GPG symmetric encryption: Passphrase on command line

Problem:

You want to use GnuPG’s –symmetric encryption, but instead of interactively entering the password you want to use a command line argument with the cleartext password.

Solution

Use --batch --yes --passphrase <passphrase>:

gpg --symmetric --batch --yes --passphrase 12345 <input file>

Note that this is potentially insecure as it’s way easier to find out the command line parameters of running programs than intercepting the inputs of the interactive input dialog. Therefore, use this strategy only if neccessary.