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diff --git a/Build/source/utils/gzip/gzip.1 b/Build/source/utils/gzip/gzip.1 new file mode 100644 index 00000000000..6fa79862bfc --- /dev/null +++ b/Build/source/utils/gzip/gzip.1 @@ -0,0 +1,478 @@ +.PU +.TH GZIP 1 local +.SH NAME +gzip, gunzip, zcat \- compress or expand files +.SH SYNOPSIS +.ll +8 +.B gzip +.RB [ " \-acdfhlLnNrtvV19 " ] +.RB [ \-S\ suffix ] +[ +.I "name \&..." +] +.ll -8 +.br +.B gunzip +.RB [ " \-acfhlLnNrtvV " ] +.RB [ \-S\ suffix ] +[ +.I "name \&..." +] +.br +.B zcat +.RB [ " \-fhLV " ] +[ +.I "name \&..." +] +.SH DESCRIPTION +.I Gzip +reduces the size of the named files using Lempel-Ziv coding (LZ77). +Whenever possible, +each file is replaced by one with the extension +.B "\&.gz," +while keeping the same ownership modes, access and modification times. +(The default extension is +.B "\-gz" +for VMS, +.B "z" +for MSDOS, OS/2 FAT, Windows NT FAT and Atari.) +If no files are specified, or if a file name is "-", the standard input is +compressed to the standard output. +.I Gzip +will only attempt to compress regular files. +In particular, it will ignore symbolic links. +.PP +If the compressed file name is too long for its file system, +.I gzip +truncates it. +.I 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. +.PP +By default, +.I gzip +keeps the original file name and timestamp in the compressed file. These +are used when decompressing the file with the +.B \-N +option. This is useful when the compressed file name was truncated or +when the time stamp was not preserved after a file transfer. +.PP +Compressed files can be restored to their original form using +.I gzip -d +or +.I gunzip +or +.I 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. +.PP +.I gunzip +takes a list of files on its command line and replaces each +file whose name ends with .gz, -gz, .z, -z, _z or .Z +and which begins with the correct magic number with an uncompressed +file without the original extension. +.I gunzip +also recognizes the special extensions +.B "\&.tgz" +and +.B "\&.taz" +as shorthands for +.B "\&.tar.gz" +and +.B "\&.tar.Z" +respectively. +When compressing, +.I gzip +uses the +.B "\&.tgz" +extension if necessary instead of truncating a file with a +.B "\&.tar" +extension. +.PP +.I gunzip +can currently decompress files created by +.I gzip, zip, compress, compress -H +or +.I pack. +The detection of the input format is automatic. When using +the first two formats, +.I gunzip +checks a 32 bit CRC. For +.I pack, gunzip +checks the uncompressed length. The standard +.I compress +format was not designed to allow consistency checks. However +.I gunzip +is sometimes able to detect a bad .Z file. If you get an error +when uncompressing a .Z file, do not assume that the .Z file is +correct simply because the standard +.I uncompress +does not complain. This generally means that the standard +.I uncompress +does not check its input, and happily generates garbage output. +The SCO compress -H format (lzh compression method) does not include a CRC +but also allows some consistency checks. +.PP +Files created by +.I zip +can be uncompressed by gzip only if they have a single member compressed +with the 'deflation' method. This feature is only intended to help +conversion of tar.zip files to the tar.gz format. To extract zip files +with several members, use +.I unzip +instead of +.I gunzip. +.PP +.I zcat +is identical to +.I gunzip +.B \-c. +(On some systems, +.I zcat +may be installed as +.I gzcat +to preserve the original link to +.I compress.) +.I zcat +uncompresses either a list of files on the command line or its +standard input and writes the uncompressed data on standard output. +.I zcat +will uncompress files that have the correct magic number whether +they have a +.B "\&.gz" +suffix or not. +.PP +.I Gzip +uses the Lempel-Ziv algorithm used in +.I zip +and PKZIP. +The amount of compression obtained depends on the size of the +input and the distribution of common substrings. +Typically, text such as source code or English +is reduced by 60\-70%. +Compression is generally much better than that achieved by +LZW (as used in +.IR compress ), +Huffman coding (as used in +.IR pack ), +or adaptive Huffman coding +.RI ( compact ). +.PP +Compression is always performed, even if the compressed file is +slightly larger than the original. The worst case expansion is +a few bytes for the gzip file header, plus 5 bytes every 32K block, +or an expansion ratio of 0.015% for large files. Note that the actual +number of used disk blocks almost never increases. +.I gzip +preserves the mode, ownership and timestamps of files when compressing +or decompressing. + +.SH OPTIONS +.TP +.B \-a --ascii +Ascii text mode: convert end-of-lines using local conventions. This option +is supported only on some non-Unix systems. For MSDOS, CR LF is converted +to LF when compressing, and LF is converted to CR LF when decompressing. +.TP +.B \-c --stdout --to-stdout +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, +concatenate all input files before compressing them. +.TP +.B \-d --decompress --uncompress +Decompress. +.TP +.B \-f --force +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 +.I gzip, +and if the option --stdout is also given, copy the input data without change +to the standard ouput: let +.I zcat +behave as +.I cat. +If +.B \-f +is not given, +and when not running in the background, +.I gzip +prompts to verify whether an existing file should be overwritten. +.TP +.B \-h --help +Display a help screen and quit. +.TP +.B \-l --list +For each compressed file, list the following fields: + + compressed size: size of the compressed file + uncompressed size: size of the uncompressed file + ratio: compression ratio (0.0% if unknown) + uncompressed_name: name of the uncompressed file + +The uncompressed size is given as -1 for files not in gzip format, +such as compressed .Z files. To get the uncompressed size for such a file, +you can use: + + zcat file.Z | wc -c + +In combination with the --verbose option, the following fields are also +displayed: + + method: compression method + crc: the 32-bit CRC of the uncompressed data + date & time: time stamp for the uncompressed file + +The compression methods currently supported are deflate, compress, lzh +(SCO compress -H) and pack. The crc is given as ffffffff for a file +not in gzip format. + +With --name, the uncompressed name, date and time are +those stored within the compress file if present. + +With --verbose, the size totals and compression ratio for all files +is also displayed, unless some sizes are unknown. With --quiet, +the title and totals lines are not displayed. +.TP +.B \-L --license +Display the +.I gzip +license and quit. +.TP +.B \-n --no-name +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 +.I 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 +is the default when decompressing. +.TP +.B \-N --name +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 +a limit on file name length or when the time stamp has been lost after +a file transfer. +.TP +.B \-q --quiet +Suppress all warnings. +.TP +.B \-r --recursive +Travel the directory structure recursively. If any of the file names +specified on the command line are directories, +.I gzip +will descend into the directory and compress all the files it finds there +(or decompress them in the case of +.I gunzip +). +.TP +.B \-S .suf --suffix .suf +Use suffix .suf instead of .gz. Any suffix can be given, but suffixes +other than .z and .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 regardless of suffix, as in: + + gunzip -S "" * (*.* for MSDOS) + +Previous versions of gzip used +the .z suffix. This was changed to avoid a conflict with +.IR pack "(1)". +.TP +.B \-t --test +Test. Check the compressed file integrity. +.TP +.B \-v --verbose +Verbose. Display the name and percentage reduction for each file compressed +or decompressed. +.TP +.B \-V --version +Version. Display the version number and compilation options then quit. +.TP +.B \-# --fast --best +Regulate the speed of compression using the specified digit +.IR # , +where +.B \-1 +or +.B \-\-fast +indicates the fastest compression method (less compression) +and +.B \-9 +or +.B \-\-best +indicates the slowest compression method (best compression). +The default compression level is +.BR \-6 +(that is, biased towards high compression at expense of speed). +.SH "ADVANCED USAGE" +Multiple compressed files can be concatenated. In this case, +.I gunzip +will extract all members at once. For example: + + gzip -c file1 > foo.gz + gzip -c file2 >> foo.gz + +Then + gunzip -c foo + +is equivalent to + + cat file1 file2 + +In case of damage to one member of a .gz file, other members can +still be recovered (if the damaged member is removed). However, +you can get better compression by compressing all members at once: + + cat file1 file2 | gzip > foo.gz + +compresses better than + + gzip -c file1 file2 > foo.gz + +If you want to recompress concatenated files to get better compression, do: + + gzip -cd old.gz | gzip > new.gz + +If a compressed file consists of several members, the uncompressed +size and CRC reported by the --list option applies to the last member +only. If you need the uncompressed size for all members, you can use: + + gzip -cd 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 tar or zip. GNU tar supports the -z option to invoke gzip +transparently. gzip is designed as a complement to tar, not as a +replacement. +.SH "ENVIRONMENT" +The environment variable +.B GZIP +can hold a set of default options for +.I gzip. +These options are interpreted first and can be overwritten by +explicit command line parameters. For example: + for sh: GZIP="-8v --name"; export GZIP + for csh: setenv GZIP "-8v --name" + for MSDOS: set GZIP=-8v --name + +On Vax/VMS, the name of the environment variable is GZIP_OPT, to +avoid a conflict with the symbol set for invocation of the program. +.SH "SEE ALSO" +znew(1), zcmp(1), zmore(1), zforce(1), gzexe(1), zip(1), unzip(1), compress(1), +pack(1), compact(1) +.SH "DIAGNOSTICS" +Exit status is normally 0; +if an error occurs, exit status is 1. If a warning occurs, exit status is 2. +.PP +Usage: gzip [-cdfhlLnNrtvV19] [-S suffix] [file ...] +.in +8 +Invalid options were specified on the command line. +.in -8 +.IR file : +not in gzip format +.in +8 +The file specified to +.I gunzip +has not been compressed. +.in -8 +.IR file: +Corrupt input. Use zcat to recover some data. +.in +8 +The compressed file has been damaged. The data up to the point of failure +can be recovered using +.in +8 +zcat file > recover +.in -16 +.IR file : +compressed with +.I xx +bits, can only handle +.I yy +bits +.in +8 +.I File +was compressed (using LZW) by a program that could deal with +more +.I bits +than the decompress code on this machine. +Recompress the file with gzip, which compresses better and uses +less memory. +.in -8 +.IR file : +already has .gz suffix -- no change +.in +8 +The file is assumed to be already compressed. +Rename the file and try again. +.in -8 +.I file +already exists; do you wish to overwrite (y or n)? +.in +8 +Respond "y" if you want the output file to be replaced; "n" if not. +.in -8 +gunzip: corrupt input +.in +8 +A SIGSEGV violation was detected which usually means that the input file has +been corrupted. +.in -8 +.I "xx.x%" +.in +8 +Percentage of the input saved by compression. +(Relevant only for +.BR \-v +and +.BR \-l \.) +.in -8 +-- not a regular file or directory: ignored +.in +8 +When the input file is not a regular file or directory, +(e.g. a symbolic link, socket, FIFO, device file), it is +left unaltered. +.in -8 +-- has +.I xx +other links: unchanged +.in +8 +The input file has links; it is left unchanged. See +.IR ln "(1)" +for more information. Use the +.B \-f +flag to force compression of multiply-linked files. +.in -8 +.SH CAVEATS +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 +.I gunzip +for decompression, +.I gunzip +detects that there is extra trailing garbage after the compressed data +and emits a warning by default. You have to use the --quiet option to +suppress the warning. This option can be set in the +.B GZIP +environment variable as in: + for sh: GZIP="-q" tar -xfz --block-compress /dev/rst0 + for csh: (setenv GZIP -q; tar -xfz --block-compr /dev/rst0 + +In the above example, gzip is invoked implicitly by the -z option of +GNU tar. Make sure that the same block size (-b option of tar) is used +for reading and writing compressed data on tapes. (This example +assumes you are using the GNU version of tar.) +.SH BUGS +The --list option reports incorrect sizes if they exceed 2 gigabytes. +The --list option reports sizes as -1 and crc as ffffffff if the +compressed file is on a non seekable media. + +In some rare cases, the --best option gives worse compression than +the default compression level (-6). On some highly redundant files, +.I compress +compresses better than +.I gzip. |