Use of Touch Command

List of Topics

1) About Touch Command and its uses

2) Available time stamp's

3) How to Check time stamp of a file

4) Command line options to modify time stamp

1) About Touch Command and its uses

Everyone is aware that “touch” is the command to create an empty file but apart from that touch command is mainly used to change the time stamp's of the file.

2) Available Time stamp's

Every file/folder in linux has below three time stamps

a) Last access time

b) Last Modification Time

c) Last Change time

Whenever we create a file above mentioned time stamp's will be updated automatically.

3) How to check time stamp of a file

We can change the above time stamp's with the help of touch command. 

Before modifying will first see how to check these time stamps. To check these time stamps we need to use "stat" command. An Sample output of stat command.

[XXXX@server2 ~]# stat test_file

  File: `test_file'

  Size: 0               Blocks: 0          IO Block: 4096   regular empty file

Device: fd00h/64768d    Inode: 791598      Links: 1

Access: (0644/-rw-r--r--)  Uid: (    0/    root)   Gid: (    0/    root)

Access: 2017-03-07 02:19:25.612999258 +0530

Modify: 2017-03-07 02:19:25.612999258 +0530

Change: 2017-03-07 02:19:25.612999258 +0530

4) Command line options to modify time stamp

Below are the command line options to be used with touch command to change the access and modification time

Note: It is not possible to change ctime using touch command

(i)  -a  -> To Change access time alone. To Change the access time of the file just execute touch -a <filename>. By default it will take the current time and update the access time

(ii)  -m -> Similar to -a option just use -m to change the file modification time.

(iii) -r   -> This will copy the timestamp from another file eg: touch <file1> -r <file2>

(iv) -t & -d -> this options are used to explicitly change the time to our value.

      Syntax -> touch -t  [[Century]YY]MMDDhhmm[.ss]

                      touch -d  "YYYY-MM-DD hh:mm:ss" <filename>