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From: breck@aimt.UUCP (Robert Breckinridge Beatie)
Newsgroups: comp.unix.questions
Subject: Re: An awk question or two...
Message-ID: <90@aimt.UUCP>
Date: Mon, 14-Sep-87 22:04:48 EDT
Article-I.D.: aimt.90
Posted: Mon Sep 14 22:04:48 1987
Date-Received: Wed, 16-Sep-87 05:38:36 EDT
References: <3931@well.UUCP> <27817@sun.uucp>
Distribution: na
Organization: AIM Technology, Palo Alto, CA
Lines: 33
Keywords: awk ranges
Summary: Another legal pattern

In article <27817@sun.uucp>, guy@sun.uucp (Guy Harris) writes:
> > 	awk -f comline.awk comvar=\"SUB\" ascii.h
> > 
> > 	this is the file comline.awk:
> > 	
> > 	comvar	{ print }
> > 
> 
> "comvar" is not a legal pattern.  A pattern is either a keyword (such as BEGIN
> or END), a relational expression, or a regular expression.  You can't just
> throw a variable name there and expect "awk" to treat that as a regular
> expression that matches all lines that contain that regular expression; "awk"
> doesn't permit that.
> 

Actually, according to: "Awk - A Pattern Scanning and Processing Language"
by Aho Kernighan and Weinberger (Second Edition), "A variety of expressions
may be used as patterns: regular expressions, arithmetic relational expressions,
*string-valued expressions*, and arbitrary boolean combinations of these."  Now
I haven't been able to make use of variables as "string-valued expressions" in
the pattern part of an awk statement, but I haven't been able to find anything
that says they can't be.  In fact in the action part of an awk statement, a
variable is a valid string-valued expression, so shouldn't it also be valid in
the pattern part of the statement?

I think the question boils down to, "How can I force awk to use the value of
the variable: comvar instead of the string that is the variable's name?"  Or
is my interpretation of documentation flawed?  God knows I've been bitten by
my too-liberal interpretation of documentation before.

-- 
Breck Beatie
uunet!aimt!breck