Have you ever downloaded a file from internet. Most files in the internet will be hosted in multiple mirrors. The possibility of the download file to be tampered cannot be ruled out. So it is always advised to checksum your file. I used sha256sum but how do i compare. harish@harish-hp:~/Downloads$ sha256sum ideaIC-2016.3.5.tar.gz | grep '85da1e81036968c272b66f6e4d62c117455352ebc769692742a6abfc97ecbc6c' Output : 85da1e81036968c272b66f6e4d62c117455352ebc769692742a6abfc97ecbc6c ideaIC-2016.3.5.tar.gz ↟However use grep to compare the two sha256sum output. if you are able to grep the expected key then it matches. If there is no output then the key does not matches.