Path: utzoo!mnetor!uunet!husc6!hao!noao!arizona!rupley
From: rupley@arizona.edu (John Rupley)
Newsgroups: comp.unix.questions
Subject: Re: Expansion of variables in sh scripts
Message-ID: <3859@megaron.arizona.edu>
Date: 14 Feb 88 21:04:29 GMT
References: <1159@valhalla.ee.rochester.edu>
Organization: U of Arizona CS Dept, Tucson
Lines: 36
Keywords: Forward quote, backword quote, double quote, auuuuuuuuugh!
Summary: easy to fix, but there's a better way



In article <1159@valhalla.ee.rochester.edu>, badri@valhalla.ee.rochester.edu (Badri Lokanathan) writes:
> Given a 2 column file of data in two columns, the columns separated by
> blanks. A script is desired which, among other things, searches for a
> word in the I column and outputs the corresponding entry in the II column.
> There are several ways of doing this; I want to know why the following
> inconsistency took place (I tried it on BSD4.3):
> #!/bin/sh
> word=$1
> result=`awk "/^${word}/{print \$2}" datafile`
> echo $result
> # This outputs the entire line, rather than the entry in the II column.
> awk "/^${word}/{print \$2}" datafile
> # This outputs only the entry in the II column, as expected.

Unless you escape the escape:
	result=`awk "/^${word}/{print \\$2}" datafile`
                                   >> ^ <<
the shell substitutes a null string for $2, and print by default
sends out the full line.  To watch what happens, run under "sh -x".

But you perhaps should avoid shell substitution inside an awk program.
The following does what I think you want to do, more simply and
less ambiguously:
#!/bin/sh
result=`awk '$1 == word {print $2}' word=$1 datafile`
echo $result
awk '$1 == word {print $2}' word=$1 datafile


John Rupley
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 (H) 30 Calle Belleza, Tucson AZ 85716 - (602) 325-4533
 (O) Dept. Biochemistry, Univ. Arizona, Tucson AZ 85721 - (602) 621-3929