awk vs. regular expressions starting with equal sign

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4 total messages Started by Henry Spencer Tue, 11 Dec 1984 22:45

#146

Author: Henry Spencer
Date: Tue, 11 Dec 1984 22:45

9 lines
1018 bytes

There is a fundamental lexical ambiguity in awk:  when you see "/=",
is this the divide-by-and-assign operator, or the start of a regular
expression which happens to begin with an equal sign?  Awk thinks it
is the operator, which means you can't start a regular expression with
an equal sign, ever.  To really write such a pattern, you have to resort
to schemes like "/.=/" or "/.*=/".  How annoying.  I can see no real fix.
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry

Re: awk vs. regular expressions starting with equal sign

#148

Author: Charles LaBrec
Date: Thu, 13 Dec 1984 19:20

6 lines
797 bytes

Try /\=/.  It worked for me.

Charles LaBrec
UUCP:		pur-ee!Physics:crl, purdue!Physics:crl
INTERNET:	crl @ pur-phy.UUCP

Re: awk vs. regular expressions starting with equal sign

#150

Author: Jonathan Biggar
Date: Thu, 13 Dec 1984 20:21

12 lines
1322 bytes

In article <4770@utzoo.UUCP> henry@utzoo.UUCP (Henry Spencer) writes:
>There is a fundamental lexical ambiguity in awk:  when you see "/=",
>is this the divide-by-and-assign operator, or the start of a regular
>expression which happens to begin with an equal sign?  Awk thinks it
>is the operator, which means you can't start a regular expression with
>an equal sign, ever.  To really write such a pattern, you have to resort
>to schemes like "/.=/" or "/.*=/".  How annoying.  I can see no real fix.

You should use "/[=]/", it is better.

Jon Biggar
{allegra,burdvax,cbosgd,hplabs,ihnp4,sdccsu3}!sdcrdcf!jonab

Re: awk vs. regular expressions starting with equal sign

#151

Author: Robert Reed
Date: Fri, 14 Dec 1984 23:56

15 lines
1152 bytes

> There is a fundamental lexical ambiguity in awk:  when you see "/=",
> is this the divide-by-and-assign operator, or the start of a regular
> expression which happens to begin with an equal sign? 
>
> 				Henry Spencer @ U of Toronto Zoology
> 				{allegra,ihnp4,linus,decvax}!utzoo!henry

You can easily get around it by escaping it, such as

	awk '/\= / {...}' ...

I tried this on our 4.2BSD system and it seems to work just fine.

-- 
Robert Reed, Logic Design Systems Division, tektronix!teklds!bobr

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