Linux has a useful utility called file which carries out some tests on a specified file and prints the file type once a test is successful. In this short article, we will explain useful file command examples to determine a file type in Linux.
You can run the following command to verify the version of file utility as shown.
$ file -v file-5.33 magic file from /etc/magic:/usr/share/misc/magic
Linux file Command Examples
1. The simplest file command is as follows where you just provide a file whose type you want to find out.
$ file etc
2. You can also pass the names of the files to be examined from a file (one per line), which you can specify using the -f flag as shown.
$ file -f files.list
3. To make file work faster you can exclude a test (valid tests include apptype, ascii, encoding, tokens, cdf, compress, elf, soft and tar) from the list of tests made to determine the file type, use the -e flag as shown.
$ file -e ascii -e compress -e elf etc
4. The -s option causes file to also read block or character special files, for example.
$ file -s /dev/sda /dev/sda: DOS/MBR boot sector, extended partition table (last)
5. Adding the -z options instructs file to look inside compressed files.
$ file -z backup
6. If you want to report information about the contents only not the compression, of a compressed file, use the -Z flag.
$ file -Z backup
7. You can tell file command to output mime type strings instead of the more traditional human readable ones, using the -i option.
$ file -i -s /dev/sda /dev/sda: application/octet-stream; charset=binary
8. In addition, you can get a slash-separated list of valid extensions for the file type found by adding the –extension switch.
$ file --extension /dev/sda
For more information and usage options, consult the file command man page.
$ man file
