Usage
The SUS mandates the following options:
- -a, change the access time only
- -c, if the file does not exist, do not create it and do not report this condition
- -d date_time, use the date_time specified to update the access and modification times
- -m, change the modification time only
- -r file, use the access and modification times of file
- -t time, use the time specified (in the format below) to update the access and modification times
The time is specified in the format yy]MMDDhhmm where MM specifies the two-digit numeric month, DD specifies the two-digit numeric day, hh specifies the two-digit numeric hour, mm specifies the two-digit numeric minutes. Optionally ss specifies the two-digit seconds, cc specifies the first two digits of the year, and yy specifies the last two digits of the year.
Note that if invoked without these options, the standard specifies that the current date and time are used to change the access and modification times. This behaviour simulates an update to a file without having to change it, which may be desirable in certain situations (see the example below).
Other Unix and Unix-like operating systems may add extra options. For example, GNU touch adds a -d option, which enables time input in formats other than that specified.
Note that the dates of creation of symbolic links are not changed .
Read more about this topic: Touch (Unix)
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