[vog]

Bash is not always /bin/bash. On some systems (BSDs) it is /usr/bin/bash.

So the portable sh'bang line for bash is:

    #!/usr/bin/env bash

And there you can't add "-eu" anymore, because only one argument is possible in sh'bang lines. (/usr/bin/env would try to find an executable named "bash -eu")

So

    #!/usr/bin/env bash
    set -eu

is the more portable approach. However, for "/bin/sh" this should work portably:

    #!/bin/sh -eu

[saghm]

> Bash is not always /bin/bash. On some systems (BSDs) it is /usr/bin/bash.

Nitpick: on every BSD system I've used, it's /usr/local/bin/bash. But I definitely agree that using /usr/bin/env bash is the preferred solution for when you want to use bash (although I don't think it's even installed by default on most BSD's); as an Arch user (where /usr/bin/python is symlinked to python3 rather than python2), I appreciate those who go out of their way to use proper, portable shebangs.