How to perform checksum on a file?
You can use the md5sum or shasum commands.
#md5sum test.txt f1d41356dcabb8d8acefed069b22b0da test.txt
#shasum test.txt 809970aec0109c5464dd36a3a9a5a9e79f838313 test.txt
md5sum is faster if you perform the command on a very large file, but shasum is more secure since the chance of two different files have the same checksum is smaller.