Unix Tip: Comparing files with checksums

By Sandra Henry-Stocker

Unix systems provide numerous ways to compare files. The most common way to verify that you have received or downloaded the proper file is to compute a checksum and compare it against one computed by a reliable source. MD5 is frequently used to compute checksums because it is computationally unlikely that two different files will ever have the same checksum. Similar commands, such as sum and cksum, also compute checksums but not with as much reliability. Let's look at several checksums and see why.