The gzip command shall attempt to reduce the size of the named files. Whenever possible, each file is replaced by one with the extension .gz, while keeping the same ownership, modes, access and modification times. If no files are specified, or if a file name is -, the standard input is compressed to the standard output. gzip shall only attempt to compress regular files. In particular, it will ignore symbolic links.
When compressing, gzip uses the deflate algorithm specified in RFC 1951: DEFLATE Compressed Data Format Specification and stores the result in a file using the gzip file format specified in RFC 1952: GZIP File Format Specification.
writes output on standard output, leaving the 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.
the name operands are compressed files, and gzip shall decompress them.
forces 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 gzip, and if the option --stdout is also given, copy the input data without change to the standard ouput: let gzip behave as cat. If -f is not given, and when not running in the background, gzip prompts to verify whether an existing file should be overwritten.
lists the compressed size, uncompressed size, ratio and uncompressed
name for each compressed file. For files that are not in gzip
format, the uncompressed size shall be given as
If the --verbose or -v option
is also specified, the
crc and timestamp for the uncompressed file shall also be displayed.
For decompression, gzip shall support at least the following compression methods:
compress (ISO POSIX (2003))
fffffffffor a file not in gzip format.
If the --name or -N option is also specified, the uncompressed name, date and time are those stored within the compressed file, if present.
If the --quiet or -q option is also specified, the title and totals lines are not displayed.
displays the gzip license and quit.
does not save the original file name and time stamp by default when compressing. (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 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.
always saves the original file name and time stamp when compressing; 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.
suppresses all warnings.
travels the directory structure recursively. If any of the file names specified on the command line are directories, gzip will descend into the directory and compress all the files it finds there (or decompress them in the case of gunzip).
uses suffix .suf instead of .gz.
checks the compressed file integrity.
displays the name and percentage reduction for each file compressed or decompressed.
regulates the speed of compression using the specified digit #, where -1 or --fast indicates the fastest compression method (less compression) and -9 or --best indicates the slowest compression method (best compression). The default compression level is -6 (that is, biased towards high compression at expense of speed).
The behaviors specified in this section are expected to disappear from a future version of the LSB; applications should only use the non-LSB-deprecated behaviors.
displays the version number and compilation options, then quits.