--- name: "gunzip" section: "1" platform: "linux" package: "gzip" version: "1.15-1" release: "Arch Linux 2026-11-01" platforms: ["linux", "freebsd"] url: "https://new.carta.tech/gzip" --- # gunzip(1) compress or expand files Part of [gzip(1)](/gzip/1.md). ## NAME gzip, gunzip, zcat - compress or expand files ## SYNOPSIS **gzip** \[ **-acdfhklLnNrtvV19** \] \[**-S suffix**\] \[ *name ...* \]\ **gunzip** \[ **-acfhklLnNrtvV** \] \[**-S suffix**\] \[ *name ...* \]\ **zcat** \[ **-fhLV** \] \[ *name ...* \] ## DESCRIPTION The **gzip** command reduces the size of the named files using Lempel-Ziv coding (LZ77). Whenever possible, each file is replaced by one with the extension **.gz**, while keeping the same ownership modes, access and modification times. (The default extension is **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. The **gzip** command will only attempt to compress regular files. In particular, it will ignore symbolic links. If the compressed file name is too long for its file system, **gzip** truncates it. The **gzip** command 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, **gzip** keeps the original file name and timestamp in the compressed file. These are used when decompressing the file with the **-N** option. This is useful when the compressed file name was truncated or when the timestamp was not preserved after a file transfer. Compressed files can be restored to their original form using **gzip -d** or **gunzip** or **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 valid. **gunzip** takes a list of files on its command line and replaces each file whose name ends with .gz, -gz, .z, -z, or \_z (ignoring case) and which begins with the correct magic number with an uncompressed file without the original extension. **gunzip** also recognizes the special extensions **.tgz** and **.taz** as shorthands for **.tar.gz** and **.tar.Z** respectively. When compressing, **gzip** uses the **.tgz** extension if necessary instead of truncating a file with a **.tar** extension. **gunzip** can currently decompress files created by **gzip**, **zip**, **compress**, **compress -H** or **pack**. The detection of the input format is automatic. When using the first two formats, **gunzip** checks a 32 bit CRC. For **pack** and **gunzip** checks the uncompressed length. The standard **compress** format was not designed to allow consistency checks. However **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 **uncompress** does not complain. This generally means that the standard **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. Files created by **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 a **zip** file with a single member, use a command like '**gunzip \ 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. ## ENVIRONMENT The environment variable **GZIP** can hold a set of default options for **gzip**. These options are interpreted first and can be overridden by explicit command line parameters. As this can cause problems when using scripts, this feature is supported only for --rsyncable, --synchronous, and options like -9 that set the compression level; any other options or operands in **GZIP** are silently ignored. You can use an alias or script instead. For example, instead of setting GZIP="-9" in the environment, if **gzip** is in the directory **/usr/bin** you can prepend **$HOME/bin** to your **PATH** and create an executable script **$HOME/bin/gzip** containing the following: \#! /bin/sh\ export PATH=/usr/bin\ exec gzip -9 "$@" ## SEE ALSO [**znew**(1)](/znew/1.md), [**zcmp**(1)](/zcmp/1.md), [**zmore**(1)](/zmore/1.md), [**zforce**(1)](/zforce/1.md), [**gzexe**(1)](/gzexe/1.md), [**pigz**(1)](/pigz/1.md), [**zip**(1)](/zip/1.md), [**unzip**(1)](/unzip/1.md), [**compress**(1)](/compress/1.md) The **gzip** file format is specified in P. Deutsch, GZIP file format specification version 4.3, **\**, Internet RFC 1952 (May 1996). The **zip** deflation format is specified in P. Deutsch, DEFLATE Compressed Data Format Specification version 1.3, **\**, Internet RFC 1951 (May 1996). The **zlib** compression library can be used to programmatically read and write gzip-format data. See **\**. ## DIAGNOSTICS Exit status is normally 0; if an error occurs, exit status is 1. If a warning occurs, exit status is 2. - Usage: gzip \[-cdfhklLnNrtvV19\] \[-S suffix\] \[file ...\] Invalid options were specified on the command line. - *file*: not in gzip format The file specified to **gunzip** has not been compressed. - *file*: Corrupt input. Use zcat to recover some data. The compressed file has been damaged. The data up to the point of failure can be recovered using zcat *file* \> recover - *file*: compressed with *xx* bits, can only handle *yy* bits **File** was compressed (using LZW) by a program that could deal with more bits than the decompress code on this machine. Recompress the file with gzip, which compresses better and uses less memory. - *file*: already has .gz suffix -- unchanged The file is assumed to be already compressed. Rename the file and try again. - *file* already exists; do you wish to overwrite (y or n)? Respond "y" if you want the output file to be replaced; "n" if not. - gunzip: corrupt input A SIGSEGV violation was detected which usually means that the input file has been corrupted. - *xx.x%* Percentage of the input saved by compression. (Relevant only for **-v** and **-l**.) - \-- not a regular file or directory: ignored When the input file is not a regular file or directory, (e.g., a symbolic link, socket, FIFO, device file), it is left unaltered. - \-- has *xx* other links: unchanged The input file has links; it is left unchanged. See [**ln**(1)](/ln/1.md) for more information. Use the **-f** flag to force compression of multiply-linked files. ## 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 **gunzip** for decompression, **gunzip** detects that there is extra trailing garbage after the compressed data and emits a warning by default. You can use the --quiet option to suppress the warning. ## BUGS In some rare cases, the --best option gives worse compression than the default compression level (-6). On some highly redundant files, **compress** compresses better than **gzip**. ## REPORTING BUGS Report bugs to: bug-gzip@gnu.org\ GNU gzip home page: \\ General help using GNU software: \ ## COPYRIGHT NOTICE Copyright © 1998–1999, 2001–2002, 2012, 2015–2026 Free Software Foundation, Inc.\ Copyright © 1992, 1993 Jean-loup Gailly Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that this permission notice may be stated in a translation approved by the Foundation.