Merging upstream version 1.11.

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

8 files changed, 311 insertions, 157 deletions

diff --git a/doc/zcat.1 b/doc/zcat.1
index fbaf821..67b580c 100644
--- a/doc/zcat.1
+++ b/doc/zcat.1
@@ -1,5 +1,5 @@
 .\" DO NOT MODIFY THIS FILE!  It was generated by help2man 1.47.16.
-.TH ZCAT "1" "January 2021" "zutils 1.10" "User Commands"
+.TH ZCAT "1" "January 2022" "zutils 1.11" "User Commands"
 .SH NAME
 zcat \- decompress and concatenate files to standard output
 .SH SYNOPSIS
@@ -21,7 +21,7 @@ same compressed format.
 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, xz, and zstd.
 .PP
 Exit status is 0 if no errors occurred, 1 otherwise.
 .SH OPTIONS
@@ -54,7 +54,7 @@ number all output lines
 don't read runtime configuration file
 .TP
 \fB\-O\fR, \fB\-\-force\-format=\fR<fmt>
-force the format given (bz2, gz, lz, xz)
+force the format given (bz2, gz, lz, xz, zst)
 .TP
 \fB\-q\fR, \fB\-\-quiet\fR
 suppress all messages
@@ -91,13 +91,28 @@ set compressor and options for lzip format
 .TP
 \fB\-\-xz=\fR<command>
 set compressor and options for xz format
+.TP
+\fB\-\-zst=\fR<command>
+set compressor and options for zstd format
 .SH "REPORTING BUGS"
 Report bugs to zutils\-bug@nongnu.org
 .br
 Zutils home page: http://www.nongnu.org/zutils/zutils.html
 .SH COPYRIGHT
-Copyright \(co 2021 Antonio Diaz Diaz.
+Copyright \(co 2022 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.
 There is NO WARRANTY, to the extent permitted by law.
+.SH "SEE ALSO"
+The full documentation for
+.B zcat
+is maintained as a Texinfo manual.  If the
+.B info
+and
+.B zcat
+programs are properly installed at your site, the command
+.IP
+.B info zutils
+.PP
+should give you access to the complete manual.
diff --git a/doc/zcmp.1 b/doc/zcmp.1
index 5ae5231..3f23287 100644
--- a/doc/zcmp.1
+++ b/doc/zcmp.1
@@ -1,5 +1,5 @@
 .\" DO NOT MODIFY THIS FILE!  It was generated by help2man 1.47.16.
-.TH ZCMP "1" "January 2021" "zutils 1.10" "User Commands"
+.TH ZCMP "1" "January 2022" "zutils 1.11" "User Commands"
 .SH NAME
 zcmp \- decompress and compare two files byte by byte
 .SH SYNOPSIS
@@ -12,7 +12,7 @@ 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, xz, and zstd.
 .PP
 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
@@ -23,7 +23,7 @@ the corresponding uncompressed file (the name of file1 with the
 extension removed).
 .IP
 \- If file1 is uncompressed, compares it with the decompressed
-contents of file1.[lz|bz2|gz|xz] (the first one that is found).
+contents of file1.[lz|bz2|gz|zst|xz] (the first one that is found).
 .PP
 Exit status is 0 if inputs are identical, 1 if different, 2 if trouble.
 .SH OPTIONS
@@ -53,7 +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 the formats given (bz2, gz, lz, xz)
+force the formats given (bz2,gz,lz,xz,zst)
 .TP
 \fB\-q\fR, \fB\-\-quiet\fR
 suppress all messages
@@ -75,6 +75,9 @@ set compressor and options for lzip format
 .TP
 \fB\-\-xz=\fR<command>
 set compressor and options for xz format
+.TP
+\fB\-\-zst=\fR<command>
+set compressor and options for zstd format
 .PP
 Numbers may be followed by a multiplier: k = kB = 10^3 = 1000,
 Ki = KiB = 2^10 = 1024, M = 10^6, Mi = 2^20, G = 10^9, Gi = 2^30, etc...
@@ -83,8 +86,20 @@ Report bugs to zutils\-bug@nongnu.org
 .br
 Zutils home page: http://www.nongnu.org/zutils/zutils.html
 .SH COPYRIGHT
-Copyright \(co 2021 Antonio Diaz Diaz.
+Copyright \(co 2022 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.
 There is NO WARRANTY, to the extent permitted by law.
+.SH "SEE ALSO"
+The full documentation for
+.B zcmp
+is maintained as a Texinfo manual.  If the
+.B info
+and
+.B zcmp
+programs are properly installed at your site, the command
+.IP
+.B info zutils
+.PP
+should give you access to the complete manual.
diff --git a/doc/zdiff.1 b/doc/zdiff.1
index 65a34b7..784ef7b 100644
--- a/doc/zdiff.1
+++ b/doc/zdiff.1
@@ -1,5 +1,5 @@
 .\" DO NOT MODIFY THIS FILE!  It was generated by help2man 1.47.16.
-.TH ZDIFF "1" "January 2021" "zutils 1.10" "User Commands"
+.TH ZDIFF "1" "January 2022" "zutils 1.11" "User Commands"
 .SH NAME
 zdiff \- decompress and compare two files line by line
 .SH SYNOPSIS
@@ -12,7 +12,9 @@ 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.
+\&'zdiff \fB\-v\fR \fB\-V\fR' prints the version of the diff program used.
+.PP
+The formats supported are bzip2, gzip, lzip, xz, and zstd.
 .PP
 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
@@ -23,7 +25,7 @@ the corresponding uncompressed file (the name of file1 with the
 extension removed).
 .IP
 \- If file1 is uncompressed, compares it with the decompressed
-contents of file1.[lz|bz2|gz|xz] (the first one that is found).
+contents of file1.[lz|bz2|gz|zst|xz] (the first one that is found).
 .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.
@@ -66,7 +68,7 @@ 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 the formats given (bz2, gz, lz, xz)
+force the formats given (bz2,gz,lz,xz,zst)
 .TP
 \fB\-p\fR, \fB\-\-show\-c\-function\fR
 show which C function each change is in
@@ -89,6 +91,9 @@ use the unified output format
 \fB\-U\fR, \fB\-\-unified=\fR<n>
 same as \fB\-u\fR but use <n> lines of context
 .TP
+\fB\-v\fR, \fB\-\-verbose\fR
+verbose mode (for \fB\-\-version\fR)
+.TP
 \fB\-w\fR, \fB\-\-ignore\-all\-space\fR
 ignore all white space
 .TP
@@ -109,13 +114,28 @@ set compressor and options for lzip format
 .TP
 \fB\-\-xz=\fR<command>
 set compressor and options for xz format
+.TP
+\fB\-\-zst=\fR<command>
+set compressor and options for zstd format
 .SH "REPORTING BUGS"
 Report bugs to zutils\-bug@nongnu.org
 .br
 Zutils home page: http://www.nongnu.org/zutils/zutils.html
 .SH COPYRIGHT
-Copyright \(co 2021 Antonio Diaz Diaz.
+Copyright \(co 2022 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.
 There is NO WARRANTY, to the extent permitted by law.
+.SH "SEE ALSO"
+The full documentation for
+.B zdiff
+is maintained as a Texinfo manual.  If the
+.B info
+and
+.B zdiff
+programs are properly installed at your site, the command
+.IP
+.B info zutils
+.PP
+should give you access to the complete manual.
diff --git a/doc/zgrep.1 b/doc/zgrep.1
index 69ed0cd..f3177bb 100644
--- a/doc/zgrep.1
+++ b/doc/zgrep.1
@@ -1,5 +1,5 @@
 .\" DO NOT MODIFY THIS FILE!  It was generated by help2man 1.47.16.
-.TH ZGREP "1" "January 2021" "zutils 1.10" "User Commands"
+.TH ZGREP "1" "January 2022" "zutils 1.11" "User Commands"
 .SH NAME
 zgrep \- search compressed files for a regular expression
 .SH SYNOPSIS
@@ -22,7 +22,9 @@ compressed format.
 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.
+\&'zgrep \fB\-\-verbose\fR \fB\-V\fR' prints the version of the grep program used.
+.PP
+The formats supported are bzip2, gzip, lzip, xz, and zstd.
 .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.
@@ -68,10 +70,10 @@ obtain patterns from <file>
 <pattern> is a set of newline\-separated strings
 .TP
 \fB\-h\fR, \fB\-\-no\-filename\fR
-suppress the prefixing filename on output
+suppress the prefixing file name on output
 .TP
 \fB\-H\fR, \fB\-\-with\-filename\fR
-print the filename for each match
+print the file name for each match
 .TP
 \fB\-i\fR, \fB\-\-ignore\-case\fR
 ignore case distinctions
@@ -101,7 +103,7 @@ 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 the format given (bz2, gz, lz, xz)
+force the format given (bz2, gz, lz, xz, zst)
 .TP
 \fB\-q\fR, \fB\-\-quiet\fR
 suppress all messages
@@ -138,6 +140,9 @@ set compressor and options for lzip format
 .TP
 \fB\-\-xz=\fR<command>
 set compressor and options for xz format
+.TP
+\fB\-\-zst=\fR<command>
+set compressor and options for zstd format
 .PP
 Numbers may be followed by a multiplier: k = kB = 10^3 = 1000,
 Ki = KiB = 2^10 = 1024, M = 10^6, Mi = 2^20, G = 10^9, Gi = 2^30, etc...
@@ -146,8 +151,20 @@ Report bugs to zutils\-bug@nongnu.org
 .br
 Zutils home page: http://www.nongnu.org/zutils/zutils.html
 .SH COPYRIGHT
-Copyright \(co 2021 Antonio Diaz Diaz.
+Copyright \(co 2022 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.
 There is NO WARRANTY, to the extent permitted by law.
+.SH "SEE ALSO"
+The full documentation for
+.B zgrep
+is maintained as a Texinfo manual.  If the
+.B info
+and
+.B zgrep
+programs are properly installed at your site, the command
+.IP
+.B info zutils
+.PP
+should give you access to the complete manual.
diff --git a/doc/ztest.1 b/doc/ztest.1
index 45cda27..210948e 100644
--- a/doc/ztest.1
+++ b/doc/ztest.1
@@ -1,5 +1,5 @@
 .\" DO NOT MODIFY THIS FILE!  It was generated by help2man 1.47.16.
-.TH ZTEST "1" "January 2021" "zutils 1.10" "User Commands"
+.TH ZTEST "1" "January 2022" "zutils 1.11" "User Commands"
 .SH NAME
 ztest \- verify the integrity of compressed files
 .SH SYNOPSIS
@@ -18,7 +18,7 @@ test when testing multiple files.
 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, xz, and zstd.
 .PP
 Note that error detection in the xz format is broken. First, some xz
 files lack integrity information. Second, not all xz decompressors can
@@ -45,7 +45,7 @@ process only the formats in <list>
 don't read runtime configuration file
 .TP
 \fB\-O\fR, \fB\-\-force\-format=\fR<fmt>
-force the format given (bz2, gz, lz, xz)
+force the format given (bz2, gz, lz, xz, zst)
 .TP
 \fB\-q\fR, \fB\-\-quiet\fR
 suppress all messages
@@ -70,13 +70,28 @@ set compressor and options for lzip format
 .TP
 \fB\-\-xz=\fR<command>
 set compressor and options for xz format
+.TP
+\fB\-\-zst=\fR<command>
+set compressor and options for zstd format
 .SH "REPORTING BUGS"
 Report bugs to zutils\-bug@nongnu.org
 .br
 Zutils home page: http://www.nongnu.org/zutils/zutils.html
 .SH COPYRIGHT
-Copyright \(co 2021 Antonio Diaz Diaz.
+Copyright \(co 2022 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.
 There is NO WARRANTY, to the extent permitted by law.
+.SH "SEE ALSO"
+The full documentation for
+.B ztest
+is maintained as a Texinfo manual.  If the
+.B info
+and
+.B ztest
+programs are properly installed at your site, the command
+.IP
+.B info zutils
+.PP
+should give you access to the complete manual.
diff --git a/doc/zupdate.1 b/doc/zupdate.1
index dcd3d24..b1e6472 100644
--- a/doc/zupdate.1
+++ b/doc/zupdate.1
@@ -1,12 +1,12 @@
 .\" DO NOT MODIFY THIS FILE!  It was generated by help2man 1.47.16.
-.TH ZUPDATE "1" "January 2021" "zutils 1.10" "User Commands"
+.TH ZUPDATE "1" "January 2022" "zutils 1.11" "User Commands"
 .SH NAME
-zupdate \- recompress bzip2, gzip, xz files to lzip format
+zupdate \- recompress bzip2, gzip, xz, zstd 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, xz, and zstd 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
@@ -25,8 +25,10 @@ to be safe and not cause any data loss. Therefore, existing lzip
 compressed files are never overwritten nor deleted.
 .PP
 The names of the original files must have one of the following extensions:
-\&'.bz2', '.gz', or '.xz', which are recompressed to '.lz';
-\&'.tbz', '.tbz2', '.tgz', or '.txz', which are recompressed to '.tlz'.
+.PP
+\&'.bz2', '.gz', '.xz', or '.zst', which are recompressed to '.lz'.
+.PP
+\&'.tbz', '.tbz2', '.tgz', '.txz', or '.tzst', which 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.
@@ -79,13 +81,28 @@ set compressor and options for lzip format
 .TP
 \fB\-\-xz=\fR<command>
 set compressor and options for xz format
+.TP
+\fB\-\-zst=\fR<command>
+set compressor and options for zstd format
 .SH "REPORTING BUGS"
 Report bugs to zutils\-bug@nongnu.org
 .br
 Zutils home page: http://www.nongnu.org/zutils/zutils.html
 .SH COPYRIGHT
-Copyright \(co 2021 Antonio Diaz Diaz.
+Copyright \(co 2022 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.
 There is NO WARRANTY, to the extent permitted by law.
+.SH "SEE ALSO"
+The full documentation for
+.B zupdate
+is maintained as a Texinfo manual.  If the
+.B info
+and
+.B zupdate
+programs are properly installed at your site, the command
+.IP
+.B info zutils
+.PP
+should give you access to the complete manual.
diff --git a/doc/zutils.info b/doc/zutils.info
index 854100f..a75b183 100644
--- a/doc/zutils.info
+++ b/doc/zutils.info
@@ -1,6 +1,6 @@
 This is zutils.info, produced by makeinfo version 4.13+ from zutils.texi.
 
-INFO-DIR-SECTION Data Compression
+INFO-DIR-SECTION Compression
 START-INFO-DIR-ENTRY
 * Zutils: (zutils).             Utilities dealing with compressed files
 END-INFO-DIR-ENTRY
@@ -11,7 +11,7 @@ File: zutils.info,  Node: Top,  Next: Introduction,  Up: (dir)
 Zutils Manual
 *************
 
-This manual is for Zutils (version 1.10, 5 January 2021).
+This manual is for Zutils (version 1.11, 25 January 2022).
 
 * Menu:
 
@@ -28,7 +28,7 @@ This manual is for Zutils (version 1.10, 5 January 2021).
 * Concept index::       Index of concepts
 
 
-   Copyright (C) 2009-2021 Antonio Diaz Diaz.
+   Copyright (C) 2009-2022 Antonio Diaz Diaz.
 
    This manual is free documentation: you have unlimited permission to copy,
 distribute, and modify it.
@@ -50,7 +50,7 @@ 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.
+The formats supported are bzip2, gzip, lzip, xz, and zstd.
 Zutils uses external compressors. The compressor to be used for each format
 is configurable at runtime.
 
@@ -60,12 +60,14 @@ 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
+values, making them less reliable back ends for zutils. Zstd currently does
+not even document its exit status in its man page. *Note
 compressor-requirements::.
 
    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'.
+of formats in recursive mode and when trying compressed file names. For
+example, use the following command to search for the string 'foo' in gzip
+and lzip files only: 'zgrep foo -r --format=gz,lz somedir somefile.tar'.
 
    FORMAT NOTE 2: If the option '--force-format' is given, the files are
 passed to the corresponding decompressor without verifying their format,
@@ -110,12 +112,14 @@ here. *Note Argument syntax: (arg_parser)Argument syntax.
 '-V'
 '--version'
      Print the version number on the standard output and exit. This version
-     number should be included in all bug reports.
+     number should be included in all bug reports. In verbose mode, zdiff
+     and zgrep print also the version of the diff or grep program used
+     respectively.
 
 '-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
+     Valid formats are 'bz2', 'gz', 'lz', 'xz', 'zst', 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
@@ -130,6 +134,7 @@ here. *Note Argument syntax: (arg_parser)Argument syntax.
      gz    enables   .gz .tgz
      lz    enables   .lz .tlz
      xz    enables   .xz .txz
+     zst   enables   .zst .tzst
      un    enables   any other file name
 
 '-N'
@@ -140,17 +145,18 @@ here. *Note Argument syntax: (arg_parser)Argument syntax.
 '--gz=COMMAND'
 '--lz=COMMAND'
 '--xz=COMMAND'
+'--zst=COMMAND'
      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
+     decompression. The others 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 option '-d', it must read compressed data
-          from the standard input and produce decompressed data on the
-          standard output.
+       1. When called with the option '-d' and without file names, it must
+          read compressed data from the standard input and produce
+          decompressed data on the standard output.
 
        2. If the option '-q' is passed to zutils, the compression program
           must also accept it.
@@ -181,7 +187,7 @@ is fairly obvious (and there are further instructions in it):
   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', 'xz', or 'zst'.
 
 
 File: zutils.info,  Node: Zcat,  Next: Zcmp,  Prev: The zutilsrc file,  Up: Top
@@ -235,9 +241,10 @@ Exit status is 0 if no errors occurred, 1 otherwise.
 '-O FORMAT'
 '--force-format=FORMAT'
      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.
+     'gz', 'lz', 'xz', and 'zst'. 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'
@@ -301,7 +308,7 @@ following:
      removed).
 
    - If FILE1 is uncompressed, compares it with the decompressed contents
-     of FILE1.[lz|bz2|gz|xz] (the first one that is found).
+     of FILE1.[lz|bz2|gz|zst|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.
@@ -336,11 +343,11 @@ differences were found, and 2 means trouble.
 '--force-format=[FORMAT1][,FORMAT2]'
      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.
+     Valid values for FORMAT are 'bz2', 'gz', 'lz', 'xz', and 'zst'. 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'
@@ -376,7 +383,7 @@ following:
      removed).
 
    - If FILE1 is uncompressed, compares it with the decompressed contents
-     of FILE1.[lz|bz2|gz|xz] (the first one that is found).
+     of FILE1.[lz|bz2|gz|zst|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.
@@ -419,11 +426,11 @@ program used supports them):
 '--force-format=[FORMAT1][,FORMAT2]'
      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.
+     Valid values for FORMAT are 'bz2', 'gz', 'lz', 'xz', and 'zst'. 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'
@@ -452,6 +459,11 @@ program used supports them):
 '--unified=N'
      Same as -u but use N lines of context.
 
+'-v'
+'--verbose'
+     When specified before '--version', print the version of the diff
+     program used.
+
 '-w'
 '--ignore-all-space'
      Ignore all white space.
@@ -576,9 +588,10 @@ program used supports them):
 '-O FORMAT'
 '--force-format=FORMAT'
      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.
+     'gz', 'lz', 'xz', and 'zst'. 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'
@@ -605,7 +618,8 @@ program used supports them):
      Select non-matching lines.
 
 '--verbose'
-     Verbose mode. Show error messages.
+     Verbose mode. Show error messages. When specified before '--version',
+     print the version of the grep program used.
 
 '-w'
 '--word-regexp'
@@ -634,6 +648,10 @@ test when testing multiple files.
    If no files are specified, recursive searches examine the current working
 directory, and nonrecursive searches read standard input.
 
+   Bzip2, gzip, and lzip are the primary formats. Xz and zstd are optional.
+If the decompressor for the xz or zstd formats is not found, the
+corresponding files are ignored.
+
    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'
@@ -654,11 +672,12 @@ compressed file is corrupt or invalid.
 '-O FORMAT'
 '--force-format=FORMAT'
      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.
+     'gz', 'lz', 'xz', and 'zst'. 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'
@@ -687,14 +706,14 @@ 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, xz, and zstd 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.
@@ -706,17 +725,26 @@ 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.
 
+   Recompressing files from a read-only file system to another place can be
+done by first linking the files from the destination directory and then
+compressing the links: 'ln -s /src/foo.gz . && zupdate foo.gz'
+
    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', '.gz', or '.xz', which are recompressed to '.lz';
-'.tbz', '.tbz2', '.tgz', or '.txz', which are recompressed to '.tlz'.
+'.bz2', '.gz', '.xz', or '.zst', which are recompressed to '.lz';
+'.tbz', '.tbz2', '.tgz', '.txz', or '.tzst', which are recompressed to
+'.tlz'.
 Keeping the combined extensions ('.tgz' -> '.tlz') may be useful when
 recompressing Slackware packages, for example.
 
+   Bzip2, gzip, and lzip are the primary formats. Xz and zstd are optional.
+If the decompressor for the xz or zstd formats is not found, the
+corresponding files are ignored.
+
    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
@@ -816,19 +844,19 @@ Concept index
 
 
 Tag Table:
-Node: Top222
-Node: Introduction1151
-Node: Common options3776
-Ref: compressor-requirements5847
-Node: The zutilsrc file6219
-Node: Zcat7180
-Node: Zcmp9743
-Node: Zdiff12233
-Node: Zgrep14973
-Node: Ztest19218
-Node: Zupdate21725
-Node: Problems25409
-Node: Concept index25943
+Node: Top217
+Node: Introduction1147
+Node: Common options3947
+Ref: compressor-requirements6181
+Node: The zutilsrc file6576
+Node: Zcat7544
+Node: Zcmp10119
+Node: Zdiff12620
+Node: Zgrep15478
+Node: Ztest19819
+Node: Zupdate22513
+Node: Problems26607
+Node: Concept index27141
 
 End Tag Table
 
diff --git a/doc/zutils.texi b/doc/zutils.texi
index c494185..34a3128 100644
--- a/doc/zutils.texi
+++ b/doc/zutils.texi
@@ -6,10 +6,10 @@
 @finalout
 @c %**end of header
 
-@set UPDATED 5 January 2021
-@set VERSION 1.10
+@set UPDATED 25 January 2022
+@set VERSION 1.11
 
-@dircategory Data Compression
+@dircategory Compression
 @direntry
 * Zutils: (zutils).             Utilities dealing with compressed files
 @end direntry
@@ -50,7 +50,7 @@ This manual is for Zutils (version @value{VERSION}, @value{UPDATED}).
 @end menu
 
 @sp 1
-Copyright @copyright{} 2009-2021 Antonio Diaz Diaz.
+Copyright @copyright{} 2009-2022 Antonio Diaz Diaz.
 
 This manual is free documentation: you have unlimited permission to copy,
 distribute, and modify it.
@@ -74,7 +74,7 @@ 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.@*
+The formats supported are bzip2, gzip, lzip, xz, and zstd.@*
 Zutils uses external compressors. The compressor to be used for each format
 is configurable at runtime.
 
@@ -84,12 +84,15 @@ 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.
+values, making them less reliable back ends for zutils. Zstd currently does
+not even document its exit status in its man page.
 @xref{compressor-requirements}.
 
 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}}.
+of formats in recursive mode and when trying compressed file names. For
+example, use the following command to search for the string @samp{foo} in
+gzip and lzip files only:
+@w{@samp{zgrep foo -r --format=gz,lz somedir somefile.tar}}.
 
 FORMAT NOTE 2: If the option @samp{--force-format} is given, the files are
 passed to the corresponding decompressor without verifying their format,
@@ -141,17 +144,19 @@ only supports the @samp{--help} form of this option.
 @itemx --version
 Print the version number on the standard output and exit.
 This version number should be included in all bug reports.
+In verbose mode, zdiff and zgrep print also the version of the diff or grep
+program used respectively.
 
 @item -M @var{format_list}
 @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
-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 @var{format_list}.
+Valid formats are @samp{bz2}, @samp{gz}, @samp{lz}, @samp{xz}, @samp{zst},
+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 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 @var{format_list} enables file names with the following
 extensions:
@@ -161,6 +166,7 @@ extensions:
 @item gz  @tab enables @tab .gz .tgz
 @item lz  @tab enables @tab .lz .tlz
 @item xz  @tab enables @tab .xz .txz
+@item zst @tab enables @tab .zst .tzst
 @item un  @tab enables @tab any other file name
 @end multitable
 
@@ -172,19 +178,21 @@ Don't read the runtime configuration file @samp{zutilsrc}.
 @itemx --gz=@var{command}
 @itemx --lz=@var{command}
 @itemx --xz=@var{command}
+@itemx --zst=@var{command}
 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
+used for both compression and decompression. The others 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 option @samp{-d}, it must read compressed data from
-the standard input and produce decompressed data on the standard output.
+When called with the option @samp{-d} and without file names, it must read
+compressed data from the standard input and produce decompressed data on the
+standard output.
 @item
 If the option @samp{-q} is passed to zutils, the compression program must
 also accept it.
@@ -220,7 +228,8 @@ 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}, @samp{xz}, or
+@samp{zst}.
 @end enumerate
 
 
@@ -278,10 +287,10 @@ Number all output lines, starting with 1. The line count is unlimited.
 @item -O @var{format}
 @itemx --force-format=@var{format}
 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.
+@samp{bz2}, @samp{gz}, @samp{lz}, @samp{xz}, and @samp{zst}. 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.
 
 @item -q
 @itemx --quiet
@@ -350,7 +359,7 @@ the corresponding uncompressed file (the name of @var{file1} with the
 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).
+contents of @var{file1}.[lz|bz2|gz|zst|xz] (the first one that is found).
 @end itemize
 
 @noindent
@@ -387,13 +396,13 @@ Compare at most @var{count} input bytes.
 
 @item -O [@var{format1}][,@var{format2}]
 @itemx --force-format=[@var{format1}][,@var{format2}]
-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
-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.
+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},
+@samp{xz}, and @samp{zst}. 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.
 
 @item -q
 @itemx -s
@@ -434,7 +443,7 @@ the corresponding uncompressed file (the name of @var{file1} with the
 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).
+contents of @var{file1}.[lz|bz2|gz|zst|xz] (the first one that is found).
 @end itemize
 
 @noindent
@@ -478,13 +487,13 @@ Ignore case differences in file contents.
 
 @item -O [@var{format1}][,@var{format2}]
 @itemx --force-format=[@var{format1}][,@var{format2}]
-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
-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.
+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},
+@samp{xz}, and @samp{zst}. 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.
 
 @item -p
 @itemx --show-c-function
@@ -513,6 +522,11 @@ Use the unified output format.
 @itemx --unified=@var{n}
 Same as -u but use @var{n} lines of context.
 
+@item -v
+@itemx --verbose
+When specified before @samp{--version}, print the version of the diff
+program used.
+
 @item -w
 @itemx --ignore-all-space
 Ignore all white space.
@@ -644,10 +658,10 @@ Show only the part of matching lines that actually matches @var{pattern}.
 @item -O @var{format}
 @itemx --force-format=@var{format}
 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.
+@samp{bz2}, @samp{gz}, @samp{lz}, @samp{xz}, and @samp{zst}. 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.
 
 @item -q
 @itemx --quiet
@@ -674,7 +688,8 @@ Suppress error messages about nonexistent or unreadable files.
 Select non-matching lines.
 
 @item --verbose
-Verbose mode. Show error messages.
+Verbose mode. Show error messages. When specified before @samp{--version},
+print the version of the grep program used.
 
 @item -w
 @itemx --word-regexp
@@ -703,6 +718,10 @@ test when testing multiple files.
 If no files are specified, recursive searches examine the current working
 directory, and nonrecursive searches read standard input.
 
+Bzip2, gzip, and lzip are the primary formats. Xz and zstd are optional. If
+the decompressor for the xz or zstd formats is not found, the corresponding
+files are ignored.
+
 Note that error detection in the xz format is broken. First, some xz
 files lack integrity information. Second, not all xz decompressors can
 @uref{http://www.nongnu.org/lzip/xz_inadequate.html#fragmented,,verify the integrity}
@@ -730,11 +749,11 @@ ztest supports the following options:
 @item -O @var{format}
 @itemx --force-format=@var{format}
 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.
+@samp{bz2}, @samp{gz}, @samp{lz}, @samp{xz}, and @samp{zst}. 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
@@ -763,14 +782,14 @@ 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, xz, and zstd 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.
@@ -782,21 +801,29 @@ 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.
 
+Recompressing files from a read-only file system to another place can be
+done by first linking the files from the destination directory and then
+compressing the links: @w{@samp{ln -s /src/foo.gz . && zupdate foo.gz}}
+
 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{.gz}, or @samp{.xz}, which are recompressed to
-@samp{.lz};@*
-@samp{.tbz}, @samp{.tbz2}, @samp{.tgz}, or @samp{.txz}, which are
-recompressed to @samp{.tlz}.@*
+@samp{.bz2}, @samp{.gz}, @samp{.xz}, or @samp{.zst}, which are recompressed
+to @samp{.lz};@*
+@samp{.tbz}, @samp{.tbz2}, @samp{.tgz}, @samp{.txz}, or @samp{.tzst}, which
+are recompressed to @samp{.tlz}.@*
 Keeping the combined extensions (@samp{.tgz} --> @samp{.tlz}) may be useful
 when recompressing Slackware packages, for example.
 
+Bzip2, gzip, and lzip are the primary formats. Xz and zstd are optional. If
+the decompressor for the xz or zstd formats is not found, the corresponding
+files are ignored.
+
 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
+possible, ownership of the file just as @w{@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).