touch(1)touch(1)NAMEtouch - Updates file access and modification times
SYNOPSIStouch [-acfm] [-r reference_file | -t time] file...
The following older syntax is now maintained for backward compatibil‐
ity, but may be withdrawn in future issues: touch [-acfm] [time]
file...
STANDARDS
Interfaces documented on this reference page conform to industry stan‐
dards as follows:
touch: XCU5.0
Refer to the standards(5) reference page for more information about
industry standards and associated tags.
OPTIONS
Changes only the access time. Suppresses the creation of the file.
[Tru64 UNIX] Attempts to force the touch in spite of read and write
permissions on a file. The -f option is actually a dummy option; it is
not used by the touch code, but is recognized by getopt(). Changes
only the modification time. Uses the time of the file named by the
pathname reference_file instead of the current time. You cannot use -r
and -t together. Uses the specified time instead of the current time.
The time argument is a decimal number in the following form:
[[CC]YY]MMDDhhmm[.SS]
The paired decimal numbers in the preceding syntax line repre‐
sent the following: The first two digits of the year (the cen‐
tury) The second two digits of the year (00-99) 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 of the minute
(00-61)
Both CC and YY are optional. If neither is specified, the cur‐
rent year is assumed. If YY is specified, but CC is not, CC is
derived as follows:
If YY is 69-99, CC is 19.
If YY is 00-68, CC is 20.
The resulting time is affected by the value of the TZ environ‐
ment variable. If the resulting time value precedes the Epoch,
touch exits immediately with an error status. The range of
valid times past the Epoch extends to at least midnight 1 Janu‐
ary 2000 UCT.
The range for SS is 00-61 rather than 00-59 because of leap sec‐
onds. If SS is 60 or 61, and the resulting time, as affected by
the TZ environment variable, does not refer to a leap second,
the resulting time is one or two seconds after a time where SS
is 59. If SS is not given a value, it is assumed to be 0
(zero).
If neither the -a option nor the -m options are specified, touch
behaves as if you have specified both options.
OPERANDS
The file for which times should be modified, or which should be cre‐
ated. If the file is a symbolic link, the link will be traversed and
filename resolution will continue.
In the obsolescent version, if both the -r and -t options are
omitted, and if the first file parameter is an eight or ten
digit decimal integer, it is interpreted as a time parameter.
The format for the time parameter in the obsolesent syntax is
MMDDhhmm[YY]
DESCRIPTION
The touch command updates the access and modification times of each
file or directory named to the one specified on the command line or to
the current time if you do not specify a time. You can specify the
time with -t or by the time of the reference file with the -r option.
If you do not specify a time, touch uses the current time. If you
specify a file that does not exist, touch creates a file with that name
unless you request otherwise with the -c option.
The LC_TIME environment variable, if defined, specifies the order of
month and day in the date specification and of hour and minute in the
time specification. Otherwise, these orders default to MMdd and hhmm.
The format for the time argument is MMddhhmm[yy].
The obsolescent format for the time argument is MMddhhmm[YY].
NOTES
The obsolescent version may be withdrawn from future versions of the
XCU5.0 standards. The -r or -t options should be used.
EXIT STATUS
The following exit values are returned: Successful completion. [Tru64
UNIX] The number of files whose times could not be successfully modi‐
fied (including files that did not exist and were not created).
When the -c option is specified, files are suppressed purposely, an
error does not occur and a message is not written to standard error.
The exit status returns zero (0) for success.
EXAMPLES
To update the access and modification times of a file, enter: touch
program.c
This sets the last access and last modification times of pro‐
gram.c to the current date and time. If program.c does not
exist, touch creates an empty file with that name. To avoid
creating a new file, enter: touch-c program.c To update only
the modification time, enter: touch-m *.o
This updates only the last modification times of the files in
the current directory that end with touch command is often used
in this way to alter the results of the make command. To
explicitly set the access and modification times, enter: touch-c 02171425 program.c
This sets the access and modification dates to 14:25 (2:25 p.m.)
February 17 of the current year. (This assumes that you are
using the default format.) To touch a file with a numeric file
name, include its full pathname or precede it with not mistaken
for the time argument. For example, to touch the file 123.abc
enter: touch-c ./123.abc
ENVIRONMENT VARIABLES
The following environment variables affect the execution of touch: Pro‐
vides a default value for the internationalization variables that are
unset or null. If LANG is unset or null, the corresponding value from
the default locale is used. If any of the internationalization vari‐
ables contain an invalid setting, the utility behaves as if none of the
variables had been defined. If set to a non-empty string value, over‐
rides the values of all the other internationalization variables.
Determines the locale for the interpretation of sequences of bytes of
text data as characters (for example, single-byte as opposed to multi‐
byte characters in arguments). Determines the locale for the format
and contents of diagnostic messages written to standard error. [Tru64
UNIX] This environment variable, if defined, specifies the order of
month and day in the date specification and of hour and minute in the
time specification. Otherwise, these orders default to MMdd and hhmm.
The format for the time argument is MMddhhmm[yy]. Determines the loca‐
tion of message catalogues for the processing of LC_MESSAGES. Deter‐
mines the time zone to be used for interpreting the time specification.
SEE ALSO
Commands: date(1)
Functions: creat(2), utime(2)
Files: locale(4)
Standards: standards(5)touch(1)
