Change 'source' to '.'

[ukch]

In order to work with non-bash shell

[czerasz]

Does it work with zsh?
I think those lines would need to be adjusted as well.

[ukch]

From the bash documentation:

source is a synonym for dot/period '.' in bash, but not in POSIX sh, so for maximum compatibility use the period.

I don't know about zsh, but if it is POSIX-compliant, it should work. My primary purpose here was in supporting sh-like shells (bash or sh are the default on most servers).