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From: jsdy@hadron.UUCP (Joseph S. D. Yao)
Newsgroups: net.unix-wizards
Subject: Re: Redirection quirks: 2>&1 >file  -- vs. --  >file 2>&1
Message-ID: <176@hadron.UUCP>
Date: Mon, 6-Jan-86 09:47:41 EST
Article-I.D.: hadron.176
Posted: Mon Jan  6 09:47:41 1986
Date-Received: Wed, 8-Jan-86 20:13:12 EST
References: <649@watmath.UUCP> <424@well.UUCP> <350@bdaemon.UUCP>
Reply-To: jsdy@hadron.UUCP (Joseph S. D. Yao)
Organization: Hadron, Inc., Fairfax, VA
Lines: 21
Summary: Some interpreted left-right, other right-left.

In article <350@bdaemon.UUCP> carl@bdaemon.UUCP (carl) writes:
>> In article <649@watmath.UUCP> idallen@watmath.UUCP writes:
>> >    $ command 2>&1 >file
>> >    $ command >file 2>&1
>> >These are not equivalent using our 4.2bsd Bourne shell.  (The 2>&1 in the
>> >first line redirects unit 2 to the tty, not to the file.)
>The real explanation for all of this is that once a Bourne shell command
>line has been read (up to \n or ; or & etc.) it is evaluated from right to
>left.  To convince yourself, try
>	foobar=${foo}${bar} foo="hello" bar=" world"
>versus
>	foo="hello" bar=" world" foobar=${foo}${bar} 

Since the '>'s are obviously interpreted left to right, this can't be
universally true.  Apparently, some things are interpreted left-right
and others right-left.  Actually, I would have expected the
assignments to be interpreted in parallel, and so in both they would
have assigned foobar = "".
-- 

	Joe Yao		hadron!jsdy@seismo.{CSS.GOV,ARPA,UUCP}