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PO/usr/bin/env questions regarding shebang line pecularities
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copied!<p><strong>Questions</strong>:</p> <ul> <li>What does the kernel do if you stick a shell-script into the shebang line? </li> <li>How does the Kernel know which interpreter to launch?</li> </ul> <p><strong>Explanation</strong>:</p> <p>I recently wanted to write a wrapper around <em>/usr/bin/env</em> because my CGI Environment does not allow me to set the <em>PATH</em> variable, except globally (which of course sucks!).</p> <p>So I thought, "OK. Let's set PREPENDPATH and set <em>PATH</em> in a wrapper around env.". The resulting script (here called <em>env.1</em>) looked like this:</p> <pre><code>#!/bin/bash /usr/bin/env PATH=$PREPENDPATH:$PATH $* </code></pre> <p>which looks like it should work. I checked how they both react, after setting PREPENDPATH:</p> <pre><code>$ which /usr/bin/env python /usr/bin/env /usr/bin/python $ which /usr/bin/env.1 python /usr/bin/env /home/pi/prepend/bin/python </code></pre> <p>Look absolutely <em>perfect</em>! So far, so good. But look what happens to "Hello World!".</p> <pre><code># Shebang is #!/usr/bin/env python $ test-env.py Hello World! # Shebang is #!/usr/bin/env.1 python $ test-env.1.py Warning: unknown mime-type for "Hello World!" -- using "application/*" Error: no such file "Hello World!" </code></pre> <p>I guess I am missing something pretty fundamental about UNIX.</p> <p>I'm pretty lost, even after looking at the source code of the original <em>env</em>. It sets the environment and launches the program (or so it seems to me...).</p>

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