The touch command of linux is not commonly used. Generally, it may be used when using make to modify the file timestamp or create a new file that does not exist.
1. Command format:
touch [options]... file...
2. Command parameters:
-a or --time=atime or --time=access or --time=use only changes the access time.
-c or --no-create do not create any documentation.
-d Use the specified datetime instead of the current time.
-f This parameter will be ignored and not processed, and it is only responsible for solving the compatibility problem of the touch command of the BSD version.
-m or --time=mtime or --time=modify only change the change time.
-r Set the date and time of the specified document or directory to be the same as the date and time of the referenced document or directory.
-t Use the specified datetime instead of the current time.
3. Command function:
The touch command parameters can change the date and time of the document or directory, including access time and change time.
4. Usage example:
Example 1: Create a file that does not exist
Order:
touch log2012.log log2013.log
output:
[root@localhost test]# touch log2012.log log2013.log [root@localhost test]# ll -rw-r--r-- 1 root root 0 10-28 16:01 log2012.log -rw-r--r-- 1 root root 0 10-28 16:01 log2013.log If log2014.log does not exist, no file is created [root@localhost test]# touch -c log2014.log [root@localhost test]# ll -rw-r--r-- 1 root root 0 10-28 16:01 log2012.log -rw-r--r-- 1 root root 0 10-28 16:01 log2013.log
Example 2: The time to update log.log is the same as the timestamp of log2012.log
Order:
touch -r log.log log2012.log
output:
[root@localhost test]# ll -rw-r--r-- 1 root root 0 10-28 16:01 log2012.log -rw-r--r-- 1 root root 0 10-28 16:01 log2013.log -rw-r--r-- 1 root root 0 10-28 14:48 log.log [root@localhost test]# touch -r log.log log2012.log [root@localhost test]# ll -rw-r--r-- 1 root root 0 10-28 14:48 log2012.log -rw-r--r-- 1 root root 0 10-28 16:01 log2013.log -rw-r--r-- 1 root root 0 10-28 14:48 log.log
Example 3: Setting the timestamp of the file
Order:
touch -t 201211142234.50 log.log
output:
[root@localhost test]# ll -rw-r--r-- 1 root root 0 10-28 14:48 log2012.log -rw-r--r-- 1 root root 0 10-28 16:01 log2013.log -rw-r--r-- 1 root root 0 10-28 14:48 log.log [root@localhost test]# touch -t 201211142234.50 log.log [root@localhost test]# ll -rw-r--r-- 1 root root 0 10-28 14:48 log2012.log -rw-r--r-- 1 root root 0 10-28 16:01 log2013.log -rw-r--r-- 1 root root 0 2012-11-14 log.log
illustrate:
-t time Use the specified time value time as the new value for the corresponding timestamp of the specified file. Here time is specified as a decimal number of the form: [[CC]YY]MMDDhhmm[.SS]
Here, CC is the first two digits of the number of years, that is, the "century number"; YY is the last two digits of the number of years, that is, the number of years in a century. If no CC value is given, touch will limit the years CCYY to 1969--2068. MM is the number of months, DD is the number of days will limit the number of years CCYY within 1969--2068. MM is the number of months, DD is the number of days, hh is the number of hours (time), mm is the number of minutes, and SS is the number of seconds. The setting range of seconds here is 0--61, so that leap seconds can be handled. The time composed of these numbers is a time in the time zone specified by the environment variable TZ. Times earlier than January 1, 1970 are wrong due to system limitations.