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Introduction
The file command in Linux is used to determine the type of a given file. It examines the file content, rather than its extension, to classify the file as a text, executable, archive, image, etc. It is a vital tool for debugging, scripting, and ensuring files are handled correctly in various workflows. file works on virtually all file systems supported by Linux and is a go-to utility for system administrators, developers, and users working with mixed or unknown file types.
The file command is a robust utility that simplifies file type identification in Linux. Its versatility makes it indispensable for troubleshooting, scripting, and daily file management tasks. Share this guide with anyone needing a clear reference to maximize their efficiency with this powerful tool.
Syntax and usage
file [options] <file_name>
Tips for Effective Usage
- Combine with Other Tools: Use file with utilities like
findorxargsto process a large number of files automatically.
find . -type f | xargs file
- Create Reports: Redirect output to a file to generate a report of file types. This is EXTREMELY important if you’re doing filesystem maintenance or working large volumes of data, it’ll help you keep a history of your searches and you can later on parse that history with other tools.
file * > report.txt
- Identify Corrupt Files: since file also lets you analyze the contents of the data, use file to quickly identify files that may not be what they claim (e.g., mislabeled extensions).
Key Options
- -b: Outputs just the file type without the file name.
- -i: Displays the MIME type of the file.
- -f : Reads filenames from a given file (one per line) and outputs their types.
- -L: Follows symbolic links and identifies the target file’s type.
- -s: Examines block or character special files to determine their type.
- –mime: Similar to -i, but shows both MIME type and encoding.
- -z: Inspects compressed files.
- –exclude : Excludes files or directories matching the given pattern.
- –help: Displays help and exits.
file -b example.txt
file -i image.jpg
file -f filelist.txt
file -L symlink
sudo file -s /dev/sda1
file --mime document.pdf
file -z archive.tar.gz
file --help
file -z archive.tar.gz
file --exclude=*.tmp *
Common Usage Examples
Basic File Type Identification
To determine the type of a single file:
file document.txt
Check Multiple Files
To check the type of multiple files:
file file1 file2 file3
Checking MIME Types
For determining the MIME type of files:
file -i video.mp4
Handling Symbolic Links
To identify the target type of a symbolic link:
file -L symlink_to_binary
Processing a List of Files
Use a file containing a list of filenames:
file -f filelist.txt
Inspecting Compressed Files
To identify the contents of a compressed file:
file -z logs.tar.gz
Inspecting Device Files
For identifying device file types:
sudo file -s /dev/sda1
