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From: roger@rtech.ARPA (Roger Rohrbach)
Newsgroups: net.unix,net.unix-wizards
Subject: Re: "#! /bin/sh" vs ":"
Message-ID: <374@rtech.ARPA>
Date: Fri, 10-May-85 19:06:39 EDT
Article-I.D.: rtech.374
Posted: Fri May 10 19:06:39 1985
Date-Received: Tue, 14-May-85 23:46:48 EDT
References: <183@ski.UUCP>
Organization: Relational Technology, Berkeley CA
Lines: 22
Xref: watmath net.unix:4501 net.unix-wizards:13160

> But what's really happening here?

	The "#!/bin/sh" trick only works on 4.2BSD and derivatives;
it's actually a magic number for the execve() system call, and is a
generalized way of invoking the correct interpreter for a file.  In
other words, a Franz Lisp program in a file named "prog" which  has
been made executable and which starts with the line:

		#!/usr/ucb/lisp

can be run by typing "prog".
	If you are running csh on a non-BSD Unix system, the  way to
ensure that a file is interpreted by /bin/sh is to make certain that
its first character is not a '#'.  Even a file beginning "#!/bin/sh"
will not be interpreted by sh on such a system, since this is simply
an ordinary comment.  Alternatively, if you set the 'shell' variable
to "/bin/sh", all shell scripts will be interpreted by sh.


						Roger Rohrbach

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