sha1sum:tldr:0cf94

sha1sum: Read a file of SHA1 sums and filenames and verify all files have matching checksums.

sha1sum

$ sha1sum --check ${filename-sha1}

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The command sha1sum --check ${filename-sha1} is used to check the integrity of a file by comparing its SHA-1 checksum with the provided checksum file.

Here is the breakdown of the command:

sha1sum: This is the command that calculates the SHA-1 checksum of a file. It takes a file as input and generates a unique hash value based on its contents.
--check: This option is used to verify the checksum of a file. It takes the provided checksum file and checks if the calculated checksum of the file matches the one specified in the checksum file.
${filename-sha1}: This is a parameter or variable that represents the file name and the SHA-1 checksum file name. It is an example of parameter expansion, where ${variable-name} is replaced with the value assigned to variable-name. In this case, it is expected that filename-sha1 holds the name of the file and the name of the corresponding SHA-1 checksum file.

To explain the command's purpose, imagine you have a file and its corresponding SHA-1 checksum file. The SHA-1 checksum file contains the expected SHA-1 value calculated for the file. By using this command, you can verify if the actual SHA-1 checksum of the file matches the expected checksum. If they match, it means the file hasn't been modified or corrupted. If they don't match, it suggests that the file may have been tampered with or corrupted.

This explanation was created by an AI. In most cases those are correct. But please always be careful and never run a command you are not sure if it is safe.

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