gmssl:tldr:abf90

This command:

gmssl sms4 -d -in ${filename-sms4}

is used to decrypt a file with the SMS4 algorithm using the gmssl utility.

Here is the breakdown of the command:

• gmssl: It is the command-line interface for the gmssl library, which is a collection of cryptographic algorithms and protocols.
• sms4: It specifies the SMS4 symmetric encryption algorithm, also known as the Chinese National Encryption Algorithm.
• -d: It is an option that stands for "decrypt". This flag tells gmssl to perform the decryption operation.
• -in ${filename-sms4}: It specifies the input file for the decryption operation. ${filename-sms4} is a placeholder for the actual filename. You need to replace it with the actual name of the file you want to decrypt.

Therefore, the command is meant to decrypt a file using the SMS4 algorithm with the gmssl utility.