' to true if a directory fails to open. */
 bool next_filename( std::list< std::string > & filenames,
                     std::string & input_filename, bool & error,
                     const int recursive, const bool ignore_stdin = false,
@@ -56,10 +58,10 @@ bool next_filename( std::list< std::string > & filenames,
     {
     input_filename = filenames.front();
     filenames.pop_front();
-    if( input_filename.empty() || input_filename == "-" )
+    if( input_filename == "-" )
       {
       if( ignore_stdin ) continue;
-      input_filename.clear(); return true;
+      input_filename = "."; return true;
       }
     struct stat st;
     if( stat( input_filename.c_str(), &st ) == 0 && S_ISDIR( st.st_mode ) )
diff --git a/testsuite/check.sh b/testsuite/check.sh
index 8c0e64e..27b1a51 100755
--- a/testsuite/check.sh
+++ b/testsuite/check.sh
@@ -1,9 +1,9 @@
 #! /bin/sh
 # check script for Zutils - Utilities dealing with compressed files
-# Copyright (C) 2009-2019 Antonio Diaz Diaz.
+# Copyright (C) 2009-2020 Antonio Diaz Diaz.
 #
 # This script is free software: you have unlimited permission
-# to copy, distribute and modify it.
+# to copy, distribute, and modify it.
 
 LC_ALL=C
 export LC_ALL
@@ -74,6 +74,10 @@ for i in ${extensions}; do
 		test_failed $LINENO $i
 done
 
+printf "LZIP\001-.............................." | "${ZCAT}" -N > /dev/null 2>&1
+[ $? = 1 ] || test_failed $LINENO
+printf "LZIPxxxxxx" | "${ZCAT}" -N > /dev/null || test_failed $LINENO
+printf "BZh9xxxxxx" | "${ZCAT}" -N > /dev/null || test_failed $LINENO
 "${ZCAT}" -N -v -s "${testdir}"/zcat_vs.dat > /dev/null || test_failed $LINENO
 "${ZCAT}" -N < in > copy || test_failed $LINENO
 cmp in copy || test_failed $LINENO
@@ -91,6 +95,8 @@ cmp in copy || test_failed $LINENO
 cmp in copy || test_failed $LINENO
 "${ZCAT}" -N lz_only > copy || test_failed $LINENO
 cmp in copy || test_failed $LINENO
+cat in.lz in in in in | "${ZCAT}" -N > copy || test_failed $LINENO	# tdata
+cmp in copy || test_failed $LINENO
 "${ZCAT}" -N in in.gz in.bz2 in.lz -- -in- -in-.lz > copy || test_failed $LINENO
 cmp in6 copy || test_failed $LINENO
 "${ZCAT}" -Nq in in.gz in.bz2 in.lz "${bad0_lz}" -- -in- -in-.lz > copy
@@ -105,6 +111,8 @@ cmp in6 copy || test_failed $LINENO
 "${ZCAT}" -N -R . > /dev/null || test_failed $LINENO
 "${ZCAT}" -N -R > /dev/null || test_failed $LINENO
 
+"${ZCAT}" -Nq "" < in.lz > /dev/null
+[ $? = 1 ] || test_failed $LINENO
 "${ZCAT}" -Nq --format=, in.lz
 [ $? = 1 ] || test_failed $LINENO
 "${ZCAT}" -Nq --format=,lz in.lz
@@ -132,11 +140,11 @@ printf "\ntesting    zcmp-%s..." "$2"
 for i in ${extensions}; do
 	"${ZCMP}" -N in.$i || test_failed $LINENO $i
 	"${ZCMP}" -N in in.$i || test_failed $LINENO $i
-	"${ZCMP}" -N -i 1kB:1000 -n 500 in6 in.$i || test_failed $LINENO $i
 	"${ZCMP}" -N in in.$i --force-format=,$i || test_failed $LINENO $i
 	"${ZCMP}" -N in.$i in || test_failed $LINENO $i
-	"${ZCMP}" -N -i 1KiB:1024 -n 50 in.$i in6 || test_failed $LINENO $i
 	"${ZCMP}" -N in.$i in --force-format=$i || test_failed $LINENO $i
+	"${ZCMP}" -N -i 1kB:1000 -n 500 in6 in.$i || test_failed $LINENO $i
+	"${ZCMP}" -N -i 1KiB:1024 -n 50 in.$i in6 || test_failed $LINENO $i
 done
 
 "${ZCMP}" -Nq in in6
@@ -153,9 +161,13 @@ done
 "${ZCMP}" -N -i 0:11 -n 100 in.tar pin.tar || test_failed $LINENO
 "${ZCMP}" -N -i 0:11 -n 1Ki in.tar pin.tar || test_failed $LINENO
 "${ZCMP}" -N -i 0:11 -n 10KiB in.tar pin.tar || test_failed $LINENO
-"${ZCMP}" -N - || test_failed $LINENO
+"${ZCMP}" -N - - || test_failed $LINENO
+"${ZCMP}" -Nq -
+[ $? = 2 ] || test_failed $LINENO
 "${ZCMP}" -N in in || test_failed $LINENO
 "${ZCMP}" -N in || test_failed $LINENO
+"${ZCMP}" -N --format=gz,bz2 in || test_failed $LINENO
+"${ZCMP}" -N --format=gz in || test_failed $LINENO
 "${ZCMP}" -N in.lz in.gz || test_failed $LINENO
 "${ZCMP}" -N --lz='lzip -q' in.lz in.gz || test_failed $LINENO
 "${ZCMP}" -N in.gz -- -in-.lz || test_failed $LINENO
@@ -166,12 +178,16 @@ done
 "${ZCMP}" -N -- -in-.lz in || test_failed $LINENO
 "${ZCMP}" -N -- -in- in || test_failed $LINENO
 "${ZCMP}" -N in -- -in- || test_failed $LINENO
-"${ZCMP}" -N lz_only.lz < in || test_failed $LINENO
 "${ZCMP}" -N in.lz - < in || test_failed $LINENO
 "${ZCMP}" -N - in.lz < in || test_failed $LINENO
 "${ZCMP}" -N in - < in.lz || test_failed $LINENO
 "${ZCMP}" -N - in < in.lz || test_failed $LINENO
-"${ZCMP}" -N -q --force-format=lz in.lz
+"${ZCMP}" -N lz_only.lz - < in || test_failed $LINENO
+"${ZCMP}" -Nq lz_only.lz
+[ $? = 2 ] || test_failed $LINENO
+"${ZCMP}" -Nq "" in
+[ $? = 2 ] || test_failed $LINENO
+"${ZCMP}" -Nq --force-format=lz in.lz
 [ $? = 2 ] || test_failed $LINENO
 "${ZCMP}" -Nq --force-format=lz in.gz in.lz
 r=$?
@@ -184,7 +200,7 @@ r=$?
 [ $? = 2 ] || test_failed $LINENO
 "${ZCMP}" -Nq -n -1 in in
 [ $? = 2 ] || test_failed $LINENO
-"${ZCMP}" -Nq -n 100BB in in
+"${ZCMP}" -N -q -n 100BB in in
 [ $? = 2 ] || test_failed $LINENO
 "${ZCMP}" -N --bad-option in in 2> /dev/null
 [ $? = 2 ] || test_failed $LINENO
@@ -195,16 +211,20 @@ printf "\ntesting   zdiff-%s..." "$2"
 for i in ${extensions}; do
 	"${ZDIFF}" -N in.$i > /dev/null || test_failed $LINENO $i
 	"${ZDIFF}" -N in in.$i > /dev/null || test_failed $LINENO $i
-	"${ZDIFF}" -N --force-format=,$i in in.$i > /dev/null ||
+	"${ZDIFF}" -N in in.$i --force-format=,$i > /dev/null ||
 		test_failed $LINENO $i
 	"${ZDIFF}" -N in.$i in > /dev/null || test_failed $LINENO $i
-	"${ZDIFF}" -N --force-format=$i, in.$i in > /dev/null ||
+	"${ZDIFF}" -N in.$i in --force-format=$i, > /dev/null ||
 		test_failed $LINENO $i
 done
 
-"${ZDIFF}" -N in in6 > /dev/null && test_failed $LINENO
+"${ZDIFF}" -N in in6 > /dev/null
+[ $? = 1 ] || test_failed $LINENO
+# GNU diff 3.0 returns 2 when binary files differ
 "${ZDIFF}" -N in.tar pin.tar > /dev/null && test_failed $LINENO
-"${ZDIFF}" -N - || test_failed $LINENO
+"${ZDIFF}" -N - - || test_failed $LINENO
+"${ZDIFF}" -N - 2> /dev/null
+[ $? = 2 ] || test_failed $LINENO
 "${ZDIFF}" -N in in || test_failed $LINENO
 "${ZDIFF}" -N in || test_failed $LINENO
 "${ZDIFF}" -N --format=gz,bz2 in || test_failed $LINENO
@@ -219,14 +239,18 @@ done
 "${ZDIFF}" -N -- -in-.lz in > /dev/null || test_failed $LINENO
 "${ZDIFF}" -N -- -in- in > /dev/null || test_failed $LINENO
 "${ZDIFF}" -N in -- -in- > /dev/null || test_failed $LINENO
-"${ZDIFF}" -N lz_only.lz < in > /dev/null || test_failed $LINENO
 "${ZDIFF}" -N in.lz - < in > /dev/null || test_failed $LINENO
 "${ZDIFF}" -N - in.lz < in > /dev/null || test_failed $LINENO
 "${ZDIFF}" -N in - < in.lz > /dev/null || test_failed $LINENO
 "${ZDIFF}" -N - in < in.lz > /dev/null || test_failed $LINENO
+"${ZDIFF}" -N lz_only.lz - < in > /dev/null || test_failed $LINENO
+"${ZDIFF}" -N lz_only.lz 2> /dev/null
+[ $? = 2 ] || test_failed $LINENO
+"${ZDIFF}" -N "" in 2> /dev/null
+[ $? = 2 ] || test_failed $LINENO
 "${ZDIFF}" -N --bz2='-bzip2' in.bz2 2> /dev/null
 [ $? = 2 ] || test_failed $LINENO
-"${ZDIFF}" -N -q --force-format=bz2 in.bz2 2> /dev/null
+"${ZDIFF}" -Nq --force-format=bz2 in.bz2 2> /dev/null
 [ $? = 2 ] || test_failed $LINENO
 "${ZDIFF}" -N -q --force-format=,lz in.lz in.bz2 > /dev/null 2>&1
 r=$?
@@ -237,14 +261,14 @@ r=$?
 mkdir tmp2
 cat in > tmp2/a || framework_failure
 cat in.lz > tmp2/a.lz || framework_failure
-"${ZDIFF}" -N --format=bz2 tmp2/a < /dev/null > /dev/null
-[ $? = 1 ] || test_failed $LINENO
-"${ZDIFF}" -N --format=gz tmp2/a < /dev/null > /dev/null
-[ $? = 1 ] || test_failed $LINENO
-"${ZDIFF}" -N --format=lz tmp2/a.lz < /dev/null > /dev/null
-[ $? = 1 ] || test_failed $LINENO
-"${ZDIFF}" -N --format=lz tmp2/a < /dev/null || test_failed $LINENO
-"${ZDIFF}" -N --format=un tmp2/a.lz < /dev/null || test_failed $LINENO
+"${ZDIFF}" -N --format=bz2 tmp2/a 2> /dev/null
+[ $? = 2 ] || test_failed $LINENO
+"${ZDIFF}" -N --format=gz tmp2/a 2> /dev/null
+[ $? = 2 ] || test_failed $LINENO
+"${ZDIFF}" -N --format=lz tmp2/a.lz 2> /dev/null
+[ $? = 2 ] || test_failed $LINENO
+"${ZDIFF}" -N --format=lz tmp2/a || test_failed $LINENO
+"${ZDIFF}" -N --format=un tmp2/a.lz || test_failed $LINENO
 rm -r tmp2 || framework_failure
 
 
@@ -300,6 +324,8 @@ done
 
 "${ZGREP}" -N "GNU" .
 [ $? = 1 ] || test_failed $LINENO
+"${ZGREP}" -N "GNU" "" < in.lz 2> /dev/null
+[ $? = 2 ] || test_failed $LINENO
 "${ZGREP}" -N --bad-option 2> /dev/null
 [ $? = 2 ] || test_failed $LINENO
 "${ZGREP}" -N "GNU" -s nx_file
@@ -336,11 +362,13 @@ done
 "${ZTEST}" -Nq in.gz "${bad0_lz}" in.bz2 "${bad1_lz}" in.lz
 [ $? = 2 ] || test_failed $LINENO
 lines=`"${ZTEST}" -N in.gz "${bad0_lz}" in.bz2 "${bad1_lz}" in.lz 2>&1 | wc -l`
-[ "${lines}" -eq 2 ] || test_failed $LINENO
+[ "${lines}" -eq 2 ] || test_failed $LINENO "${lines}"
 lines=`"${ZTEST}" -Nv in.gz "${bad0_lz}" in.bz2 "${bad1_lz}" in.lz 2>&1 | wc -l`
-[ "${lines}" -eq 5 ] || test_failed $LINENO
+[ "${lines}" -eq 6 ] || test_failed $LINENO "${lines}"
 "${ZTEST}" -Nq < in
 [ $? = 2 ] || test_failed $LINENO
+"${ZTEST}" -Nq "" < in.lz
+[ $? = 1 ] || test_failed $LINENO
 dd if=in.lz bs=1000 count=1 2> /dev/null | "${ZTEST}" -N -q
 [ $? = 2 ] || test_failed $LINENO
 "${ZTEST}" -Nq --force-format=lz in.bz2
@@ -353,6 +381,7 @@ dd if=in.lz bs=1000 count=1 2> /dev/null | "${ZTEST}" -N -q
 
 printf "\ntesting zupdate-%s..." "$2"
 
+"${ZUPDATE}" -N "" || test_failed $LINENO
 cat in.bz2 > a.bz2 || framework_failure
 cat in.gz > a.gz || framework_failure
 "${ZUPDATE}" -Nq --bz2=bad_command a.bz2
@@ -415,6 +444,24 @@ cat in.gz > a.gz || framework_failure
 [ -e a.lz ] || test_failed $LINENO
 rm -f a.lz || framework_failure
 
+cat in.bz2 > a.tbz || framework_failure		# keep combined extensions
+cat in.bz2 > b.tbz2 || framework_failure
+cat in.gz > c.tgz || framework_failure
+"${ZUPDATE}" -N a.tbz b.tbz2 c.tgz || test_failed $LINENO
+[ ! -e a.tbz ] || test_failed $LINENO
+[ ! -e b.tbz2 ] || test_failed $LINENO
+[ ! -e c.tgz ] || test_failed $LINENO
+[ ! -e a ] || test_failed $LINENO
+[ ! -e b ] || test_failed $LINENO
+[ ! -e c ] || test_failed $LINENO
+[ ! -e a.lz ] || test_failed $LINENO
+[ ! -e b.lz ] || test_failed $LINENO
+[ ! -e c.lz ] || test_failed $LINENO
+[ -e a.tlz ] || test_failed $LINENO
+[ -e b.tlz ] || test_failed $LINENO
+[ -e c.tlz ] || test_failed $LINENO
+rm -f a.tlz b.tlz c.tlz || framework_failure
+
 cat in.bz2 > a.bz2 || framework_failure
 cat "${bad0_gz}" > b.gz || framework_failure
 cat in.gz > c.gz || framework_failure
@@ -434,6 +481,13 @@ cat in.bz2 > a.bz2 || framework_failure
 [ -e a.lz ] || test_failed $LINENO
 rm -f a.lz || framework_failure
 
+cat in.gz > 'name with spaces.gz' || framework_failure
+"${ZUPDATE}" -N -1 -q 'name with spaces.gz' || test_failed $LINENO
+[ ! -e 'name with spaces.gz' ] || test_failed $LINENO
+[ -e 'name with spaces.lz' ] || test_failed $LINENO
+"${ZCMP}" -N in 'name with spaces.lz' || test_failed $LINENO
+rm -f 'name with spaces.lz' || framework_failure
+
 mkdir tmp2
 mkdir tmp2/tmp3
 cat in.bz2 > tmp2/tmp3/a.bz2 || framework_failure
diff --git a/zcat.cc b/zcat.cc
index 5d400ad..f852c74 100644
--- a/zcat.cc
+++ b/zcat.cc
@@ -1,18 +1,18 @@
-/*  Zcat - decompress and concatenate files to standard output
-    Copyright (C) 2010-2019 Antonio Diaz Diaz.
+/* Zcat - decompress and concatenate files to standard output
+   Copyright (C) 2010-2020 Antonio Diaz Diaz.
 
-    This program is free software: you can redistribute it and/or modify
-    it under the terms of the GNU General Public License as published by
-    the Free Software Foundation, either version 2 of the License, or
-    (at your option) any later version.
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 2 of the License, or
+   (at your option) any later version.
 
-    This program is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-    GNU General Public License for more details.
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
 
-    You should have received a copy of the GNU General Public License
-    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
 #define _FILE_OFFSET_BITS 64
@@ -90,19 +90,21 @@ Line_number line_number;
 
 void show_help()
   {
-  std::printf( "Zcat copies each given file to standard output. If any given file is\n"
-               "compressed, its decompressed content is used. If a given file does not\n"
-               "exist, and its name does not end with one of the known extensions, zcat\n"
-               "tries the compressed file names corresponding to the formats supported.\n"
+  std::printf( "zcat copies each file argument to standard output in sequence. If any\n"
+               "file given is compressed, its decompressed content is copied. If a file\n"
+               "given does not exist, and its name does not end with one of the known\n"
+               "extensions, zcat tries the compressed file names corresponding to the\n"
+               "formats supported. If a file fails to decompress, zcat continues copying the\n"
+               "rest of the files.\n"
                "\nIf a file is specified as '-', data are read from standard input,\n"
                "decompressed if needed, and sent to standard output. Data read from\n"
                "standard input must be of the same type; all uncompressed or all in the\n"
-               "same compression format.\n"
+               "same compressed format.\n"
                "\nIf no files are specified, recursive searches examine the current\n"
                "working directory, and nonrecursive searches read standard input.\n"
-               "\nThe formats supported are bzip2, gzip, lzip and xz.\n"
+               "\nThe formats supported are bzip2, gzip, lzip, and xz.\n"
                "\nUsage: zcat [options] [files]\n"
-               "\nExit status is 0 if no errors occurred, non-zero otherwise.\n"
+               "\nExit status is 0 if no errors occurred, 1 otherwise.\n"
                "\nOptions:\n"
                "  -h, --help                   display this help and exit\n"
                "  -V, --version                output version information and exit\n"
@@ -113,7 +115,7 @@ void show_help()
                "  -M, --format=<list>          process only the formats in <list>\n"
                "  -n, --number                 number all output lines\n"
                "  -N, --no-rcfile              don't read runtime configuration file\n"
-               "  -O, --force-format=<fmt>     force given format (bz2, gz, lz, xz)\n"
+               "  -O, --force-format=<fmt>     force the format given (bz2, gz, lz, xz)\n"
                "  -q, --quiet                  suppress all messages\n"
                "  -r, --recursive              operate recursively on directories\n"
                "  -R, --dereference-recursive  recursively follow symbolic links\n"
@@ -130,10 +132,10 @@ void show_help()
   }
 
 
-int do_cat( const int infd, const int buffer_size,
-            uint8_t * const inbuf, uint8_t * const outbuf,
-            const std::string & input_filename,
-            const Cat_options & cat_options )
+bool do_cat( const int infd, const int buffer_size,
+             uint8_t * const inbuf, uint8_t * const outbuf,
+             const std::string & input_filename,
+             const Cat_options & cat_options )
   {
   static int at_bol = 1;	// at begin of line. 0 = false, 1 = true,
 				// 2 = at begin of second blank line.
@@ -148,7 +150,7 @@ int do_cat( const int infd, const int buffer_size,
       if( outpos >= buffer_size )
         {
         if( writeblock( STDOUT_FILENO, outbuf, outpos ) != outpos )
-          { show_error( "Write error", errno ); return 1; }
+          { show_error( "Write error", errno ); return false; }
         outpos = 0;
         }
       if( inpos > rd )			// inbuf is empty
@@ -157,14 +159,14 @@ int do_cat( const int infd, const int buffer_size,
         if( rd != buffer_size && errno )
           {
           show_file_error( input_filename.c_str(), "Read error", errno );
-          return 1;
+          return false;
           }
         if( rd == 0 )
           {
           if( writeblock( STDOUT_FILENO, outbuf, outpos ) != outpos )
-            { show_error( "Write error", errno ); return 1; }
+            { show_error( "Write error", errno ); return false; }
           outpos = 0;
-          return 0;
+          return true;
           }
         inpos = 0;
         inbuf[rd] = '\n';		// sentinel newline
@@ -226,32 +228,27 @@ int do_cat( const int infd, const int buffer_size,
   }
 
 
-int cat( int infd, const int format_index, const std::string & input_filename,
-         const Cat_options & cat_options )
+bool cat( int infd, const int format_index, const std::string & input_filename,
+          const Cat_options & cat_options )
   {
   enum { buffer_size = 4096, outbuf_size = (5 * buffer_size) + 256 + 1 };
-    // buffer with space for sentinel newline at the end
+    // input buffer with space for sentinel newline at the end
   uint8_t * const inbuf = new uint8_t[buffer_size+1];
-    // buffer with space for character quoting, 255-digit line number,
+    // output buffer with space for character quoting, 255-digit line number,
     // worst case flushing respect to inbuf, and a canary byte.
   uint8_t * const outbuf = new uint8_t[outbuf_size];
   outbuf[outbuf_size-1] = 0;
-  int retval = 0;
   Children children;
-  if( !set_data_feeder( input_filename, &infd, children, format_index ) )
-    retval = 1;
-  else
-    retval = do_cat( infd, buffer_size, inbuf, outbuf,
-                     input_filename, cat_options );
-
-  if( !good_status( children, retval == 0 ) ) retval = 1;
-
-  if( retval == 0 && close( infd ) != 0 )
-    { show_close_error(); retval = 1; }
-  if( outbuf[outbuf_size-1] != 0 )
-    internal_error( "buffer overflow." );
+  bool error = false;
+
+  if( !set_data_feeder( input_filename, &infd, children, format_index ) ||
+      !do_cat( infd, buffer_size, inbuf, outbuf, input_filename, cat_options ) )
+    error = true;
+  if( !good_status( children, !error ) ) error = true;
+  if( !error && close( infd ) != 0 ) { show_close_error(); error = true; }
+  if( outbuf[outbuf_size-1] != 0 ) internal_error( "buffer overflow." );
   delete[] outbuf; delete[] inbuf;
-  return retval;
+  return !error;
   }
 
 } // end namespace
@@ -264,8 +261,8 @@ int main( const int argc, const char * const argv[] )
   int recursive = 0;			// 1 = '-r', 2 = '-R'
   std::list< std::string > filenames;
   Cat_options cat_options;
-  invocation_name = argv[0];
   program_name = "zcat";
+  invocation_name = ( argc > 0 ) ? argv[0] : program_name;
 
   const Arg_parser::Option options[] =
     {
@@ -357,16 +354,15 @@ int main( const int argc, const char * const argv[] )
   if( filenames.empty() ) filenames.push_back( recursive ? "." : "-" );
 
   std::string input_filename;
-  int retval = 0;
   bool error = false;
   bool stdin_used = false;
   while( next_filename( filenames, input_filename, error, recursive ) )
     {
     int infd;
-    if( input_filename.empty() )
+    if( input_filename == "." )
       {
       if( stdin_used ) continue; else stdin_used = true;
-      infd = STDIN_FILENO;
+      infd = STDIN_FILENO; input_filename = "-";
       }
     else
       {
@@ -374,10 +370,11 @@ int main( const int argc, const char * const argv[] )
       if( infd < 0 ) { error = true; continue; }
       }
 
-    const int tmp = cat( infd, format_index, input_filename, cat_options );
-    if( tmp > retval ) retval = tmp;
+    if( !cat( infd, format_index, input_filename, cat_options ) ) error = true;
 
-    if( input_filename.size() ) close( infd );
+    if( close( infd ) != 0 )
+      { show_file_error( input_filename.c_str(), "Error closing input file",
+                         errno ); error = true; }
     }
 
   if( std::fclose( stdout ) != 0 )
@@ -385,6 +382,5 @@ int main( const int argc, const char * const argv[] )
     show_error( "Error closing stdout", errno );
     error = true;
     }
-  if( error && retval == 0 ) retval = 1;
-  return retval;
+  return error;
   }
diff --git a/zcatgrep.cc b/zcatgrep.cc
index 10bc1ea..0d16cb3 100644
--- a/zcatgrep.cc
+++ b/zcatgrep.cc
@@ -1,18 +1,18 @@
-/*  Common code for zcat and zgrep
-    Copyright (C) 2010-2019 Antonio Diaz Diaz.
+/* Common code for zcat and zgrep
+   Copyright (C) 2010-2020 Antonio Diaz Diaz.
 
-    This program is free software: you can redistribute it and/or modify
-    it under the terms of the GNU General Public License as published by
-    the Free Software Foundation, either version 2 of the License, or
-    (at your option) any later version.
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 2 of the License, or
+   (at your option) any later version.
 
-    This program is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-    GNU General Public License for more details.
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
 
-    You should have received a copy of the GNU General Public License
-    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
 #ifndef O_BINARY
diff --git a/zcmp.cc b/zcmp.cc
index 2408ca0..b97d5ef 100644
--- a/zcmp.cc
+++ b/zcmp.cc
@@ -1,18 +1,18 @@
-/*  Zcmp - decompress and compare two files byte by byte
-    Copyright (C) 2010-2019 Antonio Diaz Diaz.
+/* Zcmp - decompress and compare two files byte by byte
+   Copyright (C) 2010-2020 Antonio Diaz Diaz.
 
-    This program is free software: you can redistribute it and/or modify
-    it under the terms of the GNU General Public License as published by
-    the Free Software Foundation, either version 2 of the License, or
-    (at your option) any later version.
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 2 of the License, or
+   (at your option) any later version.
 
-    This program is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-    GNU General Public License for more details.
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
 
-    You should have received a copy of the GNU General Public License
-    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
 #define _FILE_OFFSET_BITS 64
@@ -50,22 +50,21 @@ namespace {
 
 void show_help()
   {
-  std::printf( "Zcmp compares two files ('-' means standard input), and if they differ,\n"
-               "tells the first byte and line number where they differ. Bytes and lines\n"
-               "are numbered starting with 1. If any given file is compressed, its\n"
-               "decompressed content is used. Compressed files are decompressed on the\n"
-               "fly; no temporary files are created.\n"
-               "\nThe formats supported are bzip2, gzip, lzip and xz.\n"
+  std::printf( "zcmp compares two files and, if they differ, writes to standard output the\n"
+               "first byte and line number where they differ. Bytes and lines are numbered\n"
+               "starting with 1. A hyphen '-' used as a file argument means standard input.\n"
+               "If any file given is compressed, its decompressed content is used. Compressed\n"
+               "files are decompressed on the fly; no temporary files are created.\n"
+               "\nThe formats supported are bzip2, gzip, lzip, and xz.\n"
                "\nUsage: zcmp [options] file1 [file2]\n"
-               "\nZcmp compares file1 to file2. If file2 is omitted zcmp tries the\n"
+               "\nzcmp compares file1 to file2. The standard input is used only if file1 or\n"
+               "file2 refers to standard input. If file2 is omitted zcmp tries the\n"
                "following:\n"
-               "\n  1. If file1 is compressed, compares its decompressed contents with\n"
+               "\n  - If file1 is compressed, compares its decompressed contents with\n"
                "  the corresponding uncompressed file (the name of file1 with the\n"
                "  extension removed).\n"
-               "\n  2. If file1 is uncompressed, compares it with the decompressed\n"
+               "\n  - If file1 is uncompressed, compares it with the decompressed\n"
                "  contents of file1.[lz|bz2|gz|xz] (the first one that is found).\n"
-               "\n  3. If no suitable file is found, compares file1 with data read from\n"
-               "  standard input.\n"
                "\nExit status is 0 if inputs are identical, 1 if different, 2 if trouble.\n"
                "\nOptions:\n"
                "  -h, --help                        display this help and exit\n"
@@ -76,7 +75,7 @@ void show_help()
                "  -M, --format=<list>               process only the formats in <list>\n"
                "  -n, --bytes=<n>                   compare at most <n> bytes\n"
                "  -N, --no-rcfile                   don't read runtime configuration file\n"
-               "  -O, --force-format=[<f1>][,<f2>]  force given formats (bz2, gz, lz, xz)\n"
+               "  -O, --force-format=[<f1>][,<f2>]  force the formats given (bz2, gz, lz, xz)\n"
                "  -q, --quiet                       suppress all messages\n"
                "  -s, --silent                      (same as --quiet)\n"
                "  -v, --verbose                     verbose mode (same as --list)\n"
@@ -84,7 +83,7 @@ void show_help()
                "      --gz=<command>                set compressor and options for gzip format\n"
                "      --lz=<command>                set compressor and options for lzip format\n"
                "      --xz=<command>                set compressor and options for xz format\n"
-               "Numbers may be followed by a multiplier: k = kB = 10^3 = 1000,\n"
+               "\nNumbers may be followed by a multiplier: k = kB = 10^3 = 1000,\n"
                "Ki = KiB = 2^10 = 1024, M = 10^6, Mi = 2^20, G = 10^9, Gi = 2^30, etc...\n" );
   show_help_addr();
   }
@@ -326,8 +325,8 @@ int main( const int argc, const char * const argv[] )
   long long max_size = -1;			// < 0 means unlimited size
   int format_types[2] = { -1, -1 };
   bool print_bytes = false;
-  invocation_name = argv[0];
   program_name = "zcmp";
+  invocation_name = ( argc > 0 ) ? argv[0] : program_name;
 
   const Arg_parser::Option options[] =
     {
@@ -403,28 +402,33 @@ int main( const int argc, const char * const argv[] )
     STDIN_FILENO : open_instream( filenames[0] );
   if( infd[0] < 0 ) return 2;
 
-  if( ( files == 1 && filenames[0] == "-" ) ||
-      ( files == 2 && check_identical( filenames[0].c_str(),
-                                       filenames[1].c_str() ) ) )
-    {
-    if( ignore_initial[0] == ignore_initial[1] ) return 0;
-    else { show_error( "Can't compare parts of same file." ); return 2; }
-    }
-
   if( files == 2 )
     {
+    if( check_identical( filenames[0].c_str(), filenames[1].c_str() ) )
+      {
+      if( ignore_initial[0] == ignore_initial[1] ) return 0;
+      else { show_error( "Can't compare parts of same file." ); return 2; }
+      }
     infd[1] = ( filenames[1] == "-" ) ?
       STDIN_FILENO : open_instream( filenames[1] );
     if( infd[1] < 0 ) return 2;
     }
   else
     {
+    if( filenames[0] == "-" )
+      { show_error( "Missing operand after '-'.", 0, true ); return 2; }
     if( format_types[0] >= 0 || format_types[1] >= 0 )
       { show_error( "Two files must be given when format is specified.", 0, true );
         return 2; }
     filenames[1] = filenames[0];
     infd[1] = open_other_instream( filenames[1] );
-    if( infd[1] < 0 ) { infd[1] = STDIN_FILENO; filenames[1] = "-"; }
+    if( infd[1] < 0 )
+      {
+      if( verbosity >= 0 )
+        std::fprintf( stderr, "%s: Can't find file to compare with '%s'.\n",
+                      program_name, filenames[0].c_str() );
+      show_error( 0, 0, true ); return 2;
+      }
     }
 
   int old_infd[2];		// copy of file descriptors of the two files
diff --git a/zcmpdiff.cc b/zcmpdiff.cc
index c779251..153b232 100644
--- a/zcmpdiff.cc
+++ b/zcmpdiff.cc
@@ -1,18 +1,18 @@
-/*  Common code for zcmp and zdiff
-    Copyright (C) 2010-2019 Antonio Diaz Diaz.
+/* Common code for zcmp and zdiff
+   Copyright (C) 2010-2020 Antonio Diaz Diaz.
 
-    This program is free software: you can redistribute it and/or modify
-    it under the terms of the GNU General Public License as published by
-    the Free Software Foundation, either version 2 of the License, or
-    (at your option) any later version.
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 2 of the License, or
+   (at your option) any later version.
 
-    This program is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-    GNU General Public License for more details.
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
 
-    You should have received a copy of the GNU General Public License
-    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
 #ifndef O_BINARY
@@ -38,10 +38,10 @@ int open_other_instream( std::string & name )
     name += extension_to( eindex );
     return open( name.c_str(), O_RDONLY | O_BINARY );
     }
-  if( eindex < 0 )
+  if( eindex < 0 )			// search compressed version
     for( int i = 0; i < num_formats; ++i )
       if( enabled_format( format_order[i] ) )
-        {				// search compressed version
+        {
         const std::string s( name + simple_extensions[format_order[i]] );
         const int infd = open( s.c_str(), O_RDONLY | O_BINARY );
         if( infd >= 0 ) { name = s; return infd; }
@@ -63,7 +63,7 @@ void parse_format_types2( const std::string & arg, int format_types[2] )
 
 bool check_identical( const char * const name1, const char * const name2 )
   {
-  if( !std::strcmp( name1, name2 ) ) return true;
+  if( std::strcmp( name1, name2 ) == 0 ) return true;
   struct stat stat1, stat2;
   if( stat( name1, &stat1 ) || stat( name2, &stat2 ) ) return false;
   return ( stat1.st_ino == stat2.st_ino && stat1.st_dev == stat2.st_dev );
diff --git a/zdiff.cc b/zdiff.cc
index b9106c7..9312253 100644
--- a/zdiff.cc
+++ b/zdiff.cc
@@ -1,18 +1,18 @@
-/*  Zdiff - decompress and compare two files line by line
-    Copyright (C) 2010-2019 Antonio Diaz Diaz.
+/* Zdiff - decompress and compare two files line by line
+   Copyright (C) 2010-2020 Antonio Diaz Diaz.
 
-    This program is free software: you can redistribute it and/or modify
-    it under the terms of the GNU General Public License as published by
-    the Free Software Foundation, either version 2 of the License, or
-    (at your option) any later version.
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 2 of the License, or
+   (at your option) any later version.
 
-    This program is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-    GNU General Public License for more details.
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
 
-    You should have received a copy of the GNU General Public License
-    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
 #define _FILE_OFFSET_BITS 64
@@ -39,6 +39,7 @@
 #include "rc.h"
 #include "zutils.h"
 
+// 'verbosity' is always 0 in zdiff; no --verbose or --quiet available.
 
 namespace {
 
@@ -48,23 +49,23 @@ std::string fifonames[2];	// names of the two fifos passed to diff
 
 void show_help()
   {
-  std::printf( "Zdiff compares two files ('-' means standard input), and if they\n"
-               "differ, shows the differences line by line. If any given file is\n"
-               "compressed, its decompressed content is used. Zdiff is a front end to\n"
-               "the diff program and has the limitation that messages from diff refer to\n"
-               "temporary filenames instead of those specified.\n"
-               "\nThe formats supported are bzip2, gzip, lzip and xz.\n"
+  std::printf( "zdiff compares two files and, if they differ, writes to standard output the\n"
+               "differences line by line. A hyphen '-' used as a file argument means standard\n"
+               "input. If any file given is compressed, its decompressed content is used.\n"
+               "zdiff is a front end to the program diff and has the limitation that messages\n"
+               "from diff refer to temporary file names instead of those specified.\n"
+               "\nThe formats supported are bzip2, gzip, lzip, and xz.\n"
                "\nUsage: zdiff [options] file1 [file2]\n"
-               "\nZdiff compares file1 to file2. If file2 is omitted zdiff tries the\n"
+               "\nzdiff compares file1 to file2. The standard input is used only if file1 or\n"
+               "file2 refers to standard input. If file2 is omitted zdiff tries the\n"
                "following:\n"
-               "\n  1. If file1 is compressed, compares its decompressed contents with\n"
+               "\n  - If file1 is compressed, compares its decompressed contents with\n"
                "  the corresponding uncompressed file (the name of file1 with the\n"
                "  extension removed).\n"
-               "\n  2. If file1 is uncompressed, compares it with the decompressed\n"
+               "\n  - If file1 is uncompressed, compares it with the decompressed\n"
                "  contents of file1.[lz|bz2|gz|xz] (the first one that is found).\n"
-               "\n  3. If no suitable file is found, compares file1 with data read from\n"
-               "  standard input.\n"
                "\nExit status is 0 if inputs are identical, 1 if different, 2 if trouble.\n"
+               "Some options only work if the diff program used supports them.\n"
                "\nOptions:\n"
                "  -h, --help                        display this help and exit\n"
                "  -V, --version                     output version information and exit\n"
@@ -78,7 +79,7 @@ void show_help()
                "  -i, --ignore-case                 ignore case differences in file contents\n"
                "  -M, --format=<list>               process only the formats in <list>\n"
                "  -N, --no-rcfile                   don't read runtime configuration file\n"
-               "  -O, --force-format=[<f1>][,<f2>]  force given formats (bz2, gz, lz, xz)\n"
+               "  -O, --force-format=[<f1>][,<f2>]  force the formats given (bz2, gz, lz, xz)\n"
                "  -p, --show-c-function             show which C function each change is in\n"
                "  -q, --brief                       output only whether files differ\n"
                "  -s, --report-identical-files      report when two files are identical\n"
@@ -87,6 +88,8 @@ void show_help()
                "  -u                                use the unified output format\n"
                "  -U, --unified=<n>                 same as -u but use <n> lines of context\n"
                "  -w, --ignore-all-space            ignore all white space\n"
+               "  -W, --width=<n>                   output at most <n> print columns\n"
+               "  -y, --side-by-side                output in two columns\n"
                "      --bz2=<command>               set compressor and options for bzip2 format\n"
                "      --gz=<command>                set compressor and options for gzip format\n"
                "      --lz=<command>                set compressor and options for lzip format\n"
@@ -112,8 +115,8 @@ extern "C" void remove_fifos()
   }
 
 
-// Set fifonames[i] to "${TMPDIR}/<coded_pid>[_-]<basename(filenames[i])>"
-// and create FIFOs.
+/* Set fifonames[i] to "${TMPDIR}/<coded_pid>[_-]<basename(filenames[i])>"
+   and create FIFOs. */
 bool set_fifonames( const std::string filenames[2] )
   {
   enum { num_codes = 36 };
@@ -152,10 +155,10 @@ bool set_data_feeder( const std::string & filename,
                       const std::string & fifoname, const int infd,
                       Children & children, int format_index )
   {
-  const uint8_t * magic_data = 0;
+  uint8_t magic_data[magic_buf_size];
   int magic_size = 0;
   if( format_index < 0 )
-    format_index = test_format( infd, &magic_data, &magic_size );
+    format_index = test_format( infd, magic_data, &magic_size );
   children.compressor_name = get_compressor_name( format_index );
 
   if( children.compressor_name )	// compressed
@@ -264,8 +267,8 @@ int main( const int argc, const char * const argv[] )
   enum { bz2_opt = 256, gz_opt, lz_opt, xz_opt };
   std::vector< const char * > diff_args;	// args to diff, maybe empty
   int format_types[2] = { -1, -1 };
-  invocation_name = argv[0];
   program_name = "zdiff";
+  invocation_name = ( argc > 0 ) ? argv[0] : program_name;
 
   const Arg_parser::Option options[] =
     {
@@ -290,6 +293,8 @@ int main( const int argc, const char * const argv[] )
     { 'U', "unified",                Arg_parser::yes },
     { 'V', "version",                Arg_parser::no  },
     { 'w', "ignore-all-space",       Arg_parser::no  },
+    { 'W', "width",                  Arg_parser::yes },
+    { 'y', "side-by-side",           Arg_parser::no  },
     { bz2_opt,    "bz2",             Arg_parser::yes },
     { gz_opt,     "gz",              Arg_parser::yes },
     { lz_opt,     "lz",              Arg_parser::yes },
@@ -333,6 +338,9 @@ int main( const int argc, const char * const argv[] )
                 diff_args.push_back( arg.c_str() ); break;
       case 'V': show_version(); return 0;
       case 'w': diff_args.push_back( "-w" ); break;
+      case 'W': diff_args.push_back( "-W" );
+                diff_args.push_back( arg.c_str() ); break;
+      case 'y': diff_args.push_back( "-y" ); break;
       case bz2_opt: parse_compressor( arg, fmt_bz2 ); break;
       case gz_opt: parse_compressor( arg, fmt_gz ); break;
       case lz_opt: parse_compressor( arg, fmt_lz ); break;
@@ -361,25 +369,30 @@ int main( const int argc, const char * const argv[] )
     STDIN_FILENO : open_instream( filenames[0] );
   if( infd[0] < 0 ) return 2;
 
-  if( ( files == 1 && filenames[0] == "-" ) ||
-      ( files == 2 && check_identical( filenames[0].c_str(),
-                                       filenames[1].c_str() ) ) )
-    return 0;
-
   if( files == 2 )
     {
+    if( check_identical( filenames[0].c_str(), filenames[1].c_str() ) )
+      return 0;
     infd[1] = ( filenames[1] == "-" ) ?
       STDIN_FILENO : open_instream( filenames[1] );
     if( infd[1] < 0 ) return 2;
     }
   else
     {
+    if( filenames[0] == "-" )
+      { show_error( "Missing operand after '-'.", 0, true ); return 2; }
     if( format_types[0] >= 0 || format_types[1] >= 0 )
       { show_error( "Two files must be given when format is specified.", 0, true );
         return 2; }
     filenames[1] = filenames[0];
     infd[1] = open_other_instream( filenames[1] );
-    if( infd[1] < 0 ) { infd[1] = STDIN_FILENO; filenames[1] = "-"; }
+    if( infd[1] < 0 )
+      {
+      if( verbosity >= 0 )
+        std::fprintf( stderr, "%s: Can't find file to compare with '%s'.\n",
+                      program_name, filenames[0].c_str() );
+      show_error( 0, 0, true ); return 2;
+      }
     }
 
   std::atexit( remove_fifos );
diff --git a/zgrep.cc b/zgrep.cc
index 1013b5e..01c6b07 100644
--- a/zgrep.cc
+++ b/zgrep.cc
@@ -1,18 +1,18 @@
-/*  Zgrep - search compressed files for a regular expression
-    Copyright (C) 2010-2019 Antonio Diaz Diaz.
+/* Zgrep - search compressed files for a regular expression
+   Copyright (C) 2010-2020 Antonio Diaz Diaz.
 
-    This program is free software: you can redistribute it and/or modify
-    it under the terms of the GNU General Public License as published by
-    the Free Software Foundation, either version 2 of the License, or
-    (at your option) any later version.
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 2 of the License, or
+   (at your option) any later version.
 
-    This program is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-    GNU General Public License for more details.
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
 
-    You should have received a copy of the GNU General Public License
-    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
 #define _FILE_OFFSET_BITS 64
@@ -47,21 +47,23 @@ namespace {
 
 void show_help()
   {
-  std::printf( "Zgrep is a front end to the grep program that allows transparent search\n"
-               "on any combination of compressed and uncompressed files. If any given\n"
-               "file is compressed, its decompressed content is used. If a given file\n"
+  std::printf( "zgrep is a front end to the program grep that allows transparent search\n"
+               "on any combination of compressed and uncompressed files. If any file\n"
+               "given is compressed, its decompressed content is used. If a file given\n"
                "does not exist, and its name does not end with one of the known\n"
                "extensions, zgrep tries the compressed file names corresponding to the\n"
-               "formats supported.\n"
+               "formats supported. If a file fails to decompress, zgrep continues\n"
+               "searching the rest of the files.\n"
                "\nIf a file is specified as '-', data are read from standard input,\n"
                "decompressed if needed, and fed to grep. Data read from standard input\n"
                "must be of the same type; all uncompressed or all in the same\n"
-               "compression format.\n"
+               "compressed format.\n"
                "\nIf no files are specified, recursive searches examine the current\n"
                "working directory, and nonrecursive searches read standard input.\n"
-               "\nThe formats supported are bzip2, gzip, lzip and xz.\n"
+               "\nThe formats supported are bzip2, gzip, lzip, and xz.\n"
                "\nUsage: zgrep [options] <pattern> [files]\n"
                "\nExit status is 0 if match, 1 if no match, 2 if trouble.\n"
+               "Some options only work if the grep program used supports them.\n"
                "\nOptions:\n"
                "      --help                   display this help and exit\n"
                "  -V, --version                output version information and exit\n"
@@ -87,7 +89,7 @@ void show_help()
                "  -n, --line-number            print the line number of each line\n"
                "  -N, --no-rcfile              don't read runtime configuration file\n"
                "  -o, --only-matching          show only the part of a line matching <pattern>\n"
-               "  -O, --force-format=<fmt>     force given format (bz2, gz, lz, xz)\n"
+               "  -O, --force-format=<fmt>     force the format given (bz2, gz, lz, xz)\n"
                "  -q, --quiet                  suppress all messages\n"
                "  -r, --recursive              operate recursively on directories\n"
                "  -R, --dereference-recursive  recursively follow symbolic links\n"
@@ -100,7 +102,7 @@ void show_help()
                "      --gz=<command>           set compressor and options for gzip format\n"
                "      --lz=<command>           set compressor and options for lzip format\n"
                "      --xz=<command>           set compressor and options for xz format\n"
-               "Numbers may be followed by a multiplier: k = kB = 10^3 = 1000,\n"
+               "\nNumbers may be followed by a multiplier: k = kB = 10^3 = 1000,\n"
                "Ki = KiB = 2^10 = 1024, M = 10^6, Mi = 2^20, G = 10^9, Gi = 2^30, etc...\n" );
   show_help_addr();
   }
@@ -217,15 +219,15 @@ int main( const int argc, const char * const argv[] )
   enum { help_opt = 256, verbose_opt, color_opt,
          bz2_opt, gz_opt, lz_opt, xz_opt };
   int format_index = -1;
-  int list_mode = 0;		// 1 = list matches, -1 = list non matches
+  int list_mode = 0;		// 1 = list matches, -1 = list non-matches
   int recursive = 0;		// 1 = '-r', 2 = '-R'
   int show_name = -1;		// tri-state bool
   bool no_messages = false;
   std::list< std::string > filenames;
   std::vector< const char * > grep_args;	// args to grep, maybe empty
   std::string color_option;		// needed because of optional arg
-  invocation_name = argv[0];
   program_name = "zgrep";
+  invocation_name = ( argc > 0 ) ? argv[0] : program_name;
 
   const Arg_parser::Option options[] =
     {
@@ -365,10 +367,10 @@ int main( const int argc, const char * const argv[] )
                         false, no_messages ) )
     {
     int infd;
-    if( input_filename.empty() )
+    if( input_filename == "." )
       {
       if( stdin_used ) continue; else stdin_used = true;
-      infd = STDIN_FILENO;
+      infd = STDIN_FILENO; input_filename = "-";
       }
     else
       {
@@ -383,7 +385,9 @@ int main( const int argc, const char * const argv[] )
                            list_mode, show_name );
     if( tmp == 0 || ( tmp == 2 && retval == 1 ) ) retval = tmp;
 
-    if( input_filename.size() ) close( infd );
+    if( close( infd ) != 0 )
+      { show_file_error( input_filename.c_str(), "Error closing input file",
+                         errno ); error = true; }
     if( retval == 0 && verbosity < 0 ) break;
     }
 
diff --git a/ztest.cc b/ztest.cc
index 5037fbf..a059a5b 100644
--- a/ztest.cc
+++ b/ztest.cc
@@ -1,18 +1,18 @@
-/*  Ztest - verify the integrity of compressed files
-    Copyright (C) 2010-2019 Antonio Diaz Diaz.
+/* Ztest - verify the integrity of compressed files
+   Copyright (C) 2010-2020 Antonio Diaz Diaz.
 
-    This program is free software: you can redistribute it and/or modify
-    it under the terms of the GNU General Public License as published by
-    the Free Software Foundation, either version 2 of the License, or
-    (at your option) any later version.
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 2 of the License, or
+   (at your option) any later version.
 
-    This program is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-    GNU General Public License for more details.
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
 
-    You should have received a copy of the GNU General Public License
-    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
 #define _FILE_OFFSET_BITS 64
@@ -50,13 +50,17 @@ namespace {
 
 void show_help()
   {
-  std::printf( "Ztest verifies the integrity of the specified compressed files.\n"
+  std::printf( "ztest verifies the integrity of the compressed files specified.\n"
                "Uncompressed files are ignored. If a file is specified as '-', the\n"
                "integrity of compressed data read from standard input is verified. Data\n"
-               "read from standard input must be all in the same compression format.\n"
+               "read from standard input must be all in the same compressed format. If\n"
+               "a file fails to decompress, does not exist, can't be opened, or is a\n"
+               "terminal, ztest continues verifying the rest of the files. A final\n"
+               "diagnostic is shown at verbosity level 1 or higher if any file fails the\n"
+               "test when testing multiple files.\n"
                "\nIf no files are specified, recursive searches examine the current\n"
                "working directory, and nonrecursive searches read standard input.\n"
-               "\nThe formats supported are bzip2, gzip, lzip and xz.\n"
+               "\nThe formats supported are bzip2, gzip, lzip, and xz.\n"
                "\nNote that error detection in the xz format is broken. First, some xz\n"
                "files lack integrity information. Second, not all xz decompressors can\n"
                "verify the integrity of all xz files. Third, section 2.1.1.2 'Stream\n"
@@ -72,7 +76,7 @@ void show_help()
                "  -V, --version                output version information and exit\n"
                "  -M, --format=<list>          process only the formats in <list>\n"
                "  -N, --no-rcfile              don't read runtime configuration file\n"
-               "  -O, --force-format=<fmt>     force given format (bz2, gz, lz, xz)\n"
+               "  -O, --force-format=<fmt>     force the format given (bz2, gz, lz, xz)\n"
                "  -q, --quiet                  suppress all messages\n"
                "  -r, --recursive              operate recursively on directories\n"
                "  -R, --dereference-recursive  recursively follow symbolic links\n"
@@ -97,10 +101,10 @@ int open_instream( const std::string & input_filename )
 int ztest_stdin( const int infd, int format_index,
                  const std::vector< const char * > & ztest_args )
   {
-  const uint8_t * magic_data = 0;
+  uint8_t magic_data[magic_buf_size];
   int magic_size = 0;
   if( format_index < 0 )
-    format_index = test_format( infd, &magic_data, &magic_size );
+    format_index = test_format( infd, magic_data, &magic_size );
   const char * const compressor_name = get_compressor_name( format_index );
   if( !compressor_name )
     { show_error( "Unknown data format read from stdin." ); return 2; }
@@ -161,10 +165,10 @@ int ztest_file( const int infd, int format_index,
                 const std::vector< const char * > & ztest_args )
   {
   static int disable_xz = -1;				// tri-state bool
-  const uint8_t * magic_data = 0;
+  uint8_t magic_data[magic_buf_size];
   int magic_size = 0;
   if( format_index < 0 )
-    format_index = test_format( infd, &magic_data, &magic_size );
+    format_index = test_format( infd, magic_data, &magic_size );
   const char * const compressor_name = get_compressor_name( format_index );
   if( !compressor_name )
     return 0;				// ignore this file
@@ -217,8 +221,8 @@ int main( const int argc, const char * const argv[] )
   int recursive = 0;				// 1 = '-r', 2 = '-R'
   std::list< std::string > filenames;
   std::vector< const char * > ztest_args;	// args to ztest, maybe empty
-  invocation_name = argv[0];
   program_name = "ztest";
+  invocation_name = ( argc > 0 ) ? argv[0] : program_name;
 
   const Arg_parser::Option options[] =
     {
@@ -280,16 +284,17 @@ int main( const int argc, const char * const argv[] )
   if( filenames.empty() ) filenames.push_back( recursive ? "." : "-" );
 
   std::string input_filename;
+  int files_tested = 0, failed_tests = 0;
   int retval = 0;
   bool error = false;
   bool stdin_used = false;
   while( next_filename( filenames, input_filename, error, recursive ) )
     {
     int infd;
-    if( input_filename.empty() )
+    if( input_filename == "." )
       {
       if( stdin_used ) continue; else stdin_used = true;
-      infd = STDIN_FILENO;
+      infd = STDIN_FILENO; input_filename = "-";
       }
     else
       {
@@ -297,13 +302,23 @@ int main( const int argc, const char * const argv[] )
       if( infd < 0 ) { error = true; continue; }
       }
 
+    if( isatty( infd ) )			// for example /dev/tty
+      {
+      show_file_error( input_filename == "-" ? "(stdin)" : input_filename.c_str(),
+                       "I won't read compressed data from a terminal." );
+      close( infd ); error = true; continue;
+      }
+
     int tmp;
     if( infd == STDIN_FILENO )
       tmp = ztest_stdin( infd, format_index, ztest_args );
     else tmp = ztest_file( infd, format_index, input_filename, ztest_args );
     if( tmp > retval ) retval = tmp;
+    ++files_tested; if( tmp ) ++failed_tests;
 
-    if( input_filename.size() ) close( infd );
+    if( close( infd ) != 0 )
+      { show_file_error( input_filename.c_str(), "Error closing input file",
+                         errno ); error = true; }
     }
 
   if( std::fclose( stdout ) != 0 )	// in case decompressor writes to stdout
@@ -312,5 +327,9 @@ int main( const int argc, const char * const argv[] )
     error = true;
     }
   if( error && retval == 0 ) retval = 1;
+  if( failed_tests > 0 && verbosity >= 1 && files_tested > 1 )
+    std::fprintf( stderr, "%s: warning: %d %s failed the test.\n",
+                  program_name, failed_tests,
+                  ( failed_tests == 1 ) ? "file" : "files" );
   return retval;
   }
diff --git a/zupdate.cc b/zupdate.cc
index dec65f4..cc0ffde 100644
--- a/zupdate.cc
+++ b/zupdate.cc
@@ -1,18 +1,18 @@
-/*  Zupdate - recompress bzip2, gzip, xz files to lzip format
-    Copyright (C) 2013-2019 Antonio Diaz Diaz.
+/* Zupdate - recompress bzip2, gzip, xz files to lzip format
+   Copyright (C) 2013-2020 Antonio Diaz Diaz.
 
-    This program is free software: you can redistribute it and/or modify
-    it under the terms of the GNU General Public License as published by
-    the Free Software Foundation, either version 2 of the License, or
-    (at your option) any later version.
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 2 of the License, or
+   (at your option) any later version.
 
-    This program is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-    GNU General Public License for more details.
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
 
-    You should have received a copy of the GNU General Public License
-    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
 #define _FILE_OFFSET_BITS 64
@@ -51,7 +51,7 @@ namespace {
 
 void show_help()
   {
-  std::printf( "Zupdate recompresses files from bzip2, gzip, and xz formats to lzip\n"
+  std::printf( "zupdate recompresses files from bzip2, gzip, and xz formats to lzip\n"
                "format. Each original is compared with the new file and then deleted.\n"
                "Only regular files with standard file name extensions are recompressed,\n"
                "other files are ignored. Compressed files are decompressed and then\n"
@@ -61,21 +61,23 @@ void show_help()
                "\nIf no files are specified, recursive searches examine the current\n"
                "working directory, and nonrecursive searches do nothing.\n"
                "\nIf the lzip compressed version of a file already exists, the file is\n"
-               "skipped unless the '--force' option is given. In this case, if the\n"
+               "skipped unless the option '--force' is given. In this case, if the\n"
                "comparison with the existing lzip version fails, an error is returned\n"
                "and the original file is not deleted. The operation of zupdate is meant\n"
-               "to be safe and not produce any data loss. Therefore, existing lzip\n"
+               "to be safe and not cause any data loss. Therefore, existing lzip\n"
                "compressed files are never overwritten nor deleted.\n"
+               "\nThe names of the original files must have one of the following extensions:\n"
+               "'.bz2', '.gz', and '.xz' are recompressed to '.lz'.\n"
+               "'.tbz', '.tbz2', '.tgz', and '.txz' are recompressed to '.tlz'.\n"
                "\nUsage: zupdate [options] [files]\n"
-               "\nExit status is 0 if all the compressed files were successfully\n"
-               "recompressed (if needed), compared and deleted (if requested). Non-zero\n"
-               "otherwise.\n"
+               "\nExit status is 0 if all the compressed files were successfully recompressed\n"
+               "(if needed), compared, and deleted (if requested). Non-zero otherwise.\n"
                "\nOptions:\n"
                "  -h, --help                   display this help and exit\n"
                "  -V, --version                output version information and exit\n"
                "  -f, --force                  don't skip a file even if the .lz exists\n"
                "  -k, --keep                   keep (don't delete) input files\n"
-               "  -l, --lzip-verbose           pass a -v option to the lzip compressor\n"
+               "  -l, --lzip-verbose           pass one option -v to the lzip compressor\n"
                "  -M, --format=<list>          process only the formats in <list>\n"
                "  -N, --no-rcfile              don't read runtime configuration file\n"
                "  -q, --quiet                  suppress all messages\n"
@@ -106,7 +108,7 @@ int cant_execute( const std::string & command, const int status )
   }
 
 
-     // Set permissions, owner and times.
+// Set permissions, owner, and times.
 void set_permissions( const char * const rname, const struct stat & in_stats )
   {
   bool warning = false;
@@ -135,7 +137,7 @@ int zupdate_file( const std::string & name, const char * const lzip_name,
   {
   static int disable_xz = -1;				// tri-state bool
   int format_index = -1;
-  std::string dname;					// decompressed_name
+  std::string rname;					// recompressed name
 
   const int eindex = extension_index( name );		// search extension
   if( eindex >= 0 )
@@ -148,8 +150,9 @@ int zupdate_file( const std::string & name, const char * const lzip_name,
                       program_name, name.c_str(), extension_from( eindex ) );
       return 0;					// ignore this file
       }
-    dname.assign( name, 0, name.size() - std::strlen( extension_from( eindex ) ) );
-    dname += extension_to( eindex );
+    rname.assign( name, 0, name.size() - std::strlen( extension_from( eindex ) ) );
+    rname += ( std::strcmp( extension_to( eindex ), ".tar" ) == 0 ) ?
+             ".tlz" : ".lz";			// keep combined extension
     }
   const char * const compressor_name = get_compressor_name( format_index );
   if( !compressor_name )
@@ -176,9 +179,11 @@ int zupdate_file( const std::string & name, const char * const lzip_name,
     return 1;
     }
 
-  struct stat st;
-  std::string rname( dname ); rname += ".lz";		// recompressed_name
+  struct stat st;				// not used
+  const std::string rname2( rname + ".lz" );	// produced by lzip < 1.20
   const bool lz_exists = ( stat( rname.c_str(), &st ) == 0 );
+  // don't modify an existing 'rname.lz'
+  const bool lz_lz_exists = ( stat( rname2.c_str(), &st ) == 0 );
   if( lz_exists && !force )
     {
     if( verbosity >= 0 )
@@ -245,7 +250,7 @@ int zupdate_file( const std::string & name, const char * const lzip_name,
         for( int i = 0; i < size; ++i ) argv[i+2] = lzip_args[i].c_str();
         for( int i = 0; i < size2; ++i ) argv[i+size+2] = lzip_args2[i].c_str();
         argv[size+size2+2] = "-o";
-        argv[size+size2+3] = dname.c_str();
+        argv[size+size2+3] = rname.c_str();
         argv[size+size2+4] = 0;
         execvp( argv[0], (char **)argv );
         }
@@ -258,7 +263,14 @@ int zupdate_file( const std::string & name, const char * const lzip_name,
     close( fda[0] ); close( fda[1] );
     int retval = wait_for_child( pid, compressor_name );
     int retval2 = wait_for_child( pid2, lzip_name );
-    if( retval || retval2 ) { std::remove( rname.c_str() ); return 1; }
+    if( retval || retval2 )
+      { if( !lz_lz_exists ) std::remove( rname2.c_str() );	// lzip < 1.20
+        std::remove( rname.c_str() ); return 1; }
+    if( stat( rname.c_str(), &st ) != 0 &&
+        ( lz_lz_exists || stat( rname2.c_str(), &st ) != 0 ||
+          std::rename( rname2.c_str(), rname.c_str() ) != 0 ) )
+      { show_file_error( rname.c_str(), "Error renaming output file", errno );
+        return 1; }						// lzip < 1.11
     set_permissions( rname.c_str(), in_stats );
     }
 
@@ -268,11 +280,12 @@ int zupdate_file( const std::string & name, const char * const lzip_name,
   std::string zcmp_command( invocation_name );
   unsigned i =  zcmp_command.size();
   while( i > 0 && zcmp_command[i-1] != '/' ) --i;
-  zcmp_command.resize( i );
-  zcmp_command += "zcmp ";				// ${bindir}zcmp
+  zcmp_command.resize( i ); zcmp_command.insert( 0U, 1, '\'' );
+  zcmp_command += "zcmp' ";				// '[dir/]zcmp'
   if( no_rcfile ) zcmp_command += "-N ";
   if( verbosity < 0 ) zcmp_command += "-q ";
-  zcmp_command += name; zcmp_command += ' '; zcmp_command += rname;
+  zcmp_command += '\''; zcmp_command += name;
+  zcmp_command += "' '"; zcmp_command += rname; zcmp_command += '\'';
   int status = std::system( zcmp_command.c_str() );
   if( status != 0 )
     { if( !lz_exists ) std::remove( rname.c_str() );
@@ -301,8 +314,8 @@ int main( const int argc, const char * const argv[] )
   bool force = false;
   bool keep_input_files = false;
   bool no_rcfile = false;
-  invocation_name = argv[0];
   program_name = "zupdate";
+  invocation_name = ( argc > 0 ) ? argv[0] : program_name;
 
   const Arg_parser::Option options[] =
     {
diff --git a/zutils.cc b/zutils.cc
index 74b7351..6090c0a 100644
--- a/zutils.cc
+++ b/zutils.cc
@@ -1,18 +1,18 @@
-/*  Zutils - Utilities dealing with compressed files
-    Copyright (C) 2009-2019 Antonio Diaz Diaz.
+/* Zutils - Utilities dealing with compressed files
+   Copyright (C) 2009-2020 Antonio Diaz Diaz.
 
-    This program is free software: you can redistribute it and/or modify
-    it under the terms of the GNU General Public License as published by
-    the Free Software Foundation, either version 2 of the License, or
-    (at your option) any later version.
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 2 of the License, or
+   (at your option) any later version.
 
-    This program is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-    GNU General Public License for more details.
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
 
-    You should have received a copy of the GNU General Public License
-    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
 #define _FILE_OFFSET_BITS 64
@@ -34,24 +34,21 @@
 
 namespace {
 
-// first magic byte must be different among formats
-enum { bzip2_magic_size = 3,
-        gzip_magic_size = 2,
-        lzip_magic_size = 4,
-          xz_magic_size = 5 };
-const uint8_t bzip2_magic[bzip2_magic_size] =
-  { 0x42, 0x5A, 0x68 };				// "BZh"
-const uint8_t gzip_magic[gzip_magic_size] =
-  { 0x1F, 0x8B };
-const uint8_t lzip_magic[lzip_magic_size] =
-  { 0x4C, 0x5A, 0x49, 0x50 };			// "LZIP"
-const uint8_t xz_magic[xz_magic_size] =
-  { 0xFD, 0x37, 0x7A, 0x58, 0x5A };		// 0xFD, "7zXZ"
+inline bool isvalid_ds( const uint8_t ds )	// lzip valid dictionary_size
+  {
+  enum { min_dictionary_size = 1 << 12,
+         max_dictionary_size = 1 << 29 };
+  unsigned dictionary_size = ( 1 << ( ds & 0x1F ) );
+  if( dictionary_size > min_dictionary_size )
+    dictionary_size -= ( dictionary_size / 16 ) * ( ( ds >> 5 ) & 7 );
+  return ( dictionary_size >= min_dictionary_size &&
+           dictionary_size <= max_dictionary_size );
+  }
 
 
-// Returns -1 if child not terminated, 2 in case of error, or
-// exit status of child process 'pid'.
-//
+/* Returns -1 if child not terminated, 2 in case of error, or exit status of
+   child process 'pid'.
+*/
 int child_status( const pid_t pid, const char * const name )
   {
   int status;
@@ -69,15 +66,16 @@ int child_status( const pid_t pid, const char * const name )
     if( tmp == pid ) break;			// child terminated
     }
   if( WIFEXITED( status ) ) return WEXITSTATUS( status );
+  if( WIFSIGNALED( status ) && WTERMSIG( status ) == SIGPIPE ) return 0;
   return 2;
   }
 
 } // end namespace
 
 
-// Returns the number of bytes really read.
-// If (returned value < size) and (errno == 0), means EOF was reached.
-//
+/* Returns the number of bytes really read.
+   If (returned value < size) and (errno == 0), means EOF was reached.
+*/
 int readblock( const int fd, uint8_t * const buf, const int size )
   {
   int sz = 0;
@@ -94,9 +92,9 @@ int readblock( const int fd, uint8_t * const buf, const int size )
   }
 
 
-// Returns the number of bytes really written.
-// If (returned value < size), it is always an error.
-//
+/* Returns the number of bytes really written.
+   If (returned value < size), it is always an error.
+*/
 int writeblock( const int fd, const uint8_t * const buf, const int size )
   {
   int sz = 0;
@@ -144,8 +142,9 @@ bool good_status( const Children & children, const bool finished )
     if( pid )
       {
       const char * const name =
-        ( i & 1 ) ? children.compressor_name : "data feeder";
-      if( !finished )
+        ( i == 0 ) ? "data feeder" : children.compressor_name;
+      // even if compressor finished, trailing data may remain in data feeder
+      if( i == 0 || !finished )
         {
         const int tmp = child_status( pid, name );
         if( tmp < 0 )				// child not terminated
@@ -163,10 +162,10 @@ bool good_status( const Children & children, const bool finished )
 bool set_data_feeder( const std::string & filename, int * const infdp,
                       Children & children, int format_index )
   {
-  const uint8_t * magic_data = 0;
+  uint8_t magic_data[magic_buf_size];
   int magic_size = 0;
   if( format_index < 0 )
-    format_index = test_format( *infdp, &magic_data, &magic_size );
+    format_index = test_format( *infdp, magic_data, &magic_size );
   children.compressor_name = get_compressor_name( format_index );
 
   if( children.compressor_name )	// compressed
@@ -247,46 +246,38 @@ bool set_data_feeder( const std::string & filename, int * const infdp,
   }
 
 
-int test_format( const int infd, const uint8_t ** const magic_datap,
+// Returns format index or -1 if uncompressed
+//
+int test_format( const int infd, uint8_t magic_data[],
                  int * const magic_sizep )
   {
-  enum { buf_size = 5 };
-  static uint8_t buf[buf_size];
-  int i = 0;
-  if( readblock( infd, buf, 1 ) == 1 )
+  enum { bzip2_magic_size = 3,
+          gzip_magic_size = 2,
+          lzip_magic_size = 5,
+            xz_magic_size = 5 };
+  const uint8_t bzip2_magic[bzip2_magic_size] =
+    { 0x42, 0x5A, 0x68 };				// "BZh"
+  const uint8_t gzip_magic[gzip_magic_size] =
+    { 0x1F, 0x8B };
+  const uint8_t lzip_magic[lzip_magic_size] =
+    { 0x4C, 0x5A, 0x49, 0x50, 0x01 };			// "LZIP\001"
+  const uint8_t xz_magic[xz_magic_size] =
+    { 0xFD, 0x37, 0x7A, 0x58, 0x5A };			// 0xFD, "7zXZ"
+
+  *magic_sizep = readblock( infd, magic_data, magic_buf_size );
+  if( *magic_sizep == magic_buf_size )
     {
-    ++i;
-    if( buf[0] == bzip2_magic[0] )
-      {
-      if( readblock( infd, &buf[i], 1 ) == 1 && buf[i++] == bzip2_magic[1] &&
-          readblock( infd, &buf[i], 1 ) == 1 && buf[i++] == bzip2_magic[2] )
-        { *magic_datap = bzip2_magic; *magic_sizep = bzip2_magic_size;
-          return fmt_bz2; }
-      }
-    else if( buf[0] == gzip_magic[0] )
-      {
-      if( readblock( infd, &buf[i], 1 ) == 1 && buf[i++] == gzip_magic[1] )
-        { *magic_datap = gzip_magic; *magic_sizep = gzip_magic_size;
-          return fmt_gz; }
-      }
-    else if( buf[0] == lzip_magic[0] )
-      {
-      if( readblock( infd, &buf[i], 1 ) == 1 && buf[i++] == lzip_magic[1] &&
-          readblock( infd, &buf[i], 1 ) == 1 && buf[i++] == lzip_magic[2] &&
-          readblock( infd, &buf[i], 1 ) == 1 && buf[i++] == lzip_magic[3] )
-        { *magic_datap = lzip_magic; *magic_sizep = lzip_magic_size;
-          return fmt_lz; }
-      }
-    else if( buf[0] == xz_magic[0] )
-      {
-      if( readblock( infd, &buf[i], 1 ) == 1 && buf[i++] == xz_magic[1] &&
-          readblock( infd, &buf[i], 1 ) == 1 && buf[i++] == xz_magic[2] &&
-          readblock( infd, &buf[i], 1 ) == 1 && buf[i++] == xz_magic[3] &&
-          readblock( infd, &buf[i], 1 ) == 1 && buf[i++] == xz_magic[4] )
-        { *magic_datap = xz_magic; *magic_sizep = xz_magic_size;
-          return fmt_xz; }
-      }
+    if( std::memcmp( magic_data, bzip2_magic, bzip2_magic_size ) == 0 &&
+        magic_data[3] >= '1' && magic_data[3] <= '9' &&
+        std::memcmp( magic_data + 4, "1AY&SY", 6 ) == 0 )
+      return fmt_bz2;
+    if( std::memcmp( magic_data, gzip_magic, gzip_magic_size ) == 0 )
+      return fmt_gz;
+    if( std::memcmp( magic_data, lzip_magic, lzip_magic_size ) == 0 &&
+        isvalid_ds( magic_data[lzip_magic_size] ) )
+      return fmt_lz;
+    if( std::memcmp( magic_data, xz_magic, xz_magic_size ) == 0 )
+      return fmt_xz;
     }
-  *magic_datap = buf; *magic_sizep = i;
   return -1;
   }
diff --git a/zutils.h b/zutils.h
index f05be62..ef7248a 100644
--- a/zutils.h
+++ b/zutils.h
@@ -1,18 +1,18 @@
-/*  Zutils - Utilities dealing with compressed files
-    Copyright (C) 2009-2019 Antonio Diaz Diaz.
+/* Zutils - Utilities dealing with compressed files
+   Copyright (C) 2009-2020 Antonio Diaz Diaz.
 
-    This program is free software: you can redistribute it and/or modify
-    it under the terms of the GNU General Public License as published by
-    the Free Software Foundation, either version 2 of the License, or
-    (at your option) any later version.
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 2 of the License, or
+   (at your option) any later version.
 
-    This program is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-    GNU General Public License for more details.
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
 
-    You should have received a copy of the GNU General Public License
-    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
 int readblock( const int fd, uint8_t * const buf, const int size );
@@ -29,7 +29,9 @@ bool good_status( const Children & children, const bool finished );
 bool set_data_feeder( const std::string & filename, int * const infdp,
                       Children & children, int format_index );
 
+enum { magic_buf_size = 10 };		// >= longest extended magic (bzip2)
+
 // Returns format index or -1 if uncompressed
 //
-int test_format( const int infd, const uint8_t ** const magic_datap,
+int test_format( const int infd, uint8_t magic_data[],
                  int * const magic_sizep );