sum:tldr:98ba0

The command "sum ${filename}" is used to calculate and display the checksum or hash value of a file.

Here's how it works:

1. The command uses the "sum" utility or command-line program to calculate the checksum of the specified file.
2. "${filename}" is a placeholder for the actual name of the file. This means you need to replace "${filename}" with the name of the file you want to calculate the checksum for.
3. The checksum, also known as a hash value, is a unique value generated by applying a specific algorithm (such as CRC32 or MD5) to the contents of the file. The purpose of the checksum is to verify the integrity of the file, as even a small change in the contents will produce a different checksum.
4. The "sum" command will then calculate the checksum and display it on the screen.

Overall, the command "sum ${filename}" is a way to calculate and verify the integrity of a file by computing its checksum or hash value.