touch (command)

touch
	Example of touch usage
Original author(s)	AT&T Bell Laboratories
Developer(s)	Paul Rubin, Arnold Robbins, Jim Kingdon, David MacKenzie, Randy Smith, TSC, Microware, Apple, Digital Research, Novell, Kris Heidenstrom
Initial release	January 1979; 46 years ago
Written in	C
Operating system	Unix, Unix-like, Plan 9, Inferno, FLEX, OS-9, Classic Mac OS, Windows, DR DOS, AROS, FreeDOS, ReactOS, KolibriOS, IBM i
Platform	Cross-platform
Type	Command
License	coreutils: GPLv3+; FreeDOS: GPLv2; ReactOS: BSD-4-Clause; BusyBox: GPL-2.0-only; Toybox: 0BSD; Plan 9: MIT License

touch is shell command that sets the modification timestamp of an existing file or directory to be current. If the input path does not specify an existing file system item, then it creates a new file at the path.

The Single Unix Specification (SUS) specifies that touch changes the access or modification timestamps, or both. The file is identified by file system path supplied as the sole argument. If the path does not specify a file or directory, the command creates a file with access and modification timestamps as specified or by default to the current time.

By default (no options specified), touching a file is equivalent to creating it with no content or if it exists, opening and saving it without any content changes to update the modification timestamp to be current. This convenience functionality is useful for a variety of scenarios including build and backup. The tools used in such scenarios typically ignore files that are older than a certain point of time. For example make ignores a source code file that is older than the object file it is used to create.

The command is often used to create a new file, so that can subsequently open it in an editor or to create a file required by an operation that does not require specific content.

A command first appeared in Version 7 AT&T UNIX. Today, the command is available for many operating systems, including many Unix and Unix-like systems, Windows (via UnxUtils^[1] and Touch for Windows.^[2]), classic Mac OS, DOS, FreeDOS^[3]^[4], DR DOS 6.0^[5], KolibriOS^[6], FLEX^[7], AROS^[8], OS-9^[9], ReactOS^[10], and IBM i.^[11] The version bundled in GNU Core Utilities was written by Paul Rubin, Arnold Robbins, Jim Kingdon, David MacKenzie, and Randy Smith.^[12]

References

^ "Native Win32 ports of some GNU utilities". unxutils.sourceforge.net.
^ "touch for Windows".
^ "ibiblio.org FreeDOS Package -- touch (Unix-like)". www.ibiblio.org.
^ "ibiblio.org FreeDOS Group -- Utilities". www.ibiblio.org.
^ DR DOS 6.0 User Guide Optimisation and Configuration Tips
^ "Shell - KolibriOS wiki". wiki.kolibrios.org.
^ "FLEX 9.0 User's Manual" (PDF).
^ "AROS Research Operating System". aros.sourceforge.io.
^ Paul S. Dayan (1992). The OS-9 Guru - 1 : The Facts. Galactic Industrial Limited. ISBN 0-9519228-0-7.
^ "reactos/reactos". GitHub.
^ IBM. "IBM System i Version 7.2 Programming Qshell" (PDF). IBM. Retrieved 5 September 2020.
^ "touch(1): change file timestamps - Linux man page". linux.die.net.

External links

touch – Shell and Utilities Reference, The Single UNIX Specification, Version 4 from The Open Group
touch(1) – Linux User Commands Manual
touch(1) – Plan 9 Programmer's Manual, Volume 1
touch(1) – Inferno General commands Manual
examples showing how to use touch

[1] "Native Win32 ports of some GNU utilities". unxutils.sourceforge.net.

[2] "touch for Windows".

[3] "ibiblio.org FreeDOS Package -- touch (Unix-like)". www.ibiblio.org.

[4] "ibiblio.org FreeDOS Group -- Utilities". www.ibiblio.org.

[drdos6userguide-5] DR DOS 6.0 User Guide Optimisation and Configuration Tips

[6] "Shell - KolibriOS wiki". wiki.kolibrios.org.

[7] "FLEX 9.0 User's Manual" (PDF).

[8] "AROS Research Operating System". aros.sourceforge.io.

[9] Paul S. Dayan (1992). The OS-9 Guru - 1 : The Facts. Galactic Industrial Limited. ISBN 0-9519228-0-7.

[10] "reactos/reactos". GitHub.

[11] IBM. "IBM System i Version 7.2 Programming Qshell" (PDF). IBM. Retrieved 5 September 2020.

[12] "touch(1): change file timestamps - Linux man page". linux.die.net.

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v t e Unix command-line interface programs and shell builtins
File system	cat chattr chmod chown chgrp cksum cmp cp dd du df file fuser ln ls mkdir mv pax pwd rm rmdir split tee touch type umask
Processes	at bg crontab fg kill nice ps time
User environment	env exit logname mesg talk tput uname who write
Text processing	awk basename comm csplit cut diff dirname ed ex fold head iconv join m4 more nl paste patch printf read sed sort strings tail tr troff uniq vi wc xargs
Shell builtins	alias cd echo test unset wait
Searching	find grep
Documentation	man
Software development	ar ctags lex make nm strip yacc
Miscellaneous	bc cal expr lp od sleep true and false
Categories Standard Unix programs Unix SUS2008 utilities List

v t e Plan 9 command-line interface programs and shell builtins
File system	chmod chgrp cmp cp dd du file gzip ls mkdir pwd rm split tee touch
Processes	kill ps
User environment	passwd who
Text processing	awk basename comm diff ed eqn join sed sort spell strings tail tr troff uniq wc
Shell builtins	echo test
Networking	ip/ipconfig ip/ping netstat
Searching	grep
Software development	ar hoc lex nm strip yacc
Miscellaneous	bc cal fortune sleep
Category

v t e GNU Core Utilities command-line interface programs
File system	chcon chmod chown chgrp cksum cp dd df dir dircolors install ln ls mkdir mkfifo mknod mktemp mv realpath rm rmdir shred sync touch truncate vdir
Text utilities	b2sum base32 base64 cat cksum comm csplit cut expand fmt fold head join md5sum nl numfmt od paste ptx pr sha1sum shuf sort split sum tac tail tr tsort unexpand uniq wc
Shell utilities	arch basename chroot date dirname du echo env expr factor false groups hostid id link logname nice nohup nproc pathchk pinky printenv printf pwd readlink runcon seq sleep stat stdbuf stty tee test timeout true tty uname unlink uptime users who whoami yes

touch (command)

See also

References

Further reading

External links