Merging upstream version 1.6~pre1.

Signed-off-by: Daniel Baumann <mail@daniel-baumann.ch>

3 files changed, 177 insertions, 156 deletions

diff --git a/doc/clzip.1 b/doc/clzip.1
index a365d55..7be6a38 100644
--- a/doc/clzip.1
+++ b/doc/clzip.1
@@ -1,5 +1,5 @@
 .\" DO NOT MODIFY THIS FILE!  It was generated by help2man 1.37.1.
-.TH CLZIP "1" "September 2013" "Clzip 1.5" "User Commands"
+.TH CLZIP "1" "January 2014" "Clzip 1.6-pre1" "User Commands"
 .SH NAME
 Clzip \- reduces the size of files
 .SH SYNOPSIS
@@ -82,7 +82,7 @@ Report bugs to lzip\-bug@nongnu.org
 .br
 Clzip home page: http://www.nongnu.org/lzip/clzip.html
 .SH COPYRIGHT
-Copyright \(co 2013 Antonio Diaz Diaz.
+Copyright \(co 2014 Antonio Diaz Diaz.
 License GPLv3+: GNU GPL version 3 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/clzip.info b/doc/clzip.info
index 227a396..1819221 100644
--- a/doc/clzip.info
+++ b/doc/clzip.info
@@ -1,5 +1,4 @@
-This is clzip.info, produced by makeinfo version 4.13 from
-clzip.texinfo.
+This is clzip.info, produced by makeinfo version 4.13+ from clzip.texi.
 
 INFO-DIR-SECTION Data Compression
 START-INFO-DIR-ENTRY
@@ -12,7 +11,7 @@ File: clzip.info,  Node: Top,  Next: Introduction,  Up: (dir)
 Clzip Manual
 ************
 
-This manual is for Clzip (version 1.5, 17 September 2013).
+This manual is for Clzip (version 1.6-pre1, 30 January 2014).
 
 * Menu:
 
@@ -25,7 +24,7 @@ This manual is for Clzip (version 1.5, 17 September 2013).
 * Concept index::          Index of concepts
 
 
-   Copyright (C) 2010, 2011, 2012, 2013 Antonio Diaz Diaz.
+   Copyright (C) 2010, 2011, 2012, 2013, 2014 Antonio Diaz Diaz.
 
    This manual is free documentation: you have unlimited permission to
 copy, distribute and modify it.
@@ -37,10 +36,10 @@ File: clzip.info,  Node: Introduction,  Next: Algorithm,  Prev: Top,  Up: Top
 **************
 
 Clzip is a lossless data compressor with a user interface similar to the
-one of gzip or bzip2. Clzip decompresses almost as fast as gzip and
-compresses more than bzip2, which makes it well suited for software
-distribution and data archiving. Clzip is a clean implementation of the
-LZMA algorithm.
+one of gzip or bzip2. Clzip decompresses almost as fast as gzip,
+compresses most files more than bzip2, and is better than both from a
+data recovery perspective. Clzip is a clean implementation of the LZMA
+algorithm.
 
    Clzip uses the lzip file format; the files produced by clzip are
 fully compatible with lzip-1.4 or newer, and can be rescued with
@@ -48,17 +47,24 @@ lziprecover.  Clzip is in fact a C language version of lzip, intended
 for embedded devices or systems lacking a C++ compiler.
 
    The lzip file format is designed for long-term data archiving and
-provides very safe integrity checking. The member trailer stores the
-32-bit CRC of the original data, the size of the original data and the
-size of the member. These values, together with the value remaining in
-the range decoder and the end-of-stream marker, provide a 4 factor
-integrity checking which guarantees that the decompressed version of the
-data is identical to the original. This guards against corruption of the
-compressed data, and against undetected bugs in clzip (hopefully very
-unlikely). The chances of data corruption going undetected are
-microscopic. Be aware, though, that the check occurs upon decompression,
-so it can only tell you that something is wrong. It can't help you
-recover the original uncompressed data.
+provides very safe integrity checking. It is as simple as possible (but
+not simpler), so that with the only help of the lzip manual it would be
+possible for a digital archaeologist to extract the data from a lzip
+file long after quantum computers eventually render LZMA obsolete.
+Additionally lzip is copylefted, which guarantees that it will remain
+free forever.
+
+   The member trailer stores the 32-bit CRC of the original data, the
+size of the original data and the size of the member. These values,
+together with the value remaining in the range decoder and the
+end-of-stream marker, provide a 4 factor integrity checking which
+guarantees that the decompressed version of the data is identical to
+the original. This guards against corruption of the compressed data,
+and against undetected bugs in clzip (hopefully very unlikely). The
+chances of data corruption going undetected are microscopic. Be aware,
+though, that the check occurs upon decompression, so it can only tell
+you that something is wrong. It can't help you recover the original
+uncompressed data.
 
    If you ever need to recover data from a damaged lzip file, try the
 lziprecover program. Lziprecover makes lzip files resistant to bit-flip
@@ -67,15 +73,26 @@ recovery capabilities, including error-checked merging of damaged copies
 of a file.
 
    Clzip uses the same well-defined exit status values used by lzip and
-bzip2, which makes it safer when used in pipes or scripts than
-compressors returning ambiguous warning values, like gzip.
+bzip2, which makes it safer than compressors returning ambiguous warning
+values (like gzip) when it is used as a back end for tar or zutils.
 
-   Clzip replaces every file given in the command line with a compressed
-version of itself, with the name "original_name.lz". Each compressed
-file has the same modification date, permissions, and, when possible,
-ownership as the corresponding original, so that these properties can be
-correctly restored at decompression time. Clzip is able to read from
-some types of non regular files if the `--stdout' option is specified.
+   When compressing, clzip replaces every file given in the command line
+with a compressed version of itself, with the name "original_name.lz".
+When decompressing, clzip attempts to guess the name for the
+decompressed file from that of the compressed file as follows:
+
+filename.lz    becomes   filename
+filename.tlz   becomes   filename.tar
+anyothername   becomes   anyothername.out
+
+   (De)compressing a file is much like copying or moving it; therefore
+clzip 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).
+
+   Clzip is able to read from some types of non regular files if the
+'--stdout' option is specified.
 
    If no file names are specified, clzip compresses (or decompresses)
 from standard input to standard output. In this case, clzip will
@@ -100,21 +117,14 @@ large, about 64 PiB each.
    The amount of memory required for compression is about 1 or 2 times
 the dictionary size limit (1 if input file size is less than dictionary
 size limit, else 2) plus 9 times the dictionary size really used. The
-amount of memory required for decompression is only a few tens of KiB
-larger than the dictionary size really used.
+amount of memory required for decompression is about 46 kB larger than
+the dictionary size really used.
 
    Clzip will automatically use the smallest possible dictionary size
 without exceeding the given limit. Keep in mind that the decompression
 memory requirement is affected at compression time by the choice of
 dictionary size limit.
 
-   When decompressing, clzip attempts to guess the name for the
-decompressed file from that of the compressed file as follows:
-
-filename.lz    becomes   filename
-filename.tlz   becomes   filename.tar
-anyothername   becomes   anyothername.out
-
 
 File: clzip.info,  Node: Algorithm,  Next: Invoking clzip,  Prev: Introduction,  Up: Top
 
@@ -160,7 +170,7 @@ price represents the number of output bits produced.
    6) The range encoder encodes the sequence produced by the main
 encoder and sends the produced bytes to the output stream.
 
-   7) Go back to step 3 until the input data is finished or until the
+   7) Go back to step 3 until the input data are finished or until the
 member or volume size limits are reached.
 
    8) The range encoder is flushed.
@@ -188,67 +198,67 @@ The format for running clzip is:
 
    Clzip supports the following options:
 
-`-h'
-`--help'
+'-h'
+'--help'
      Print an informative help message describing the options and exit.
 
-`-V'
-`--version'
+'-V'
+'--version'
      Print the version number of clzip on the standard output and exit.
 
-`-b BYTES'
-`--member-size=BYTES'
+'-b BYTES'
+'--member-size=BYTES'
      Set the member size limit to BYTES. A small member size may
      degrade compression ratio, so use it only when needed. Valid values
      range from 100 kB to 64 PiB. Defaults to 64 PiB.
 
-`-c'
-`--stdout'
+'-c'
+'--stdout'
      Compress or decompress to standard output. Needed when reading
      from a named pipe (fifo) or from a device. Use it to recover as
      much of the uncompressed data as possible when decompressing a
      corrupt file.
 
-`-d'
-`--decompress'
+'-d'
+'--decompress'
      Decompress.
 
-`-f'
-`--force'
+'-f'
+'--force'
      Force overwrite of output files.
 
-`-F'
-`--recompress'
-     Force recompression of files whose name already has the `.lz' or
-     `.tlz' suffix.
+'-F'
+'--recompress'
+     Force recompression of files whose name already has the '.lz' or
+     '.tlz' suffix.
 
-`-k'
-`--keep'
+'-k'
+'--keep'
      Keep (don't delete) input files during compression or
      decompression.
 
-`-m BYTES'
-`--match-length=BYTES'
+'-m BYTES'
+'--match-length=BYTES'
      Set the match length limit in bytes. After a match this long is
      found, the search is finished. Valid values range from 5 to 273.
      Larger values usually give better compression ratios but longer
      compression times.
 
-`-o FILE'
-`--output=FILE'
-     When reading from standard input and `--stdout' has not been
-     specified, use `FILE' as the virtual name of the uncompressed
-     file. This produces a file named `FILE' when decompressing, a file
-     named `FILE.lz' when compressing, and several files named
-     `FILE00001.lz', `FILE00002.lz', etc, when compressing and
+'-o FILE'
+'--output=FILE'
+     When reading from standard input and '--stdout' has not been
+     specified, use 'FILE' as the virtual name of the uncompressed
+     file. This produces a file named 'FILE' when decompressing, a file
+     named 'FILE.lz' when compressing, and several files named
+     'FILE00001.lz', 'FILE00002.lz', etc, when compressing and
      splitting the output in volumes.
 
-`-q'
-`--quiet'
+'-q'
+'--quiet'
      Quiet operation. Suppress all messages.
 
-`-s BYTES'
-`--dictionary-size=BYTES'
+'-s BYTES'
+'--dictionary-size=BYTES'
      Set the dictionary size limit in bytes. Valid values range from 4
      KiB to 512 MiB. Clzip will use the smallest possible dictionary
      size for each member without exceeding this limit. Note that
@@ -261,42 +271,42 @@ The format for running clzip is:
      requirement is affected at compression time by the choice of
      dictionary size limit.
 
-`-S BYTES'
-`--volume-size=BYTES'
+'-S BYTES'
+'--volume-size=BYTES'
      Split the compressed output into several volume files with names
-     `original_name00001.lz', `original_name00002.lz', etc, and set the
+     'original_name00001.lz', 'original_name00002.lz', etc, and set the
      volume size limit to BYTES. Each volume is a complete, maybe
      multi-member, lzip file. A small volume size may degrade
      compression ratio, so use it only when needed. Valid values range
      from 100 kB to 4 EiB.
 
-`-t'
-`--test'
+'-t'
+'--test'
      Check integrity of the specified file(s), but don't decompress
      them.  This really performs a trial decompression and throws away
-     the result.  Use it together with `-v' to see information about
+     the result.  Use it together with '-v' to see information about
      the file.
 
-`-v'
-`--verbose'
+'-v'
+'--verbose'
      Verbose mode.
      When compressing, show the compression ratio for each file
-     processed. A second `-v' shows the progress of compression.
+     processed. A second '-v' shows the progress of compression.
      When decompressing or testing, further -v's (up to 4) increase the
      verbosity level, showing status, compression ratio, dictionary
      size, and trailer contents (CRC, data size, member size).
 
-`-1 .. -9'
+'-1 .. -9'
      Set the compression parameters (dictionary size and match length
-     limit) as shown in the table below. Note that `-9' can be much
-     slower than `-1'. These options have no effect when decompressing.
+     limit) as shown in the table below. Note that '-9' can be much
+     slower than '-1'. These options have no effect when decompressing.
 
      The bidimensional parameter space of LZMA can't be mapped to a
      linear scale optimal for all files. If your files are large, very
-     repetitive, etc, you may need to use the `--match-length' and
-     `--dictionary-size' options directly to achieve optimal
-     performance. For example, `-9m64' usually compresses executables
-     more (and faster) than `-9'.
+     repetitive, etc, you may need to use the '--match-length' and
+     '--dictionary-size' options directly to achieve optimal
+     performance. For example, '-9m64' usually compresses executables
+     more (and faster) than '-9'.
 
      Level   Dictionary size   Match length limit
      -1      1 MiB             5 bytes
@@ -309,13 +319,13 @@ The format for running clzip is:
      -8      24 MiB            132 bytes
      -9      32 MiB            273 bytes
 
-`--fast'
-`--best'
+'--fast'
+'--best'
      Aliases for GNU gzip compatibility.
 
 
    Numbers given as arguments to options may be followed by a multiplier
-and an optional `B' for "byte".
+and an optional 'B' for "byte".
 
    Table of SI and binary prefixes (unit multipliers):
 
@@ -370,15 +380,15 @@ additional information before, between, or after them.
 
    All multibyte values are stored in little endian order.
 
-`ID string'
+'ID string'
      A four byte string, identifying the lzip format, with the value
      "LZIP" (0x4C, 0x5A, 0x49, 0x50).
 
-`VN (version number, 1 byte)'
+'VN (version number, 1 byte)'
      Just in case something needs to be modified in the future. 1 for
      now.
 
-`DS (coded dictionary size, 1 byte)'
+'DS (coded dictionary size, 1 byte)'
      Lzip divides the distance between any two powers of 2 into 8
      equally spaced intervals, named "wedges". The dictionary size is
      calculated by taking a power of 2 (the base size) and substracting
@@ -390,18 +400,18 @@ additional information before, between, or after them.
      Example: 0xD3 = 2^19 - 6 * 2^15 = 512 KiB - 6 * 32 KiB = 320 KiB
      Valid values for dictionary size range from 4 KiB to 512 MiB.
 
-`Lzma stream'
+'Lzma stream'
      The lzma stream, finished by an end of stream marker. Uses default
      values for encoder properties. See the lzip manual for a full
      description.
 
-`CRC32 (4 bytes)'
+'CRC32 (4 bytes)'
      CRC of the uncompressed original data.
 
-`Data size (8 bytes)'
+'Data size (8 bytes)'
      Size of the uncompressed original data.
 
-`Member size (8 bytes)'
+'Member size (8 bytes)'
      Total size of the member, including header and trailer. This field
      acts as a distributed index, allows the verification of stream
      integrity, and facilitates safe recovery of undamaged members from
@@ -416,49 +426,49 @@ File: clzip.info,  Node: Examples,  Next: Problems,  Prev: File format,  Up: Top
 
 WARNING! Even if clzip is bug-free, other causes may result in a corrupt
 compressed file (bugs in the system libraries, memory errors, etc).
-Therefore, if the data you are going to compress is important, give the
-`--keep' option to clzip and do not remove the original file until you
+Therefore, if the data you are going to compress are important, give the
+'--keep' option to clzip and do not remove the original file until you
 verify the compressed file with a command like
-`clzip -cd file.lz | cmp file -'.
+'clzip -cd file.lz | cmp file -'.
 
 
-Example 1: Replace a regular file with its compressed version `file.lz'
+Example 1: Replace a regular file with its compressed version 'file.lz'
 and show the compression ratio.
 
      clzip -v file
 
 
-Example 2: Like example 1 but the created `file.lz' is multi-member
+Example 2: Like example 1 but the created 'file.lz' is multi-member
 with a member size of 1 MiB. The compression ratio is not shown.
 
      clzip -b 1MiB file
 
 
 Example 3: Restore a regular file from its compressed version
-`file.lz'. If the operation is successful, `file.lz' is removed.
+'file.lz'. If the operation is successful, 'file.lz' is removed.
 
      clzip -d file.lz
 
 
-Example 4: Verify the integrity of the compressed file `file.lz' and
+Example 4: Verify the integrity of the compressed file 'file.lz' and
 show status.
 
      clzip -tv file.lz
 
 
 Example 5: Compress a whole floppy in /dev/fd0 and send the output to
-`file.lz'.
+'file.lz'.
 
      clzip -c /dev/fd0 > file.lz
 
 
-Example 6: Decompress `file.lz' partially until 10 KiB of decompressed
+Example 6: Decompress 'file.lz' partially until 10 KiB of decompressed
 data are produced.
 
      clzip -cd file.lz | dd bs=1024 count=10
 
 
-Example 7: Decompress `file.lz' partially from decompressed byte 10000
+Example 7: Decompress 'file.lz' partially from decompressed byte 10000
 to decompressed byte 15000 (5000 bytes are produced).
 
      clzip -cd file.lz | dd bs=1000 skip=10 count=5
@@ -494,7 +504,7 @@ for all eternity, if not longer.
 
    If you find a bug in clzip, please send electronic mail to
 <lzip-bug@nongnu.org>. Include the version number, which you can find
-by running `clzip --version'.
+by running 'clzip --version'.
 
 
 File: clzip.info,  Node: Concept index,  Prev: Problems,  Up: Top
@@ -519,14 +529,14 @@ Concept index
 
 
 Tag Table:
-Node: Top212
-Node: Introduction914
-Node: Algorithm5091
-Node: Invoking clzip7590
-Node: File format13189
-Node: Examples15694
-Node: Problems17662
-Node: Concept index18188
+Node: Top210
+Node: Introduction921
+Node: Algorithm5557
+Node: Invoking clzip8057
+Node: File format13656
+Node: Examples16161
+Node: Problems18130
+Node: Concept index18656
 
 End Tag Table
 
diff --git a/doc/clzip.texinfo b/doc/clzip.texi
index 95bfe68..25869a0 100644
--- a/doc/clzip.texinfo
+++ b/doc/clzip.texi
@@ -6,8 +6,8 @@
 @finalout
 @c %**end of header
 
-@set UPDATED 17 September 2013
-@set VERSION 1.5
+@set UPDATED 30 January 2014
+@set VERSION 1.6-pre1
 
 @dircategory Data Compression
 @direntry
@@ -45,7 +45,7 @@ This manual is for Clzip (version @value{VERSION}, @value{UPDATED}).
 @end menu
 
 @sp 1
-Copyright @copyright{} 2010, 2011, 2012, 2013 Antonio Diaz Diaz.
+Copyright @copyright{} 2010, 2011, 2012, 2013, 2014 Antonio Diaz Diaz.
 
 This manual is free documentation: you have unlimited permission
 to copy, distribute and modify it.
@@ -56,10 +56,10 @@ to copy, distribute and modify it.
 @cindex introduction
 
 Clzip is a lossless data compressor with a user interface similar to the
-one of gzip or bzip2. Clzip decompresses almost as fast as gzip and
-compresses more than bzip2, which makes it well suited for software
-distribution and data archiving. Clzip is a clean implementation of the
-LZMA algorithm.
+one of gzip or bzip2. Clzip decompresses almost as fast as gzip,
+compresses most files more than bzip2, and is better than both from a
+data recovery perspective. Clzip is a clean implementation of the LZMA
+algorithm.
 
 Clzip uses the lzip file format; the files produced by clzip are fully
 compatible with lzip-1.4 or newer, and can be rescued with lziprecover.
@@ -67,17 +67,23 @@ Clzip is in fact a C language version of lzip, intended for embedded
 devices or systems lacking a C++ compiler.
 
 The lzip file format is designed for long-term data archiving and
-provides very safe integrity checking. The member trailer stores the
-32-bit CRC of the original data, the size of the original data and the
-size of the member. These values, together with the value remaining in
-the range decoder and the end-of-stream marker, provide a 4 factor
-integrity checking which guarantees that the decompressed version of the
-data is identical to the original. This guards against corruption of the
-compressed data, and against undetected bugs in clzip (hopefully very
-unlikely). The chances of data corruption going undetected are
-microscopic. Be aware, though, that the check occurs upon decompression,
-so it can only tell you that something is wrong. It can't help you
-recover the original uncompressed data.
+provides very safe integrity checking. It is as simple as possible (but
+not simpler), so that with the only help of the lzip manual it would be
+possible for a digital archaeologist to extract the data from a lzip
+file long after quantum computers eventually render LZMA obsolete.
+Additionally lzip is copylefted, which guarantees that it will remain
+free forever.
+
+The member trailer stores the 32-bit CRC of the original data, the size
+of the original data and the size of the member. These values, together
+with the value remaining in the range decoder and the end-of-stream
+marker, provide a 4 factor integrity checking which guarantees that the
+decompressed version of the data is identical to the original. This
+guards against corruption of the compressed data, and against undetected
+bugs in clzip (hopefully very unlikely). The chances of data corruption
+going undetected are microscopic. Be aware, though, that the check
+occurs upon decompression, so it can only tell you that something is
+wrong. It can't help you recover the original uncompressed data.
 
 If you ever need to recover data from a damaged lzip file, try the
 lziprecover program. Lziprecover makes lzip files resistant to bit-flip
@@ -86,15 +92,28 @@ recovery capabilities, including error-checked merging of damaged copies
 of a file.
 
 Clzip uses the same well-defined exit status values used by lzip and
-bzip2, which makes it safer when used in pipes or scripts than
-compressors returning ambiguous warning values, like gzip.
+bzip2, which makes it safer than compressors returning ambiguous warning
+values (like gzip) when it is used as a back end for tar or zutils.
 
-Clzip replaces every file given in the command line with a compressed
-version of itself, with the name "original_name.lz". Each compressed
-file has the same modification date, permissions, and, when possible,
-ownership as the corresponding original, so that these properties can be
-correctly restored at decompression time. Clzip is able to read from some
-types of non regular files if the @samp{--stdout} option is specified.
+When compressing, clzip replaces every file given in the command line
+with a compressed version of itself, with the name "original_name.lz".
+When decompressing, clzip attempts to guess the name for the decompressed
+file from that of the compressed file as follows:
+
+@multitable {anyothername} {becomes} {anyothername.out}
+@item filename.lz  @tab becomes @tab filename
+@item filename.tlz @tab becomes @tab filename.tar
+@item anyothername @tab becomes @tab anyothername.out
+@end multitable
+
+(De)compressing a file is much like copying or moving it; therefore clzip
+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).
+
+Clzip is able to read from some types of non regular files if the
+@samp{--stdout} option is specified.
 
 If no file names are specified, clzip compresses (or decompresses) from
 standard input to standard output. In this case, clzip will decline to
@@ -119,23 +138,14 @@ large, about 64 PiB each.
 The amount of memory required for compression is about 1 or 2 times the
 dictionary size limit (1 if input file size is less than dictionary size
 limit, else 2) plus 9 times the dictionary size really used. The amount
-of memory required for decompression is only a few tens of KiB larger
-than the dictionary size really used.
+of memory required for decompression is about 46 kB larger than the
+dictionary size really used.
 
 Clzip will automatically use the smallest possible dictionary size
 without exceeding the given limit. Keep in mind that the decompression
 memory requirement is affected at compression time by the choice of
 dictionary size limit.
 
-When decompressing, clzip attempts to guess the name for the decompressed
-file from that of the compressed file as follows:
-
-@multitable {anyothername} {becomes} {anyothername.out}
-@item filename.lz  @tab becomes @tab filename
-@item filename.tlz @tab becomes @tab filename.tar
-@item anyothername @tab becomes @tab anyothername.out
-@end multitable
-
 
 @node Algorithm
 @chapter Algorithm
@@ -180,7 +190,7 @@ price represents the number of output bits produced.
 6) The range encoder encodes the sequence produced by the main encoder
 and sends the produced bytes to the output stream.
 
-7) Go back to step 3 until the input data is finished or until the
+7) Go back to step 3 until the input data are finished or until the
 member or volume size limits are reached.
 
 8) The range encoder is flushed.
@@ -420,8 +430,9 @@ Example: 0xD3 = 2^19 - 6 * 2^15 = 512 KiB - 6 * 32 KiB = 320 KiB@*
 Valid values for dictionary size range from 4 KiB to 512 MiB.
 
 @item Lzma stream
-The lzma stream, finished by an end of stream marker. Uses default values
-for encoder properties. See the lzip manual for a full description.
+The lzma stream, finished by an end of stream marker. Uses default
+values for encoder properties. See the lzip manual for a full
+description.
 
 @item CRC32 (4 bytes)
 CRC of the uncompressed original data.
@@ -443,7 +454,7 @@ facilitates safe recovery of undamaged members from multi-member files.
 
 WARNING! Even if clzip is bug-free, other causes may result in a corrupt
 compressed file (bugs in the system libraries, memory errors, etc).
-Therefore, if the data you are going to compress is important, give the
+Therefore, if the data you are going to compress are important, give the
 @samp{--keep} option to clzip and do not remove the original file until
 you verify the compressed file with a command like
 @w{@samp{clzip -cd file.lz | cmp file -}}.