How To Change File Timestamps in Linux

In Linux, managing file timestamps is an essential part of system administration. Whether you need to modify timestamps for backup purposes, to track changes, or for any other reason, Linux provides a simple and effective tool to accomplish this task: the touch command.

In this article, we will explore how to change file timestamps in Linux using the touch command and provide examples for better understanding.

Understanding File Timestamps

Before we dive into the commands, it’s important to understand what file timestamps are. In Linux, there are three types of timestamps associated with a file:

1. Access Time (atime): The time when the file was last read.
2. Modification Time (mtime): The time when the file’s content was last modified.
3. Change Time (ctime): The time when the file’s metadata (like permissions or ownership) was last changed.

Please note that the ctime is not a reliable indicator of file creation time, as it changes whenever the file’s metadata is updated.

The touch Command

The touch command is a standard command used to modify the access and modification timestamps of a file. The syntax of the touch command is as follows:

touch [option]... [file]...

The touch command without any option creates a new file if it does not exist. If the file already exists, it updates the access and modification times to the current time.

Changing the Modification Time of a File

To change the modification time of a file to the current time, simply use the touch command followed by the filename:

touch filename

This command will update the mtime and atime of the file to the current system time.

Setting a Specific Timestamp

To set a specific timestamp, use the -d (or --date) option followed by a string that represents the desired date and time:

touch -d "YYYY-MM-DD HH:MM:SS" filename

The -d option tells touch to parse the following string as a date. For example, to set the timestamp to 2 PM on October 20, 2022, you would use:

touch -d "2022-10-20 14:00:00" filename

Changing Timestamp Relative to the Present Time

You can also change the timestamp relative to the present time. For instance, to set the timestamp to 2 hours ago:

touch -d "2 hours ago" filename

This command will set the mtime and atime of the file to 2 hours before the current time.

Changing Timestamps of Multiple Files

To change timestamps of multiple files, you can use the find command in combination with touch. For example, to change the timestamp of all files in a directory:

find DIRECTORY -exec touch -d "2 hours ago" {} +

This command will set the mtime and atime of all files in the specified directory to 2 hours before the current time.

Conclusion

Managing file timestamps is a crucial aspect of Linux system administration. The touch command offers a simple and effective way to change file timestamps. Remember, altering file timestamps can affect processes like backups and audits, so always proceed with caution.

Whether you’re a seasoned system administrator or a Linux beginner, understanding how to manipulate file timestamps is a valuable skill. With the touch command, you have the power to control your file metadata with precision and ease.