touch — Change the file access and modification times

Format

touch [–acm] [–f agefile] [–r agefile] [–t time] file …

touch [–acm] time file …

Description

The touch command changes certain dates for each file argument. By default, touch sets both the date of last file modification and the date of last file access to the current time. It maintains the correct release times for software and is useful with the make command.

Options

–a: Sets only the access time.
–c: Does not create any file that does not exist. Normally, touch creates such files.
–m: Sets only the modification time.

If you do not specify –a or –m, touch behaves as though you specified both.

To tell touch to use a time other than the current, use one of the following options:

–f agefile

Is an obsolete version of the –r option.

–r agefile

Sets the access and modification times (as indicated by the other options) to those times kept for agefile.

–t time

Specifies a particular time using this format:

[[[[cc]yy]mm]dd]hhmm [.ss]

where:

cc is the first two digits of the year (optional)
yy is the last two digits of the year (optional)
mm is the number of the month (01—12) (optional)
dd is the day of the month (optional)
hh is the hour in 24-hour format (required)
mm is the minutes (required)
ss is the seconds (optional)

An obsolete (but still supported) version of this command lets you omit the –t, but the format is:

[[mm]dd]hhmm[.ss]

or:

mmddhhmmyy[.ss]

Examples

To set the modification time of newfile to the present, enter:
```
touch newfile
```
To set the modification time of oldfile to 13:05 on July 3, 1994, enter:
```
touch –t 9407031305 oldfile
```
To set the modification time of newfile to that of
```
oldfile
```
, enter:
```
touch –r oldfile newfile
```

Environment variables

touch uses the following environment variable:

TZ: Contains the time zone that touch is to use when interpreting times.

Format of the TZ environment variable explains how to set the local time zone with the TZ environment variable.

Localization

touch uses the following localization environment variables:

LANG
LC_ALL
LC_CTYPE
LC_MESSAGES
NLSPATH

See Localization for more information.

Exit values

0

Successful completion

1

Failure due to any of the following:

Inability to access the desired file
Too early a date was specified
Inability to create a file
Inability to change a file's times

2

Failure that resulted in a usage message, including:

Unknown command-line option
Only one of –t, –f, or –r is allowed
–r was missing the agefile
–t was missing its argument
Incorrect date string

Messages

Possible error messages include:

Age file inaccessible: Indicates that time could not be found for the file given with the –f or –r option either because that file does not exist or because the requesting user is not granted the appropriate permission for the file.
Missing age file argument: You specified –f or –r, but did not give a file name after it.
Years earlier than year incorrect: Your system recognizes dates only back to the given year. touch does not accept dates before that time.
Bad date conversion
Only one –r, –f, or –t flag allowed
Missing the date or time argument

Portability

POSIX.2, X/Open Portability Guide, UNIX systems.

Related information

cp, date

Format of the TZ environment variable explains how to set the local time zone with the TZ environment variable.