md5sum:tldr:6ad95

The command md5sum --check --quiet ${filename-md5} is used to check the validity of a file by comparing its MD5 hash value with a pre-calculated MD5 hash value stored in a file.

Here is a breakdown of the command:

• md5sum: It is a command-line utility that calculates and outputs the MD5 hash value of a file. It is commonly available on Unix-like operating systems.

• --check: This option is used to check the MD5 hash value of a file against a pre-calculated value.

• --quiet: This option is used to make md5sum operate in quiet mode, meaning it does not display any output for individual files.

• ${filename-md5}: This is a parameter or variable that should contain the path or filename of a file that contains the pre-calculated MD5 hash value of the file you want to check. The exact format of the file should be a single line with the MD5 hash value followed by the filename.

So, when you execute md5sum --check --quiet ${filename-md5}, it will read the MD5 hash value and filename from ${filename-md5} file, compare it with the MD5 hash value calculated for the mentioned file, and provide no output (if the hashes match) or an error message (if the hashes don't match).