X-Git-Url: https://git.gag.com/?a=blobdiff_plain;f=doc%2Fgzip.texi;fp=doc%2Fgzip.texi;h=c7f8d62ad94c338c02e09b95468663c169f17c59;hb=800deb09b422a73c1212233a93839a223ff59678;hp=9be2aa38d3d5d8d4a2c2501662dceff9094eeef9;hpb=0d5a754ba8f2cc33e98d48d559f0ad6cd18a43a3;p=debian%2Fgzip diff --git a/doc/gzip.texi b/doc/gzip.texi index 9be2aa3..c7f8d62 100644 --- a/doc/gzip.texi +++ b/doc/gzip.texi @@ -11,8 +11,8 @@ This manual is for Gzip (version @value{VERSION}, @value{UPDATED}), and documents commands for compressing and decompressing data. -Copyright @copyright{} 1998, 1999, 2001, 2002, 2006 Free Software -Foundation, Inc. +Copyright @copyright{} 1998, 1999, 2001, 2002, 2006, 2007 Free +Software Foundation, Inc. Copyright @copyright{} 1992, 1993 Jean-loup Gailly @@ -27,15 +27,17 @@ Free Documentation License''. @end copying @c Debian install-info (up through at least version 1.9.20) uses only the -@c first dircategory. Put this one first, as it is more useful in practice. -@dircategory Individual utilities +@c first dircategory. But install-info 1.10.28 rejects any attempt to +@c put the more-useful individual utility first. So put the less-useful +@c general category first. +@dircategory Utilities @direntry -* gzip: (gzip)Invoking gzip. Compress files. +* Gzip: (gzip). The gzip command for compressing files. @end direntry -@dircategory Utilities +@dircategory Individual utilities @direntry -* Gzip: (gzip). The gzip command for compressing files. +* gzip: (gzip)Invoking gzip. Compress files. @end direntry @titlepage @@ -53,7 +55,7 @@ Free Documentation License''. @contents @ifnottex -@node Top, , , (dir) +@node Top @top Compressing Files @insertcopying @@ -61,180 +63,194 @@ Free Documentation License''. @menu * Overview:: Preliminary information. -* Sample:: Sample output from @code{gzip}. -* Invoking gzip:: How to run @code{gzip}. +* Sample:: Sample output from @command{gzip}. +* Invoking gzip:: How to run @command{gzip}. * Advanced usage:: Concatenated files. -* Environment:: The @code{GZIP} environment variable -* Tapes:: Using @code{gzip} on tapes. +* Environment:: The @env{GZIP} environment variable +* Tapes:: Using @command{gzip} on tapes. * Problems:: Reporting bugs. * Copying This Manual:: How to make copies of this manual. * Concept Index:: Index of concepts. @end menu -@node Overview, Sample, , Top +@node Overview @chapter Overview @cindex overview -@code{gzip} reduces the size of the named files using Lempel-Ziv coding +@command{gzip} reduces the size of the named files using Lempel-Ziv coding (LZ77). Whenever possible, each file is replaced by one with the extension @samp{.gz}, while keeping the same ownership modes, access and -modification times. (The default extension is @samp{-gz} for VMS, -@samp{z} for MSDOS, OS/2 FAT and Atari.) If no files are specified or +modification times. (The default extension is @option{-gz} for @abbr{VMS}, +@samp{z} for @abbr{MSDOS}, @abbr{OS/2} @abbr{FAT} and Atari.) +If no files are specified or if a file name is "-", the standard input is compressed to the standard -output. @code{gzip} will only attempt to compress regular files. In +output. @command{gzip} will only attempt to compress regular files. In particular, it will ignore symbolic links. -If the new file name is too long for its file system, @code{gzip} -truncates it. @code{gzip} attempts to truncate only the parts of the +If the new file name is too long for its file system, @command{gzip} +truncates it. @command{gzip} attempts to truncate only the parts of the file name longer than 3 characters. (A part is delimited by dots.) If the name consists of small parts only, the longest parts are truncated. For example, if file names are limited to 14 characters, gzip.msdos.exe is compressed to gzi.msd.exe.gz. Names are not truncated on systems which do not have a limit on file name length. -By default, @code{gzip} keeps the original file name and timestamp in -the compressed file. These are used when decompressing the file with the -@samp{-N} option. This is useful when the compressed file name was +By default, @command{gzip} keeps the original file name and time stamp in +the compressed file. These are used when decompressing the file with the +@option{-N} option. This is useful when the compressed file name was truncated or when the time stamp was not preserved after a file -transfer. However, due to limitations in the current @code{gzip} file +transfer. However, due to limitations in the current @command{gzip} file format, fractional seconds are discarded. Also, time stamps must fall within the range 1970-01-01 00:00:00 through 2106-02-07 06:28:15 -@acronym{UTC}, and hosts whose operating systems use 32-bit time +@abbr{UTC}, and hosts whose operating systems use 32-bit time stamps are further restricted to time stamps no later than 2038-01-19 -03:14:07 @acronym{UTC}. The upper bounds assume the typical case +03:14:07 @abbr{UTC}. The upper bounds assume the typical case where leap seconds are ignored. Compressed files can be restored to their original form using @samp{gzip -d} -or @code{gunzip} or @code{zcat}. If the original name saved in the +or @command{gunzip} or @command{zcat}. If the original name saved in the compressed file is not suitable for its file system, a new name is constructed from the original one to make it legal. -@code{gunzip} takes a list of files on its command line and replaces +@command{gunzip} takes a list of files on its command line and replaces each file whose name ends with @samp{.gz}, @samp{.z}, @samp{.Z}, -@samp{-gz}, @samp{-z} or @samp{_z} and which begins with the correct +@option{-gz}, @option{-z} or @samp{_z} and which begins with the correct magic number with an uncompressed file without the original extension. -@code{gunzip} also recognizes the special extensions @samp{.tgz} and +@command{gunzip} also recognizes the special extensions @samp{.tgz} and @samp{.taz} as shorthands for @samp{.tar.gz} and @samp{.tar.Z} -respectively. When compressing, @code{gzip} uses the @samp{.tgz} +respectively. When compressing, @command{gzip} uses the @samp{.tgz} extension if necessary instead of truncating a file with a @samp{.tar} extension. -@code{gunzip} can currently decompress files created by @code{gzip}, -@code{zip}, @code{compress} or @code{pack}. The detection of the input -format is automatic. When using the first two formats, @code{gunzip} -checks a 32 bit CRC (cyclic redundancy check). For @code{pack}, -@code{gunzip} checks the uncompressed length. The @code{compress} format -was not designed to allow consistency checks. However @code{gunzip} is -sometimes able to detect a bad @samp{.Z} file. If you get an error when +@command{gunzip} can currently decompress files created by @command{gzip}, +@command{zip}, @command{compress} or @command{pack}. The detection of the input +format is automatic. When using the first two formats, @command{gunzip} +checks a 32 bit @abbr{CRC} (cyclic redundancy check). For @command{pack}, +@command{gunzip} checks the uncompressed length. The @command{compress} format +was not designed to allow consistency checks. However @command{gunzip} is +sometimes able to detect a bad @samp{.Z} file. If you get an error when uncompressing a @samp{.Z} file, do not assume that the @samp{.Z} file is -correct simply because the standard @code{uncompress} does not complain. -This generally means that the standard @code{uncompress} does not check -its input, and happily generates garbage output. The SCO @samp{compress --H} format (@code{lzh} compression method) does not include a CRC but +correct simply because the standard @command{uncompress} does not complain. +This generally means that the standard @command{uncompress} does not check +its input, and happily generates garbage output. The @abbr{SCO} @samp{compress +-H} format (@abbr{LZH} compression method) does not include a @abbr{CRC} but also allows some consistency checks. -Files created by @code{zip} can be uncompressed by @code{gzip} only if -they have a single member compressed with the 'deflation' method. This -feature is only intended to help conversion of @code{tar.zip} files to -the @code{tar.gz} format. To extract a @code{zip} file with a single +Files created by @command{zip} can be uncompressed by @command{gzip} only if +they have a single member compressed with the 'deflation' method. This +feature is only intended to help conversion of @file{tar.zip} files to +the @file{tar.gz} format. To extract a @command{zip} file with a single member, use a command like @samp{gunzip . @end example This is the output of the command @samp{gzip -v texinfo.tex}: @example -texinfo.tex: 69.7% -- replaced with texinfo.tex.gz +texinfo.tex: 69.3% -- replaced with texinfo.tex.gz @end example -The following command will find all @code{gzip} files in the current -directory and subdirectories, and extract them in place without -destroying the original: +The following command will find all regular @samp{.gz} files in the +current directory and subdirectories (skipping file names that contain +newlines), and extract them in place without destroying the original, +stopping on the first failure: @example -find . -name '*.gz' -print | sed 's/^\(.*\)[.]gz$/gunzip < "&" > "\1"/' | sh +find . -name '* +*' -prune -o -name '*.gz' -type f -print | + sed " + s/'/'\\''/g + s/^\\(.*\\)\\.gz$/gunzip <'\\1.gz' >'\\1'/ + " | + sh -e @end example -@node Invoking gzip, Advanced usage, Sample, Top -@chapter Invoking @code{gzip} +@node Invoking gzip +@chapter Invoking @command{gzip} @cindex invoking @cindex options -The format for running the @code{gzip} program is: +The format for running the @command{gzip} program is: @example gzip @var{option} @dots{} @end example -@code{gzip} supports the following options: +@command{gzip} supports the following options: -@table @samp +@table @option @item --stdout @itemx --to-stdout @itemx -c Write output on standard output; keep original files unchanged. If there are several input files, the output consists of a sequence of -independently compressed members. To obtain better compression, +independently compressed members. To obtain better compression, concatenate all input files before compressing them. @item --decompress @@ -246,11 +262,11 @@ Decompress. @itemx -f Force compression or decompression even if the file has multiple links or the corresponding file already exists, or if the compressed data -is read from or written to a terminal. If the input data is not in -a format recognized by @code{gzip}, and if the option @samp{--stdout} is also +is read from or written to a terminal. If the input data is not in +a format recognized by @command{gzip}, and if the option @option{--stdout} is also given, copy the input data without change to the standard output: let -@code{zcat} behave as @code{cat}. If @samp{-f} is not given, and -when not running in the background, @code{gzip} prompts to verify +@command{zcat} behave as @command{cat}. If @option{-f} is not given, and +when not running in the background, @command{gzip} prompts to verify whether an existing file should be overwritten. @item --help @@ -268,15 +284,15 @@ ratio: compression ratio (0.0% if unknown) uncompressed_name: name of the uncompressed file @end example -The uncompressed size is given as @samp{-1} for files not in @code{gzip} -format, such as compressed @samp{.Z} files. To get the uncompressed size for +The uncompressed size is given as @minus{}1 for files not in @command{gzip} +format, such as compressed @samp{.Z} files. To get the uncompressed size for such a file, you can use: @example zcat file.Z | wc -c @end example -In combination with the @samp{--verbose} option, the following fields are also +In combination with the @option{--verbose} option, the following fields are also displayed: @example @@ -285,15 +301,15 @@ crc: the 32-bit CRC of the uncompressed data date & time: time stamp for the uncompressed file @end example -The crc is given as ffffffff for a file not in gzip format. +The @abbr{CRC} is given as ffffffff for a file not in gzip format. -With @samp{--verbose}, the size totals and compression ratio for all files -is also displayed, unless some sizes are unknown. With @samp{--quiet}, +With @option{--verbose}, the size totals and compression ratio for all files +is also displayed, unless some sizes are unknown. With @option{--quiet}, the title and totals lines are not displayed. -The @code{gzip} format represents the input size modulo +The @command{gzip} format represents the input size modulo @math{2^32}, so the uncompressed size and compression ratio are listed -incorrectly for uncompressed files 4 GB and larger. To work around +incorrectly for uncompressed files 4 GiB and larger. To work around this problem, you can use the following command to discover a large uncompressed file's true size: @@ -303,23 +319,23 @@ zcat file.gz | wc -c @item --license @itemx -L -Display the @code{gzip} license then quit. +Display the @command{gzip} license then quit. @item --no-name @itemx -n When compressing, do not save the original file name and time stamp by -default. (The original name is always saved if the name had to be -truncated.) When decompressing, do not restore the original file name -if present (remove only the @code{gzip} +default. (The original name is always saved if the name had to be +truncated.) When decompressing, do not restore the original file name +if present (remove only the @command{gzip} suffix from the compressed file name) and do not restore the original -time stamp if present (copy it from the compressed file). This option +time stamp if present (copy it from the compressed file). This option is the default when decompressing. @item --name @itemx -N When compressing, always save the original file name and time stamp; this -is the default. When decompressing, restore the original file name and -time stamp if present. This option is useful on systems which have +is the default. When decompressing, restore the original file name and +time stamp if present. This option is useful on systems which have a limit on file name length or when the time stamp has been lost after a file transfer. @@ -329,14 +345,14 @@ Suppress all warning messages. @item --recursive @itemx -r -Travel the directory structure recursively. If any of the file names -specified on the command line are directories, @code{gzip} will descend +Travel the directory structure recursively. If any of the file names +specified on the command line are directories, @command{gzip} will descend into the directory and compress all the files it finds there (or -decompress them in the case of @code{gunzip}). +decompress them in the case of @command{gunzip}). @item --suffix @var{suf} @itemx -S @var{suf} -Use suffix @samp{@var{suf}} instead of @samp{.gz}. Any suffix can be +Use suffix @var{suf} instead of @samp{.gz}. Any suffix can be given, but suffixes other than @samp{.z} and @samp{.gz} should be avoided to avoid confusion when files are transferred to other systems. A null suffix forces gunzip to try decompression on all given files @@ -346,55 +362,57 @@ regardless of suffix, as in: gunzip -S "" * (*.* for MSDOS) @end example -Previous versions of gzip used the @samp{.z} suffix. This was changed to -avoid a conflict with @code{pack}. +Previous versions of gzip used the @samp{.z} suffix. This was changed to +avoid a conflict with @command{pack}. @item --test @itemx -t -Test. Check the compressed file integrity. +Test. Check the compressed file integrity. @item --verbose @itemx -v -Verbose. Display the name and percentage reduction for each file compressed. +Verbose. Display the name and percentage reduction for each file compressed. @item --version @itemx -V -Version. Display the version number and compilation options, then quit. +Version. Display the version number and compilation options, then quit. @item --fast @itemx --best @itemx -@var{n} Regulate the speed of compression using the specified digit @var{n}, -where @samp{-1} or @samp{--fast} indicates the fastest compression -method (less compression) and @samp{--best} or @samp{-9} indicates the +where @option{-1} or @option{--fast} indicates the fastest compression +method (less compression) and @option{--best} or @option{-9} indicates the slowest compression method (optimal compression). The default -compression level is @samp{-6} (that is, biased towards high compression at +compression level is @option{-6} (that is, biased towards high compression at expense of speed). @end table -@node Advanced usage, Environment, Invoking gzip, Top +@node Advanced usage @chapter Advanced usage @cindex concatenated files -Multiple compressed files can be concatenated. In this case, -@code{gunzip} will extract all members at once. If one member is +Multiple compressed files can be concatenated. In this case, +@command{gunzip} will extract all members at once. If one member is damaged, other members might still be recovered after removal of the -damaged member. Better compression can be usually obtained if all +damaged member. Better compression can be usually obtained if all members are decompressed and then recompressed in a single step. -This is an example of concatenating @code{gzip} files: +This is an example of concatenating @command{gzip} files: @example gzip -c file1 > foo.gz gzip -c file2 >> foo.gz @end example +@noindent Then @example gunzip -c foo @end example +@noindent is equivalent to @example @@ -402,13 +420,14 @@ cat file1 file2 @end example In case of damage to one member of a @samp{.gz} file, other members can -still be recovered (if the damaged member is removed). However, +still be recovered (if the damaged member is removed). However, you can get better compression by compressing all members at once: @example cat file1 file2 | gzip > foo.gz @end example +@noindent compresses better than @example @@ -422,8 +441,9 @@ zcat old.gz | gzip > new.gz @end example If a compressed file consists of several members, the uncompressed -size and CRC reported by the @samp{--list} option applies to the last member -only. If you need the uncompressed size for all members, you can use: +size and @abbr{CRC} reported by the @option{--list} option applies to +the last member +only. If you need the uncompressed size for all members, you can use: @example zcat file.gz | wc -c @@ -431,16 +451,17 @@ zcat file.gz | wc -c If you wish to create a single archive file with multiple members so that members can later be extracted independently, use an archiver such -as @code{tar} or @code{zip}. GNU @code{tar} supports the @samp{-z} -option to invoke @code{gzip} transparently. @code{gzip} is designed as a -complement to @code{tar}, not as a replacement. +as @command{tar} or @command{zip}. @acronym{GNU} @command{tar} +supports the @option{-z} +option to invoke @command{gzip} transparently. @command{gzip} is designed as a +complement to @command{tar}, not as a replacement. -@node Environment, Tapes, Advanced usage, Top +@node Environment @chapter Environment @cindex Environment -The environment variable @code{GZIP} can hold a set of default options for -@code{gzip}. These options are interpreted first and can be overwritten by +The environment variable @env{GZIP} can hold a set of default options for +@command{gzip}. These options are interpreted first and can be overwritten by explicit command line parameters. For example: @example @@ -449,46 +470,48 @@ for csh: setenv GZIP "-8v --name" for MSDOS: set GZIP=-8v --name @end example -On Vax/VMS, the name of the environment variable is @code{GZIP_OPT}, to +On @abbr{VMS}, the name of the environment variable is @env{GZIP_OPT}, to avoid a conflict with the symbol set for invocation of the program. -@node Tapes, Problems, Environment, Top -@chapter Using @code{gzip} on tapes +@node Tapes +@chapter Using @command{gzip} on tapes @cindex tapes When writing compressed data to a tape, it is generally necessary to pad -the output with zeroes up to a block boundary. When the data is read and -the whole block is passed to @code{gunzip} for decompression, -@code{gunzip} detects that there is extra trailing garbage after the +the output with zeroes up to a block boundary. When the data is read and +the whole block is passed to @command{gunzip} for decompression, +@command{gunzip} detects that there is extra trailing garbage after the compressed data and emits a warning by default if the garbage contains -nonzero bytes. You have to use the -@samp{--quiet} option to suppress the warning. This option can be set in the -@code{GZIP} environment variable, as in: +nonzero bytes. You have to use the +@option{--quiet} option to suppress the warning. This option can be set in the +@env{GZIP} environment variable, as in: @example for sh: GZIP="-q" tar -xfz --block-compress /dev/rst0 for csh: (setenv GZIP "-q"; tar -xfz --block-compress /dev/rst0) @end example -In the above example, @code{gzip} is invoked implicitly by the @samp{-z} -option of GNU @code{tar}. Make sure that the same block size (@samp{-b} -option of @code{tar}) is used for reading and writing compressed data on -tapes. (This example assumes you are using the GNU version of -@code{tar}.) +In the above example, @command{gzip} is invoked implicitly by the @option{-z} +option of @acronym{GNU} @command{tar}. Make sure that the same block +size (@option{-b} +option of @command{tar}) is used for reading and writing compressed data on +tapes. (This example assumes you are using the @acronym{GNU} version of +@command{tar}.) -@node Problems, Copying This Manual, Tapes, Top +@node Problems @chapter Reporting Bugs @cindex bugs -If you find a bug in @code{gzip}, please send electronic mail to +If you find a bug in @command{gzip}, please send electronic mail to @email{bug-gzip@@gnu.org}. Include the version number, which you can find by running @w{@samp{gzip -V}}. Also include in your message the hardware and operating system, the compiler used to compile -@code{gzip}, -a description of the bug behavior, and the input to @code{gzip} that triggered +@command{gzip}, +a description of the bug behavior, and the input to @command{gzip} +that triggered the bug.@refill -@node Copying This Manual, Concept Index, Problems, Top +@node Copying This Manual @appendix Copying This Manual @menu @@ -497,7 +520,7 @@ the bug.@refill @include fdl.texi -@node Concept Index, , Copying This Manual, Top +@node Concept Index @appendix Concept Index @printindex cp