1. Name

cksum [man page] - checksum and count the bytes in a file

2. Synopsis

cksum [FILE]...
cksum [OPTION] 

3. Examples

Create a file file.txt with the following text:

Samba file and printer sharing is supported by  
all Linux Distributions:Suse Linux, Debian
Linux, Mandrake Linux, Red Hat Linux,
Fedora Linux, Gentoo Linux .

$ cksum file.txt 

cksum calculates a cyclic redundancy check (CRC) of an any given file. Users can check the integrity of any file and see if the file has been modified. Use your favorite text editor and remove a "." from the end of the sentence to see that CRC will change.

$ cat file.txt 

$ cksum file.txt