Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!uunet!husc6!cmcl2!beta!dph
From: dph@beta.UUCP (David P Huelsbeck)
Newsgroups: comp.unix.questions
Subject: Re: An awk question or two...
Message-ID: <10025@beta.UUCP>
Date: Mon, 14-Sep-87 12:16:04 EDT
Article-I.D.: beta.10025
Posted: Mon Sep 14 12:16:04 1987
Date-Received: Tue, 15-Sep-87 05:55:22 EDT
References: <3931@well.UUCP> <27817@sun.uucp>
Reply-To: dph@LANL.GOV.ARPA (David P Huelsbeck)
Distribution: na
Organization: Los Alamos Natl Lab, Los Alamos, N.M.
Lines: 74
Keywords: awk ranges
Summary: You can at least do what you want

In article <27817@sun.uucp> guy@sun.uucp (Guy Harris) writes:
>In article <3931@well.UUCP> daniels@well.UUCP (Dan Smith, Social Mammal...) 
> writes:
>> 	awk -f comline.awk comvar=\"SUB\" ascii.h
>> 
>> 	this is the file comline.awk:
>> 	
>> 	comvar	{ print }
>> 
>> 	and, the result:
>> 
 [ usual wonderfully helpful awk error messages deleted ]
>
>"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.

TRUE.

>What you want to do instead is to pass the program to "awk" *on the command
>line*, and put it in double quotes so that shell variables are expanded before
>the string is passed to "awk".  

Maybe, maybe not.

>	Guy Harris

Guy is correct. But if you'll look at my  spreadsheet calculator example
you'll see that in this specific case there is a way to do what you want
to do. I haven't yet figured out a way to do this using real regexs and
pattern matching yet but I'll bet if you use a sufficiently twisted method
you could do it somehow. After all that's the fun of awk. ;-)

Try this:

	#comline.awk (script to do something)
	
	$1 == arg1 , $1 == arg2 {			
		
		if ($1 ~ /-f/) print $2

	}

Then awk -f comline.awk arg1="-ds" arg2="-de" ascii.h

and you get:

bhuff.bin
bhuff.c
dirinfo

The important thing to note here is that whenever you use ~ or !~ one
of the operands must be a true pattern i.e. /regex/
This is too bad but I think it is a result of the fact that awk "compiles"
regexs during the script compilation phase. I suppose it does this for
reasons of speed but I'm not sure enough to say. So while putting $1 == xyz
in the pattern field is OK $1 ~ xyz will cause awk to barf. This is true
everywhere. So "if ($1 ~ "-f") print $2 " will net you a syntax error also.

This is the best AWK solution I could come up with. If you need something
more using the shell variables is the best way I can think of just now.
If you can figure out a way around this limitation without using the shell
I'd like to see it.

	David Huelsbeck
	dph@LANL.GOV
	{cmcl2,ihnp4}!lanl!dph

#include <standard_disclaimers.h>