Three major modification times for Linux files

Linux files have 3 modification times. Many of my friends like to get confused, including me, and are now listed for reference.

1)modification time (mtime, modification time): This time refers to the time when the file content is modified, not the modification of the file attribute. When the data content is modified, this time will change, with the command ls -l defaults to this time:

2)status time (ctime, status time): When the status of a file changes, this time will change, such as changing the permissions and attributes of the file, etc. It will change.

3) access time (atime, access time): When reading the contents of the file, it will change this time, for example, use cat to read /etc/man.config, then the atime of the file will change.

Example:

# ls -l --full-time /etc/man.config mtime

-rw-r--r-- 1 root root 4522 2007 -11-17 18:47:54.000000000 +0800 /etc/man.config

# ls -l --time=atime --full-time /etc/man.config

- Rw-r--r-- 1 root root 4522 2010-03-15 14:20:20.000000000 +0800 /etc/man.config

# ls -l --time=ctime --full-time /etc/man.config

-rw-r--r-- 1 root root 4522 2008-07-11 16:21:55.000000000 +0800 /etc/man.config

- -------------------------------------------------- --------------------------------

#cat /etc/man.config After executing, check again Atime, the time has been changed

# ls -l --time=atime --full-time /etc/man.config

-rw-r--r-- 1 root root 4522 2010-03-15 14:24:30.000000000 +0800 /etc/man.config

Change file permissions: # chmod or /etc/man.config

View ctime, has been changed.

# ls -l --time=ctime --full-time /etc/man.config

-rw-r----- 1 root root 4522 2010-03-15 14:28:34.000000000 +0800 /etc/man.config

If you edit the contents of the file, mtime will change.

If you want to view the three time conditions of the file together, you can use the command stat to view

# stat /etc/man.config

File: `/etc/man .config'

Size: 4522 Blocks: 24 IO Block: 4096 regular file

Device: 807h/2055d Inode: 1049307 Links: 1

Access: (0640/- Rw-r-----) Uid: ( 0/root) Gid: ( 0/root)

Access: 2010-03-15 14:24:30.000000000 +0800

Modify : 2007-11-17 18:47:54.000000000 +0800

Change: 2010-03-15 14:28:34.000000000 +0800

The time is exactly the same as the above time.

The time of the file is very important, because if the file time is misjudged, some programs may not work properly. In case we find a file time is in the future time (many times there will be this problem, we The GMT time mentioned in the installation is that meaning), then how can we make the time become the current time? We only need a touch command.

The usage of touch is:

touch [-actmd] File

Parameter:

-a: Modify only access time

-c: Modify the time only without creating a file

-t: You can pick up the time later. The format is: [YYMMDDhhmm]

-m: Modify only mtime

-d : You can pick up the date later, you can also use --date="date or time"

For example: adjust the date of man.config to two days ago, then:

#touch -d "2 days ago" /etc/man.config

The result atime and mtime will change and ctime will not change.

With the touch command, you can easily change the date and time of the file, and you can also create an empty file, but note that there is no way to copy the ctime attribute even if you copy a file and copy all the property pages.

The commonly used case of the touch command is

1) Creating an empty file

2) Changing the date of a file to the current date (mtime and atime)