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When we write shell scripts we do this:


But What if bash is in /usr/bin/? How can we find it in a portable way inside script? I did this, but it gives error:

#!which bash
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up vote 9 down vote accepted

If bash is in the different location you can hash bang it as follows:

#!/usr/bin/env bash

Location for env is pretty standard across the variants.

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A similar arabesque is useful for python scripts: #!/usr/bin/env python – ncmathsadist Feb 19 '12 at 19:43
python, perl and all other scripting languages. – Karlson Feb 19 '12 at 20:02
But this method does have some drawbacks; see this question and this answer. Most systems are going to install bash as /bin/bash (via a symlink if necessary) simply because so many scripts out there have #!/bin/bash. – Keith Thompson Feb 19 '12 at 21:59
There are drawbacks to using either method but the fact that scripts out there use #!/bin/bash doesn't necessarily make them right. – Karlson Feb 20 '12 at 0:57

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