Depends on the function. If it's just a super-simple one-liner like that you could create an alias or stick the function in ~/.bashrc (a file that bash loads when it starts).

If you're creating something a bit more meaty, it might make more sense to create its own executable script in ~/bin/ which won't exist by default (it's just a directory) but should be in your path. Remember for this the file will need to be executable (chmod +x filename) and start with a proper #!/bin/bash stanza.

The second route has some clear benefits:

• It's easier to see what's available


• A syntax error won't tank your profile


• You don't need to keep re-sourcing your bash config if you change the script


• It's available to any shell as long as the full path is used or ~/bin/ is in the path for that shell too (which it should be in most cases AFAIK).