| cmp | |
|---|---|
| Original authors | Dennis Ritchie (AT&T Bell Laboratories) |
| Developers | Variousopen-source andcommercial developers |
| Initial release | November 3, 1971; 54 years ago (1971-11-03) |
| Written in | Plan 9:C |
| Operating system | Unix,Unix-like,Plan 9,Inferno,OS-9,IBM i |
| Type | Command |
| License | coreutils:GPLv3+ Plan 9:MIT License |
cmp is ashellcommand that compares twofiles of anytype and reports differences. By default, it outputs nothing if the files match. If they differ, it reports thebyte and line number of the first difference. Theexit code can be used programmatically since it is 0 if the files match, 1 if the files differ or 2 if comparison fails (i.e. inaccessible or missing argument).
The command is available onUnix-like systems,OS-9,IBM i andWindows (viaUnxUtils).[1][2][3] The command first appeared inVersion 1 Unix.[4] It is part of theX/Open Portability Guide since issue 2 of 1987. It was inherited into the first version of POSIX.1 and theSingle Unix Specification.[5] The implementation inGNUcoreutils was written by Torbjorn Granlund and David MacKenzie.[6]
Command line options include:
| Option | Description | Unix | Plan 9 | Inferno | FreeBSD | Linux | IBM i |
|---|---|---|---|---|---|---|---|
| -b, --print-bytes | Print the differing bytes; display control bytes as a '^' followed by a letter of the alphabet and precede bytes that have the high bit set with 'M-' (which stands for "meta") | No | No | No | No | Yes | No |
| -h | Do not follow symbolic links | No | No | No | Yes | No | No |
| -i SKIP, --ignore-initial=SKIP | Skip the first SKIP bytes of input | No | No | No | No | Yes | No |
| -i SKIP1:SKIP2, --ignore- initial= SKIP1:SKIP2 | Skip the first SKIP1 bytes of FILE1 and the first SKIP2 bytes of FILE2 | No | No | No | No | Yes | No |
| -l, --verbose | Print the (decimal) byte numbers and (octal) values of all differing bytes, instead of the default info; also, print the EOF message if one file is shorter than the other | Yes | Yes | Yes | Yes | Yes | Yes |
| -L | Print the line number of the first differing byte | Yes | Yes | Yes | No | No | No |
| -n LIMIT, --bytes=LIMIT | Compare at most LIMIT bytes | No | No | No | No | Yes | No |
| -s, --quiet, --silent | Print nothing; yield exit status only | Yes | Yes | Yes | Yes | Yes | Yes |
| -t | Text mode where the files are opened in text mode and translated to theCCSID of the job before comparing byte for byte | No | No | No | No | No | Yes |
| -v, --version | Print version info | No | No | No | No | Yes | No |
| -x | Like -l but prints in hexadecimal and using zero as index for the first byte in the files | No | No | No | Yes | No | No |
| -z | For regular files, compare file sizes first, and fail if they are not equal | No | No | No | Yes | No | No |
| --help | Print command-line help info | No | No | No | No | Yes | No |
Operands that are byte counts are decimal by default, but may be preceded by '0' for octal and '0x' for hexadecimal.
A byte count can be followed by a suffix to specify a multiple of that count; in this case an omitted integer is understood to be 1. A bare size letter, or one followed by 'iB', specifies a multiple using powers of 1024. A size letter followed by 'B' specifies powers of 1000 instead. For example, '-n 4M' and '-n 4MiB' are equivalent to '-n 4194304', whereas '-n 4MB' is equivalent to '-n 4000000'. This notation is upward compatible with the SI prefixes[7] for decimal multiples and with the IEC 60027-2 prefixes for binary multiples.[8]
cmp(1) – FreeBSD General CommandsManualprintf – Shell and Utilities Reference,The Single UNIX Specification, Version 5 fromThe Open Group
cmp: compare two files – Shell and Utilities Reference,The Single UNIX Specification, Version 5 fromThe Open Group| File system | |
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