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touch [-acm] [-r ref_file | -t time | -d date_time] file...
touch [-acm] [time_spec] file...
settime [-f ref_file] [time_spec] file...
The touch utility sets the access and modification times of each file. The file operand is created if it does not already exist.
The time used can be specified by -t time, by -d date_time, by the corresponding time fields of the file referenced by -r ref_file, or by the time_spec operand. If none of these are specified, touch uses the current time.
If neither the -a nor -m options are specified, touch updates both the modification and access times.
A user with write access to a file, but who is not the owner of the file or a super-user, can change the modification and access times of that file only to the current time. Attempts to set a specific time with touch results in an error.
The settime utility is equivalent to touch -c [time_spec] file.
The following options are supported in the touch and settime utilities:
The following options are supported for the touch utility: -a
Changes the access time of file. Does not change the modification time unless -m is also specified.
Does not create a specified file if it does not exist. Does not write any diagnostic messages concerning this condition.
Uses the specified date_time instead of the current time. The option-argument must be a string of the form:
YYYY-MM-DDThh:mm:SS[.frac][tz]or
YYYY-MM-DDThh:mm:SS[,frac][tz]where
YYYY is at least four decimal digits giving the year
MM, DD, hh, mm, and SS are as with -t time
T is either the letter T or a single SPACE character
[.frac] and [,frac] are either empty, or a period (.) or a comma (,) respectively, followed by one or more decimal digits, specifying a fractional second
[tz] is either empty, signifying local time, or the letter Z, signifying UTC. If [tz] is empty, the resulting time is affected by the value of the TZ environment variable
Changes the modification time of file. Does not change the access time unless -a is also specified.
Uses the corresponding times of the file named by ref_file instead of the current time.
Uses the specified time instead of the current time. time is a decimal number of the form:
[[CC]YY]MMDDhhmm[.SS]where each two digits represent the following: MM
The month of the year [01-12].
The day of the month [01-31].
The hour of the day [00-23].
The minute of the hour [00-59].
The first two digits of the year.
The second two digits of the year.
The second of the minute [00-61].
| If YY is: CC becomes: |
| 69-99 19 |
| 00-38 20 |
| 39-68 ERROR |
The following option is supported for the settime utility: -f ref_file
Uses the corresponding times of the file named by ref_file instead of the current time.
The following operands are supported for the touch and settime utilities: file
A path name of a file whose times are to be modified.
Uses the specified time_spec instead of the current time. This operand is a decimal number of the form:
MMDDhhmm[YY]where each two digits represent the following: MM
The month of the year [01-12].
The day of the month [01-31].
The hour of the day [00-23].
The minute of the hour [00-59].
The second two digits of the year. YY is optional. If it is omitted, the current year is assumed. If YY is specified, the year is derived as follows:
| YY Corresponding Year |
| 69-99 1969-1999 |
| 00-38 2000-2038 |
| 39-68 ERROR |
See largefile(5) for the description of the behavior of touch when encountering files greater than or equal to 2 Gbyte ( 2^31 bytes).
See environ(5) for descriptions of the following environment variables that affect the execution of touch: LANG, LC_ALL, LANG, LC_ALL, LC_CTYPE, LC_MESSAGES, and NLSPATH. TZ
Determine the timezone to be used for interpreting the time or date_time option-argument or the time_spec operand.
The following exit values are returned: 0
The touch utility executed successfully and all requested changes were made.
An error occurred. The touch utility returned the number of files for which the times could not be successfully modified.
See attributes(5) for descriptions of the following attributes:
| ATTRIBUTE TYPE ATTRIBUTE VALUE |
| CSI Enabled |
| Interface Stability Committed |
| Standard See standards(5). |
futimens(2), stat(2), attributes(5), environ(5), largefile(5), standards(5)
Users familiar with the BSD environment find that for the touch utility, the -f option is accepted but ignored. The -f option is unnecessary because touch succeeds for all files owned by the user regardless of the permissions on the files.