SyntaxShelf

File type

2 snippets across 2 stacks - Bash & Linux, Regular Expressions

SHBash & Linux

Identify File Type

SH · File Content
Syntax
file [options] file...
Example
file mystery_attachment
file -i database.dump
Output
mystery_attachment: PDF document, version 1.7
database.dump: application/octet-stream; charset=binary

Note file examines the file's content (magic bytes), not the extension. -i outputs MIME type. Useful when you receive a file with no extension or a misleading one.

RXRegular Expressions

File Extension Extraction

RX · Common Patterns
Syntax
/\.([a-zA-Z0-9]+)$/
Example
JS:  'report-final.v2.pdf'.match(/\.([a-zA-Z0-9]+)$/)[1]
Py:  re.search(r'\.([a-zA-Z0-9]+)$', 'archive.tar.gz').group(1)
Output
JS: "pdf"
Py: "gz"

Note Captures only the last extension. For double extensions like .tar.gz, match /\.tar\.gz$/ explicitly or extract both with /\.([a-zA-Z0-9]+(?:\.[a-zA-Z0-9]+)*)$/. Alternatively, use path.extname (Node) or os.path.splitext (Python).

Frequently asked questions

How does Bash & Linux handle file type?
This task is covered in 2 stacks on this page: Bash & Linux, Regular Expressions. The "Identify File Type" snippet in Bash & Linux uses `file [options] file...`.
Which command does the Bash & Linux example use?
The "Identify File Type" snippet uses `file [options] file...`, from the File Content section of the Bash & Linux cheat sheet.
Which stacks cover "file type" on this page?
Bash & Linux, Regular Expressions. Together they hold 2 copy-ready snippets for this task.
Is there anything to watch out for?
Yes. For "Identify File Type": file examines the file's content (magic bytes), not the extension. -i outputs MIME type. Useful when you receive a file with no extension or a misleading one.

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