I am writing a script that will output an ls command to a file, and compare that file to one that will already exist. I need the script to compare the two files, and output only the lines in the ls that don't appear in the preexisting file. For example, it will ls the programs in /bin, and redirect it to the bindirectory file it will create. It will then check the bindirectory file against one I will have made prior to this, binbase, and take the differences in the two, and output it to the cutdirectories.tmp file. I just need to know how to get only the differing lines.

Take a look at the diff command.

Try something like:

You could use the comm command

I thought diff was a better comm?