Cheatsheet & Examples: file
The file command identifies the type of a file or files by checking their contents and metadata.
Identify the type of a single file
Example Usage:file filename
What it does:
Determines the type of the specified file, such as text, image, executable, or compressed data.
Command-line Arguments Explained:
filename: The file whose type is to be identified.
Display brief output without filename
Example Usage:file -b filename
What it does:
Shows only the file type information without including the filename in the output, useful for scripting.
Command-line Arguments Explained:
-b: Use brief output (suppresses filename display).filename: The file whose type is to be identified.
Identify the type of multiple files
Example Usage:file file1 file2 file3
What it does:
Checks the file types of all specified files, displaying each result individually.
Command-line Arguments Explained:
file1,file2,file3: List of files to analyze.
Display MIME type information
Example Usage:file -i filename
What it does:
Reports the MIME type (e.g., text/plain, image/jpeg) of the file, which is useful for web and email applications.
Command-line Arguments Explained:
-i: Output the MIME type and subtype.filename: The file to analyze.
Follow symbolic links to check the target file
Example Usage:file -L symlink
What it does:
Resolves symbolic links and checks the type of the file they point to, rather than the link itself.
Command-line Arguments Explained:
-L: Follow symbolic links to their target files.symlink: The symbolic link to evaluate.
Check block or character device files
Example Usage:file -s /dev/device
What it does:
Analyzes the type of special device files (e.g., /dev/null, /dev/sda) such as block or character devices.
Command-line Arguments Explained:
-s: Check block or character device files (requires read access to the device)./dev/device: The device file to analyze.
Read filenames from a list file
Example Usage:file -f list.txt
What it does:
Uses the filenames listed in list.txt to determine their types, processing them one by one.
Command-line Arguments Explained:
-f: Read filenames from the specified file (list.txt).list.txt: A text file containing the names of files to analyze.
Use a custom magic file for classification
Example Usage:file -m /path/to/magicfile filename
What it does:
Overrides the default magic database with a custom one to identify the file type based on user-defined rules.
Command-line Arguments Explained:
-m: Specify the path to a custom magic file./path/to/magicfile: The location of the custom magic database.filename: The file to analyze.
Continue checking after errors
Example Usage:file -k filename
What it does:
Keeps processing other files even if one encounters an error (e.g., permission denied).
Command-line Arguments Explained:
-k: Continue checking after errors.filename: The file to analyze.
