What is the cmp Command in Linux/UNIX?

CMP Command in Linux/UNIX

The cmp command in Linux/UNIX is used to compare two files byte by byte, helping determine whether the two files are identical or not. When used for comparison, cmp reports the location of the first mismatch if differences are found. If the files are identical, cmp display no message and return the prompt.

Syntax:

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

• OPTION: Optional flags that control the behavior of the command.
• FILE1 and FILE2: Filenames of the two files to be compared.
• SKIP1 and SKIP2: Optional number of bytes to skip at the beginning of each file (default is 0).

Example:

$ cmp file1.txt file2.txt

-b (print-bytes): Displays differing bytes in the output when used with -b option.

$ cmp -b file1.txt file2.txt file1.txt file2.txt differ

-i [bytes-to-be-skipped]: Skips a specified number of initial bytes from both files and then compares them.

$ cmp -i 10 file1.txt file2.txt

-i [bytes-to-be-skipped1:bytes-to-be-skipped2]: Skips several bytes separately from each file.

$ cmp -i 10:12 file1.txt file2.txt

-l (list): Prints byte position and byte value for all differing bytes.

$ cmp -l file1.txt file2.txt

-s (silent): Compares files without writing any messages. Exit values: 0 (identical), 1 (different), 2 (error).

$ cmp -s file1.txt file.txt

-n [number of bytes]: Limits the number of bytes to be compared.

$ cmp -n 50 file1.txt file2.txt

--version: Outputs version information and exits.

$ cmp --version

--help: Displays a help message and exits.

$ cmp --help

These options provide flexibility in how the cmp the command operates, allowing users to tailor the comparison based on their specific needs.