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cmp

file managementLinux/Unix
The cmp command is one of the most frequently used commands in Linux/Unix-like operating systems. cmp Compare two files byte by byte
See ExamplesView Syntax

Quick Reference

Command Name:

cmp

Category:

file management

Platform:

Linux/Unix

Basic Usage:

cmp [options] [arguments]

Common Use Cases

    Syntax

    cmp [OPTION]... FILE1 [FILE2 [SKIP1 [SKIP2]]]

    Options

    Option Description
    -b, --print-bytes Print differing bytes as ASCII
    -i, --ignore-initial=SKIP Skip first SKIP bytes of both inputs
    -i, --ignore-initial=SKIP1:SKIP2 Skip first SKIP1 bytes of FILE1 and first SKIP2 bytes of FILE2
    -l, --verbose Output byte numbers and differing byte values
    -n, --bytes=LIMIT Compare at most LIMIT bytes
    -s, --quiet, --silent Suppress all normal output, only return exit status
    --help Display help message and exit
    --version Output version information and exit

    Examples

    How to Use These Examples

    The examples below show common ways to use the cmp command. Try them in your terminal to see the results. You can copy any example by clicking on the code block.

    #

    Basic Examples:

    # Compare two files
cmp file1.txt file2.txt
    # Compare silently (only exit status) cmp -s file1.txt file2.txt
    # Compare with verbose output showing all differences cmp -l file1.txt file2.txt
    # Compare and print byte numbers in decimal cmp --print-bytes file1.txt file2.txt

    Advanced Examples:

    # Compare two files but skip the first 10 bytes of each
cmp file1.txt file2.txt 10 10
    # Compare standard input with a file 
    cat file1.txt | cmp - file2.txt
    # Use in a script to check if files are different cmp -s file1.txt file2.txt if [ $? -ne 0 ]; then echo "Files are different" else echo "Files are identical" fi # Compare specific parts of files (skip first 512 bytes of file1) cmp file1.bin file2.bin 512

    Try It Yourself

    Practice makes perfect! The best way to learn is by trying these examples on your own system with real files.

    Understanding Syntax

    Pay attention to the syntax coloring: commands, options, and file paths are highlighted differently.

    Notes

    The cmp command compares two files byte by byte and reports the position of the first difference. Unlike diff, which shows all differences between text files in a human-readable format, cmp performs a binary comparison and is more suitable for comparing non-text files.

    Key points about cmp:

    • By default, it reports only the first difference found
    • With the -l option, it reports all differences
    • If no differences are found, cmp exits silently with status 0
    • If differences are found, the exit status is 1
    • If an error occurs, the exit status is > 1
    • It can compare standard input by using - as the filename
    • You can skip bytes at the beginning of either file for partial comparisons

    Exit status codes:

    • 0: The files are identical
    • 1: The files differ
    • 2: An error occurred (inaccessible file, etc.)

    Common use cases:

    • Checking if binary files are identical
    • Quick verification of file copies
    • Comparing specific portions of files
    • Shell scripts that need to determine if files match

    While diff is preferred for text files and provides more detailed information about differences, cmp is often faster and more appropriate for binary files or when you only need to know if files differ but not how they differ.

    Related Commands

    These commands are frequently used alongside cmp or serve similar purposes:

    join
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    Use Cases

    Learn By Doing

    The best way to learn Linux commands is by practicing. Try out these examples in your terminal to build muscle memory and understand how the cmp command works in different scenarios.

    See ExamplesTry Lab Exercises
    $ cmp
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