Content-type: text/html Man page of touch

touch

Section: User Commands (1)
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NAME

touch - Updates file access and modification times  

SYNOPSIS

touch [-acfm] [-r reference_file|-t time] file...

The following older syntax is now maintained for backward compatibility, but may be withdrawn in future issues: touch [-acfm] [time] file...


 

STANDARDS

Interfaces documented on this reference page conform to industry standards as follows:

touch:  XPG4, XPG4-UNIX

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. [Compaq]  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 represent the following: The first two digits of the year (the century) 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 current 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 environment 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 January 2000 UCT.
The range for SS is 00-61 rather than 00-59 because of leap seconds. 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 created.

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 as described for the -t option.
 

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 XPG4 and XPG4-UNIX standards. The -r or -t options should be used.
 

EXIT STATUS

The following exit values are returned: Successful completion. [Compaq]  The number of files whose times could not be successfully modified (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 program.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 .o. The 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 ./, so that the file name is 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: Provides 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 variables contain an invalid setting, the utility behaves as if none of the variables had been defined. If set to a non-empty string value, overrides 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 multibyte characters in arguments). Determines the locale for the format and contents of diagnostic messages written to standard error. [Compaq]  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 location of message catalogues for the processing of LC_MESSAGES. Determines 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)


 

Index

NAME
SYNOPSIS
STANDARDS
OPTIONS
OPERANDS
DESCRIPTION
NOTES
EXIT STATUS
EXAMPLES
ENVIRONMENT VARIABLES
SEE ALSO

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Time: 02:42:50 GMT, October 02, 2010