Change file dates linux

5 Linux Touch Command Examples (How to Change File Timestamp)

Every file in Linux is associated with timestamps, which specifies the last access time, last modification time and last change time. Whenever we create a new file, or modify an existing file or its attributes, these timestamps will be updated automatically. Touch command is used to change these timestamps (access time, modification time, and change time of a file).

1. Create an Empty File using touch

You can create an empty file using touch command. The following example will create a zero byte new file named tgs.txt.

You can also use -c option to avoid creating new files. If you use -c option, and if a file doesn’t exists, touch will not create the file.

Commands like ls command and find command uses these timestamp information for listing and finding files. You can also create more than 1 files from a single touch command. The following example will create 4 files named a, b, c, and d.

2. Change File’s Access Time using -a

We can change the access time of a file using -a option. By default it will take the current system time and update the atime field. Before touch command is executed:

$ stat tgs.txt File: `tgs.txt' Size: 0 Blocks: 0 IO Block: 4096 regular empty file Device: 801h/2049d Inode: 394283 Links: 1 Access: (0644/-rw-r--r--) Uid: ( 1000/lakshmanan) Gid: ( 1000/lakshmanan) Access: 2012-10-18 23:58:21.663514407 +0530 Modify: 2012-10-18 23:58:21.663514407 +0530 Change: 2012-10-18 23:58:21.663514407 +0530

$ stat tgs.txt File: `tgs.txt' Size: 0 Blocks: 0 IO Block: 4096 regular empty file Device: 801h/2049d Inode: 394283 Links: 1 Access: (0644/-rw-r--r--) Uid: ( 1000/lakshmanan) Gid: ( 1000/lakshmanan) Access: 2012-10-19 00:08:23.559514525 +0530 Modify: 2012-10-18 23:58:21.663514407 +0530 Change: 2012-10-19 00:08:23.559514525 +0530

3. Change File’s Modification Time using -m

The above method can be used to change the mtime of all obj files, when using make utility. NOTE: It is not possible to change the ctime using touch command

4. Explicitly Setting Access and Modification time using -t and -d

Instead of taking the current time-stamp, you can explicitly specify the time using -t and -d options. The format for specifying -t is [[CC]YY]MMDDhhmm[.SS]

• CC – Specifies the first two digits of the year
• YY – Specifies the last two digits of the year. If the value of the YY is between 70 and 99, the value of the CC digits is assumed to be 19. If the value of the YY is between 00 and 37, the value of the CC digits is assumed to be 20. It is not possible to set the date beyond January 18, 2038.
• MM – Specifies the month
• DD – Specifies the date
• hh – Specifies the hour
• mm – Specifies the minute
• SS – Specifies the seconds

$ touch -a -m -t 203801181205.09 tgs.txt

Verify the above change using stat command:

$ stat tgs.txt File: `tgs.txt' Size: 3 Blocks: 8 IO Block: 4096 regular file Device: 801h/2049d Inode: 394283 Links: 1 Access: (0644/-rw-r--r--) Uid: ( 1000/lakshmanan) Gid: ( 1000/lakshmanan) Access: 2038-01-18 12:05:09.000000000 +0530 Modify: 2038-01-18 12:05:09.000000000 +0530 Change: 2012-10-19 00:40:58.763514502 +0530

You can also use a string to change the time

$ touch -d "2012-10-19 12:12:12.000000000 +0530" tgs.txt

For developers, touch command will be really helpful when you are working with Makefiles

5. Copy the Time-stamp from Another File using -r

You can also take a file as a reference, and update the time for other files, so that both file will hold the same time.

The following touch command example will update the time-stamp of file a.txt with the time-stamp of tgs.txt file.

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How can I change ‘change’ date of file?

You cannot change the ctime by ordinary means. This is by design: the ctime is always updated to the current when you change any of the file’s metadata, and there is no way to impose a different ctime. To change the ctime of a file, you need to do one of the following:

• Set the system time to the ctime you want to impose, then touch the file, then reset the system time.
• Modify the kernel to add an interface to change the ctime.
• Access the disk image directly (e.g. with debugfs ) and twiddle the bits on the disk (don’t do it while the filesystem is mounted).

You have the answer on related SO question pointed by jw013, for extX, on unmounted disk :

# Update ctime debugfs -w -R 'set_inode_field /tmp/foo ctime 201001010101' /dev/sda1 # Drop vm cache so ctime update is reflected echo 2 > /proc/sys/vm/drop_caches 

$ NOW=$(date) && date -s «2030-08-15 21:30:11» && touch file.txt && date -s «$NOW»

The ctime of a file is updated when any of the metadata is changed.

$ ls -l x.py -rw-rw-r--. 1 ignacio ignacio 485 Mar 26 2010 x.py $ stat -c %z x.py 2010-03-26 11:57:56.237068175 -0400 $ chown ignacio x.py $ stat -c %z x.py 2012-04-08 15:31:33.682383575 -0400 $ ls -l x.py -rw-rw-r--. 1 ignacio ignacio 485 Mar 26 2010 x.py 

evandrix’s answer excerpted in the next line,
NOW=$(date) && date -s «2030-08-15 21:30:11» && touch file.txt && date -s «$NOW»
needs to be improved as described below :

In some systems like mine, date output doesn’t give a valid format to set with date -s

My system bash shell version : GNU bash, version 5.0.3(1)-release (x86_64-pc-linux-gnu)
My system date command version : date (GNU coreutils) 8.30

My system date command output and setting the date with this format is:

# date Tue 21 Jan 2020 01:36:22 PM +03 # date -s "Tue 21 Jan 2020 01:36:22 PM +03" date: invalid date ‘Tue 21 Jan 2020 01:36:22 PM +03’ 

So it is necessary to improve evandrix answer;
It would be better to assign the NOW variable to the timestamp value
change NOW=$(date) to NOW=$(date +@%s)

 NOW=$(date +@%s) && date -s "2030-08-15 21:30:11" && \ touch file.txt && date -s "$NOW" 

Adding sudo command for non root user

 sudo bash -c 'NOW=$(date +@%s); date -s "2030-08-15 21:30:11"; touch file.txt; date -s "$NOW"' 

 sudo bash -c 'NOW=$(date +@%s); date -s "$2"; touch "$1"; date -s "$NOW"' -- \ "file.txt" "2030-08-15 21:30:11" 

In this way for easy use, the filename and setting date are assigned as arguments at the end of the line.

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Setting creation or change timestamps

Using utimes , futimes , futimens , etc., it is possible to set the access and modification timestamps on a file. Modification time is the last time the file data changed. Similarly, «ctime» or change time, is the last time attributes on the file, such as permissions, were changed. (Linux/POSIX maintains three timestamps: mtime and ctime, already discussed, and ‘atime’, or access time.) Is there a function to set change timestamps? (Where «change» is the attribute modification or ‘ctime’, not modification time ‘mtime’.) (I understand the cyclic nature of wanting to change the change timestamp, but think archiving software — it would be nice to restore a file exactly as it was.) Are there any functions at all for creation timestamps? (I realize that ext2 does not support this, but I was wondering if Linux did, for those filesystems that do support it.) If it’s not possible, what is the reasoning behind it not being so?

@Madhur Ahuja: touch does not have a parameter (at least, my version does not or is not documented to have one) for changing creation or change times. touch will change modification or access times, however.

I see nothing on that page to indicate that touch has the capability to set change timestamps in any way. Note that I’m looking for change timestamps, which are a different beast from modification timestamps. I’ve tried to clarify my post on this point, if this is what is confusing. If it is not, what passage from that page gives you that suggestion?

@Madhur Ahuja: And pardon my unclear post. I will re-read it in a bit, to see if I can improve it once I’ve let myself get unfamiliar with it.

5 Answers 5

For ext2/3 and possibly for ext4 you can do this with debugfs tool, assuming you want to change the ctime of file /tmp/foo which resides in disk /dev/sda1 we want to set ctime to 201001010101 which means 01 January 2010, time 01:01:

Warning: Disk must be unmounted before this operation

# Update ctime debugfs -w -R 'set_inode_field /tmp/foo ctime 201001010101' /dev/sda1 # Drop vm cache so ctime update is reflected echo 2 > /proc/sys/vm/drop_caches 

Information taken from Command Line Kung Fu blog.

@eitan27 AFAIK debugfs will refuse to work if the disk is mounted, given it can harm the data on the disk.

@Eitan: Because you’re changing bytes on disk, not going through the kernel’s VFS cache. So the kernel’s in-memory data could get out of sync with the data structures on disk.

I had a similar issue, and wrote my answer here.

There are essentially two options:

1. Slight change in kernel (code included in link)
2. Change the system clock to the desired ctime, touch the file, then restore current time. (shell script for that included in link).

According to http://lists.gnu.org/archive/html/coreutils/2010-08/msg00010.html ctime cannot be faked (at least it’s not intended to be fakeable):

POSIX says that atime and mtime are user-settable to arbitrary times via the utimensat() family of syscalls, but that ctime must unfakeably track the current time of any action that changes a file’s metadata or contents.

If you just need to change a file’s ctime for some testing/debugging, bindfs might be helpful. It’s a FUSE filesystem which mounts one directory into another place, and can do some transformation on the file attributes. With option —ctime-from-mtime the ctime of each file is the same as its mtime, which you can set with touch -t .

I’m not experienced in that area; but according to unix.stackexchange.com/a/20464 the various standards don’t require file creation time to be stored. Some filesystems store creation time anyway, and it can be accessed with nonstandard ways.

ctime is not create-time but file attributes’ change-time. For example, the file size is such an attribute. Hence if you modify a file, ctime and mtime get altered. So backup tools can rely on ctime , as it cannot be faked (except if you warp the system time).

The easiest way:

1) change System time 2) copy paste a file on another location. 

I tried this on windows 7 and I succeed to change all three timestamps. The stat command on linux shows that all three timestamps are changed.

The script below automates running debugfs . set_inode_field . ctime . in ismail’s answer for many files. It will copy ctime values from files in /media/MYUSER/MYFS/FOO/BAR (recursively) to /media/MYUSER/MYFS2/FOO/BAR , and umount /media/MYUSER/MYFS2 as a side effect. It will work only if the filesystem of /media/MYUSER/MYFS2 is ext2, ext3 or ext4 (because debugfs works only for these filesystems).

mydev2="$(df /media/MYUSER/MYFS2 | perl -ne '$x = $1 if !m@^Filesystem @ and m@([^ ]+) @; END < print "$x\n" >')" cd /media/MYUSER/MYFS find FOO/BAR -type f | perl -ne 'chomp; my @st = lstat($_); if (@st and -f(_)) < s@"@""@g; print "set_inode_field \"/$_\" ctime \@$st[10]\n" >' >/tmp/sif.out sudo umount /media/MYUSER/MYFS2 # Repeat until success. sudo debugfs -w -f /tmp/sif.out /dev/"$mydev2" 

It handles filenames with whitespace and special characters correctly.

It works independently of time zones. As a limitation of debugfs, its precision is seconds, it ignores anything smaller (e.g. milliseconds, microseconds, nanoseconds). Depending the version of debugfs used, it may use 32-bit timestamps, thus it works correctly with dates before 2038-01-19.

If the current user doesn’t have enough read permissions for /media/MYUSER/MYFS , then the commands above should be run as root ( sudo bash ).

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