Cmp Command: Compare Files
The cmp command is a powerful utility for comparing two
files byte by byte. It is particularly useful for identifying the
exact location of the first difference between files, which is
crucial for debugging, verifying data integrity, or understanding
changes between versions.
Basic File Comparison
To output the byte and line number of the first difference found
between two files, use the basic cmp command:
cmp <path/to/file_1> <path/to/file_2>Detailed Byte Comparison
To see the first differing character between two files, employ the
-b option:
cmp -b <path/to/file_1> <path/to/file_2>Verbose Difference Output
For a comprehensive view of every difference between two files,
including byte values and character representations, use the
--verbose flag in conjunction with -b:
cmp -b --verbose <path/to/file_1> <path/to/file_2>Comparing Files After a Specific Byte Offset
If you need to start the comparison after a certain number of bytes,
use the -i option. For instance, to compare files
starting after the first 100 bytes:
cmp -i 100 <path/to/file_1> <path/to/file_2>Limiting the Number of Bytes to Compare
To restrict the comparison to a specific number of bytes, use the
-n option. This is useful for performance or when you
only need to check a portion of large files:
cmp -n 200 <path/to/file_1> <path/to/file_2>Silent Comparison with Exit Status
For scripting or automated checks where you only need to know if
files differ (without any output), use the
--quiet flag. The exit status will indicate the result
(0 for identical, 1 for different, 2 for errors):
cmp --quiet <path/to/file_1> <path/to/file_2>Understanding Cmp Exit Codes
- 0: Files are identical.
- 1: Files differ.
- 2: Trouble encountered (e.g., file not found, permission denied).