The Linux file command

Linux file information FAQ: How can I tell what type of file a file is on a Unix or Linux system?

The Linux file command shows you the type of a file, or multiple files. It's usually used when you're about to look at some type of file you've never seen before. When I first started working with Unix and Linux systems I used it a lot to make sure I wasn't about to open a binary file in the vi editor, amongst other things.

You issue the Linux file command just like other commands, like this:

file /etc/passwd

The output of the file command looks something like this:

/etc/passwd: ASCII English text

This is telling you that this is a plain text file. If you use the file command on a gzip'd file, the output will include text like this:

gzip compressed data

If you issue this command on a directory the output will say "directory", a PDF document will be reported as "PDF document", and if you issue it on a special Linux device file (typically under the /dev directory) it will look like this:

/dev/ttyp0: character special (4/0)

You can also issue the Linux file command on more than one file at a time, so you can do this to issue the file command on all files in the current directory:

file *

or this to look at all files in the /etc directory:

file /etc/*

and like this to look at all files in the /dev directory:

file /dev/*