CMP

Section: User Commands (1)
Updated: 1998 September 23
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NAME

cmp (GNU diffutils) - compare two files or byte ranges

SYNOPSIS

cmp [-clsv] [-i NUM] [--help] [--print-chars] [--ignore-initial=NUM] [--verbose] [--quiet] [--silent] [--version] -I FILE1 [FILE2 [RANGE1 [RANGE2]]]

DESCRIPTION

The cmp utility compares two files of any type and writes the results to the standard output. By default, cmp is silent if the files are the same; if they differ, the byte and line number at which the first difference occurred is reported.

In the output, bytes and lines are numbered beginning with one; however, range inputs are zero-based; see below for details. A filename of - represents standard input.

The following options are available:

-c, --print-chars: Output the differing bytes as characters, rather than as octal numbers. Non-printable characters will be shown in form.
-i NUM, --ignore-initial=NUM: Ignore NUM initial characters from each file. This is a synonym for specifying NUM NUM as the two RANGE arguments.
-l, --verbose: Print the byte number (decimal) and the differing byte values (octal) for each difference.
-s, --quiet, --silent: Print nothing for differing files; return exit status only.
-v, --version: Print the diffutils version number.

BYTE RANGES

The two optional arguments RANGE1 and RANGE2 represent byte ranges to compare within the files. Each range can be expressed in several ways:

M+N: Skip M bytes at the beginning of the input, then compare a maximum of N bytes.
M-N, M,N: Skip M bytes at the beginning of the input, and read between bytes M and N, which are both zero-based.

In either case, both M and N are optional and default to beginning and end of file, respectively. In addition, they can be expressed in decimal, octal (0NNN) or hexadecimal (0xNNN) form.

NOTES

The zero-based range numbers may seem inconsistent with cmp output, which is one-based; this is for compatibility with some versions of cmp which allow "skip N bytes" parameters after the filenames; in this context, the N is zero-based.

DIAGNOSTICS

The cmp utility exits with one of the following values:

0: The files or byte ranges are identical.
1: The files or byte ranges are different; this includes the case where one file or range is identical to the first part of the other. In the latter case, if -s has not been specified, cmp writes to standard output that EOF was reached in the shorter file.
>1: An error occurred.

STANDARDS

The cmp utility is expected to be POSIX 1003.2-compliant.

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Time: 21:33:45 GMT, July 06, 2025

CMP