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From: dce@mips.UUCP (David Elliott)
Newsgroups: comp.unix.wizards
Subject: Re: #! magic number
Message-ID: <488@quacky.UUCP>
Date: Mon, 29-Jun-87 09:26:48 EDT
Article-I.D.: quacky.488
Posted: Mon Jun 29 09:26:48 1987
Date-Received: Tue, 30-Jun-87 06:28:33 EDT
References: <a7879@brl-adm.ARPA>> <2211@bunker.UUCP> <1097@mtune.ATT.COM> <7180@mimsy.UUCP> <1788@ttrdc.UUCP>
Reply-To: dce@quacky.UUCP (David Elliott)
Organization: MIPS Computer Systems, Sunnyvale, CA
Lines: 47

In article <1788@ttrdc.UUCP> levy@ttrdc.UUCP (Daniel R. Levy) writes:
>In article <7180@mimsy.UUCP>, chris@mimsy.UUCP (Chris Torek) writes:
>< And indeed, it does more:
>< 	% egrep uucp:: /etc/passwd
>< 	uucp::16:16:UNIX-to-UNIX Copy:/usr/spool/uucppublic:/usr/lib/uucp/recording
>< 	% cat /usr/lib/uucp/recording
>< 	#! /bin/awk NR > 1 { print }
><		[message] 
>This is like using a cannon to kill a gopher.
>Why not
>
>/bin/cat << !
>	[message]
>!
>which will also work on systems other than "Berserkeley" UNIX.

What? You mean that your /etc/password will allow you to put multiple
lines in the shell field? What you suggest is that

	uucp::16:..:/bin/cat << !
		[message]

is a valid entry in the password file.

The point was that with #! you can use shell scripts or any other
scripts as login shells or anywhere an executable program can go.
Sure, you could say

	#!/bin/sh
	/bin/cat << !
		[message]
	!

and have it work, but you could not simply say

	/bin/cat << !
		[message]
	!

and have it work unless login(1) executes the script vi sh.

The fact that #!/bin/awk or #!/bin/sed or #!/usr/ucb/tail +2 will
work is due to the generality of the #!, and generality is a big
win.

-- 
David Elliott		{decvax,ucbvax,ihnp4}!decwrl!mips!dce