![]() These options are interpreted first and can be overwritten by explicit command line parameters. The environment variable GZIP can hold a set of default options for gzip. gzip is designed as a complement to tar, not as a replacement. GNU tar supports the -z option to invoke gzip transparently. If you want 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. If you need the uncompressed size for all members, you can use: gzip -cd file.gz | wc -c ![]() 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 want to recompress concatenated files to get better compression, do: gzip -cd old.gz | gzip > new.gz However, you can get better compression by compressing all members at once: cat file1 file2 | gzip > foo.gzĬompresses better than: gzip -c file1 file2 > foo.gz gz file, other members can still be recovered (if the damaged member is removed). ![]() To extract a zip file with a single member, use a command like: gunzip foo.gz gzip -c file2 > foo.gz This feature is only intended to help conversion of tar.zip files to the tar.gz format. The SCO compress -H format (lzh compression method) does not include a CRC but also allows some consistency checks.įiles created by zip can be uncompressed by gzip only if they have a single member compressed with the 'deflation' method. This generally indicates the standard uncompress does not check its input, and happily generates garbage output. Z file is correct because the standard uncompress does not complain. If you get an error when uncompressing a. However gunzip is sometimes able to detect a bad. The standard compress format was not designed to allow consistency checks. For pack, gunzip checks the uncompressed length. When using the first two formats, gunzip checks a 32-bit CRC. The detection of the input format is automatic. Gunzip can currently decompress files created by gzip, zip, compress, compress -H or pack. tgz extension if necessary instead of truncating a file with a. gunzip also recognizes the special extensions. z, -z, or _z (ignoring case) and which begins with the correct magic number with an uncompressed file without the original extension. Gunzip takes a list of files on its command line and replaces each file whose name ends with. 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. This setting is useful when the compressed file name was truncated or when the timestamp was not preserved after a file transfer.Ĭompressed files can be restored to their original form using gzip -d or gunzip or zcat. These are used when decompressing the file with the -N option. Names are not truncated on systems which do not have a limit on file name length.īy default, gzip keeps the original file name and timestamp in the compressed file. For example, if file names are limited to 14 characters, is compressed to. (A part is delimited by dots.) If the name consists of small parts only, the longest parts are truncated. gzip attempts to truncate only the parts of the file name longer than three characters. If the compressed file name is too long for its file system, gzip truncates it. In particular, it ignores symbolic links. gzip only attempts to compress regular files. (The default extension is -gz for VMS, z for MS-DOS, 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. gz, while keeping the same ownership modes, access and modification times. Whenever possible, each file is replaced by one with the extension. Gzip reduces the size of the named files using Lempel- Ziv coding (LZ77).
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