Linux File Checksums

we need two scripts for Linux (or, if possible, everything inside the same script) Script 1: we should be able to define a directory (inside the script or as an extension behind the filename "script1 -directory" the script should generate now an MD5 or SH1 checksum for every file inside the directory and subdirectories. Checksums of all files should be saved. Can be done as a text file inside a directory or a .txt file for each file. Whatever is the best. Script 2: we should be able to define a directory (inside the script or as an extension behind the filename "script1 -directory" the script will compare now if files have the same checksum as calculated before with script1. If I file is different we should write the path and filename to the shell Maybe it is possible to have both things inside one script - the script can check if checksums are already calculated, if not it will start the calculation - if checksums are already calculated it will check if they fit