Touch (command): Difference between revisions

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	==Overview==		==Overview==
	A touch utility appeared in Version 7 AT&T UNIX. The version of <tt>touch</tt> bundled in ] ] was written by Paul Rubin, Arnold Robbins, Jim Kingdon, and David MacKenzie.		A touch utility appeared in ] ]. The version of <tt>touch</tt> bundled in ] ] was written by Paul Rubin, Arnold Robbins, Jim Kingdon, and David MacKenzie.

	The ] (SUS) specifies that <tt>touch</tt> should change the access times, modification times, or both, for a file. The file is identified by a pathname supplied as a single argument. It also specifies that if the file identified does not exist, the file is created and the access and modification times are set as specified. If no new timestamps are specified, <tt>touch</tt> uses the current time.		The ] (SUS) specifies that <tt>touch</tt> should change the access times, modification times, or both, for a file. The file is identified by a pathname supplied as a single argument. It also specifies that if the file identified does not exist, the file is created and the access and modification times are set as specified. If no new timestamps are specified, <tt>touch</tt> uses the current time.

Revision as of 18:31, 5 January 2019

touch
Developer(s)	Paul Rubin, Arnold Robbins, Jim Kingdon, David MacKenzie, Kris Heidenstrom
Operating system	Unix and Unix-like, AROS, OS-9, FreeDOS
Type	Command

In computing, touch is a command in Unix and Unix-like operating systems used to update the access date and/or modification date of a computer file or directory. The command is also available in the AROS shell, the OS-9 shell and for FreeDOS. In its default usage, it is the equivalent of creating or opening a file and saving it without any change to the file contents. Touch avoids opening, saving, and closing the file. Instead it simply updates the dates associated with the file or directory. An updated access or modification date can be important for a variety of other programs such as backup utilities or the make command-line interface programming utility. Typically these types of programs are only concerned with files which have been created or modified after the program was last run. Touch can also be useful for quickly creating files for programs or scripts that require a file with a specific name to exist for successful operation of the program, but do not require the file to have any specific content.

Overview

A touch utility appeared in Version 7 AT&T UNIX. The version of touch bundled in GNU coreutils was written by Paul Rubin, Arnold Robbins, Jim Kingdon, and David MacKenzie.

The Single Unix Specification (SUS) specifies that touch should change the access times, modification times, or both, for a file. The file is identified by a pathname supplied as a single argument. It also specifies that if the file identified does not exist, the file is created and the access and modification times are set as specified. If no new timestamps are specified, touch uses the current time.

Programs that perform similar operations as the Unix touch utility are available for other operating systems, including Microsoft Windows and the classic Mac OS.

The FreeDOS version was developed by Kris Heidenstrom.

References

http://aros.sourceforge.net/documentation/users/shell/index.php
Paul S. Dayan (1992). The OS-9 Guru - 1 : The Facts. Galactic Industrial Limited. ISBN 0-9519228-0-7.
http://www.ibiblio.org/pub/micro/pc-stuff/freedos/files/distributions/1.2/repos/pkg-html/group-util.html
touch for Windows
http://www.ibiblio.org/pub/micro/pc-stuff/freedos/files/distributions/1.2/repos/pkg-html/touch.html

External links

touch – Shell and Utilities Reference, The Single UNIX Specification, Version 4 from The Open Group
examples showing how to use touch

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

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