mjhjmtu

I am wondering if we need to add shell title:

#!/bin/bash

on a script, second.sh, which only defines a function, and is called from another script, script.sh.

For example, with script.sh containing

#!/bin/bash

source second.sh

func1 "make amerika great again "

echo $I_AM_SAY

and second.sh containing only a function that is called from the first script:

X=soon

function func1 
 fun=$1
I_AM_SAY=$fun$X

Do we need to define second.sh instead as:

#!/bin/bash
X=soon

function func1 
 fun=$1
I_AM_SAY=$fun$X

or as:

#!/usr/bin/env bash

X=soon

function func1 
 fun=$1
I_AM_SAY=$fun$X

No, you don’t need a shebang line: the running shell sources the script directly, it doesn’t start a new shell (which is the whole point of sourcing a script), so neither it nor the kernel need to know which shell to use to run it.

If you want to prevent the second.sh script from being invoked at all, you can add a

#!/usr/bin/false

shebang line.

If you only source the file from another script, the hashbang doesn't get interpreted (it's just a comment there). It might work as a comment for the reader to remind them that the script uses functionality specific to a particular shell, though. Of course, you should mention that in plain text in comments too, since, you do have a description of your script in a comment near the top of the file anyway, right?