Using a solution to another answer, I added the following to my apache config:
SSLPassPhraseDialog exec:/path/to/passphrase-script
And in that script, I placed this:
#!/bin/sh
echo "put the passphrase here"
Now, when I restart apache, i get the following error:
Invalid command 'echo', perhaps misspelled or defined by a module not included in the server configuration
Should I be using some other command in the shell script? Or do I need to configure apache differently so the echo command works?