This tutorial explains Linux cmp? command, options and its usage with examples.

cmp - compare two files

DESCRIPTION Compares two files and tells you what line numbers are different.

SYNOPSIS cmp [-c] [-i N] [-l] [-s] [-v] firstfile secondfile

OPTIONS :

-c Output differing bytes as characters.

-i N Ignore differences in the first N bytes of input.

-l Write the byte number (decimal) and the differing bytes (octal) for each difference.

-s Write nothing for differing files; return exit statuses only.

-v Output version info. firstfile

First file that you wish to compare. secondfile Second file that you wish to compare to.

Return values 0  files are identical 1  files differ 2  inaccessible or missing argument

EXAMPLES Two provide examples for this command, lets consider two files :

$ cat file2.txt

My name is Mohak Kataria $ cat file1.txt My name is Mohak 1. Compare file1 to file2 and outputs results $ cmp file1.txt file2.txt file1.txt file2.txt differ: byte 17, line 1 2. Skip same number of initial bytes from both input files $ cmp -i 5 file1.txt file2.txt file1.txt file2.txt differ: byte 12, line 1 So we see that the initial 5 bytes were skipped 3. Skip different number of initial bytes from both input files $ cmp -i 5:2 file1.txt file2.txt file1.txt file2.txt differ: byte 1, line 1 4. Display bytes that differ $ cmp -l -i 5:2 file1.txt file2.txt 1 155 40 2 145 156 3 40 141 4 151 155 5 163 145 7 115 151 8 157 163 9 150 40 10 141 115 11 153 157 12 12 150 cmp: EOF on file1.txt 5. Upper limit on number of bytes to compare $ cmp -l -n 10 -i 5:2 file1.txt file2.txt 1 155 40 2 145 156 3 40 141 4 151 155 5 163 145 7 115 151 8 157 163 9 150 40 10 141 115 Also, we can put a limit on number of bytes to compare. This can be used when we want to compare only a specified number of bytes and not the complete file. This can be achieved through -n option which is followed by the number of bytes.