Open Source

Tech Tip: Determine file size with du

There are times when you'll need to figure out the size of files or directories on your Linux system. This is especially important when you're trying to determine if a certain set of files or directories will fit on a particular backup medium.

The best tool to obtain this information is du, which is available on every Linux system. du is flexible and offers a variety of options. For example, it allows you to determine the size of the current directory and all subdirectories:

$ du -sh

Using du by itself displays the size of every subdirectory under the current directory—it summarizes and reports the data in human-readable format, such as 402 MB instead of 411012 bytes. You can also see the size of every file in every subdirectory by incorporating the "-a" option:

$ du -ah

In addition, you can use du in combination with grep to find a particular file size. If you're searching in a directory and suspect a file is growing extremely large, reduce the output of du to all files and directories 1 GB in size or larger with this command:

$ du -ah|grep -e '[0-9]G'

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