[zwp]

> should have "set -eu" at its second line

Do you have a strong reason to prefer "set" over shebang flags? I have a slight preference for shebang flags so I can deliberately override them from the command line (but it's not a hill I'd die on):

    $ cat foo 
    #!/bin/bash -eu
    cd /nowhere
    echo 'still here'
    $ ./foo 
    ./foo: line 2: cd: nowhere: No such file or directory
    $ bash -c ./foo # thinking about system(3)
    ./foo: line 2: cd: nowhere: No such file or directory
    $ bash +e ./foo # override
    ./foo: line 2: cd: nowhere: No such file or directory
    still here
    $

EDIT: Google's shell style guide has "Executables must start with #!/bin/bash and a minimum number of flags. Use set to set shell options so that calling your script as bash <script_name> does not break its functionality."

https://google.github.io/styleguide/shell.xml?showone=Which_...

[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.