Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!uakari.primate.wisc.edu!aplcen!haven!mimsy!chris
From: chris@mimsy.umd.edu (Chris Torek)
Newsgroups: comp.unix.shell
Subject: Re: command substitution
Message-ID: <27538@mimsy.umd.edu>
Date: 8 Nov 90 06:50:14 GMT
References: <5697@alpha.cam.nist.gov>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 41

In article <5697@alpha.cam.nist.gov> coleman@cam.nist.gov
(Sean Sheridan Coleman X5672) writes:
>I want to write the following independent statements into one line:
>
>set tmp= `awk '{print $7}' /tmp/process.$$`
>set date = `basename $tmp`

Since your syntax above is C shell (and incorrect C shell at that---the
first line sets the variable tmp to nothing, and sets the variable whose
name is produced by the awk command to nothing), the answer is `there is
no way to do it'.

In sh, it is easy:

	date=`basename \`awk '{print $7}' /tmp/process.$$\``

>I really want to do the following:
>
>set date = `basename `awk '{print $7}' /tmp/process.$$``
>
>Unfortuantly, the second set of Grave accent marks for command
>substitution for the basename command will confuse the shell.

Well no; actually, their main function is to confuse *you*. :-)  They
simply close the others.  This is:

	run "basename"
	run ""
	splice output from basename and "" onto both ends of the awk
	set date to the result.

>Is there a way to "qoute" these so that those grave accent (`)
>will be passed down for another layer command substitution?

No; the C shell internals make this impossible.  (There are several
places that assume that backquote expansion happens only to a depth
of one.)  If you somehow manage to trick the `scanner' all you will
get is a broken shell.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 405 2750)
Domain:	chris@cs.umd.edu	Path:	uunet!mimsy!chris