---
name: "cmp"
section: "1"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["linux", "freebsd", "openbsd", "macos"]
url: "https://new.carta.tech/cmp"
---

# cmp(1)

compare two files

## NAME

**cmp** – compare two files

## SYNOPSIS

**cmp** \[**-l** \| **-s** \| **-x**\] \[**-bhz**\] \[**--ignore-initial****=***num1*\[:num2\]\] \[**--bytes****=***num*\] *file1* *file2* \[*skip1* \[*skip2*\]\]

## 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.

Bytes and lines are numbered beginning with one.

The following options are available:

- **-b**, **--print-bytes**

  Print each byte when a difference is found.

- **-h**

  Do not follow symbolic links.

- **-i** *num1*\[:num2\], **--ignore-initial=***num1*\[:num2\]

  Skip *num1* bytes from *file1*, and optionally skip *num2* bytes from *file2*. If *num2* is not specified, then *num1* is applied for both *file1* and *file2*.

- **-l**, **--verbose**

  Print the byte number (decimal) and the differing byte values (octal) for each difference.

- **-n** *num*, **--bytes=**num

  Only compare up to *num* bytes.

- **-s**, **--silent**, **--quiet**

  Print nothing for differing files; return exit status only.

- **-x**

  Like **-l** but prints in hexadecimal and using zero as index for the first byte in the files.

- **-z**

  For regular files compare file sizes first, and fail the comparison if they are not equal.

The optional arguments *skip1* and *skip2* are the byte offsets from the beginning of *file1* and *file2*, respectively, where the comparison will begin. The offset is decimal by default, but may be expressed as a hexadecimal or octal value by preceding it with a leading \`\`0x'' or \`\`0''.

*skip1* and *skip2* may also be specified with SI size suffixes.

## EXIT STATUS

The **cmp** utility exits with one of the following values:

- 0

  The files are identical.

- 1

  The files are different; this includes the case where one file is identical to the first part of the other. In the latter case, if the **-s** option has not been specified, **cmp** writes to standard error that EOF was reached in the shorter file (before any differences were found).

- \>1

  An error occurred.

## EXAMPLES

Assuming a file named *example.txt* with the following contents:

```
a
b
c
```

Compare stdin with *example.txt*:

```
$ echo -e "a\nb\nc" | cmp - example.txt
```

Same as above but introducing a change in the third byte of stdin. Show the byte number (decimal) and differing byte (octal):

```
$ echo -e "a\nR\nc" | cmp -l - example.txt
     3 122 142
```

Compare file sizes of *example.txt* and */boot/loader.conf* and return 1 if they are not equal. Note that **-z** can only be used with regular files:

```
$ cmp -z example.txt /boot/loader.conf
example.txt /boot/loader.conf differ: size
```

Compare stdin with *example.txt* omitting the first 4 bytes from stdin and the first 2 bytes from *example.txt*:

```
$ echo -e "a\nR\nb\nc" | cmp - example.txt 4 2
```

## SEE ALSO

[diff(1)](/diff/1.md), [diff3(1)](/diff3/1.md)

## STANDARDS

The **cmp** utility is expected to be IEEE Std 1003.2 (“POSIX.2”) compatible. The **-b**, **-h**, **-i**, **-n**, **-x**, and **-z** options are extensions to the standard. *skip1* and *skip2* arguments are extensions to the standard.

## HISTORY

A **cmp** command appeared in Version 1 AT&T UNIX.

## BUGS

The phrase “SI size suffixes” above refers to the traditional power of two convention, as described in [expand\_number(3)](/expand_number/3.md).