How to calculates CRC checksum and the byte count for file(s)

cksum prints the CRC checksum for each file along with the number of bytes in the file, and the file name unless no arguments were given.

cksum is typically used to ensure that files transferred by unreliable means have not been corrupted, by comparing the cksum output for the received files with the cksum output for the original files (typically given in the distribution).

The CRC algorithm is specified by the POSIX standard. It is not compatible with the BSD or System V sum algorithms and cksum is more robust.

The only options are --help and --version.
An exit status of zero indicates success, and a nonzero value indicates failure.

Example of using cksum:
Create file with following text:

$ echo "Open source is a development method for software that harnesses the power of distributed peer review and transparency of process." > file.txt

$ cksum file.txt
1121778036 130 file.txt

Here cksum calculate a cyclic redundancy check (CRC) of given file (file.txt). Users can check the integrity of file and see if the file has been modified. use your favorite text editor and remove a "." from the end of the sentence and run cksum again on the same file and observe the difference in the output

$ cksum file.txt
2131559972 129 file.txt
  
Another Example:
cksum can be also be used for checking the bunch of files, first get the checksum of the entire files withing the directory
$ cksum * > /someother/location/cksum.list
Above command generates checksums' file.

Now after transferring the files, run the cksum command on the same sets of file to get the new chksum figure and finally compare these two values to figure out if the files are been tempered or not.

$ cksum * > /someother/location/cksum.list-2
$ diff cksum.list cksum.list-2

cksum also can be used for fast searching for duplicates.

$ cksum *