Date: Fri, 5 Oct 2001 02:11:56 -0500 From: Mike Meyer <mwm@mired.org> To: Chris Fedde <chris@fedde.littleton.co.us> Cc: questions@freebsd.org, <kory@avatar.com> Subject: Re: Real dumb shell script/awk question Message-ID: <15293.23868.39354.690746@guru.mired.org> In-Reply-To: <32463104@toto.iv>
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Chris Fedde <chris@fedde.littleton.co.us> types:
> On Thu, 4 Oct 2001 17:46:53 -0700 "Kory Hamzeh" wrote:
> +------------------
> |
> | I need to bang together a simple shell script to parse a flat ascii
> | database. The fields are variable width, but each field is separated by the
> | "|" character. Basically, all this script needs to do is to read the
> | database, one line at a line, and if field X is equal to value Y, then print
> | the value of field Z. The user must be able to specify X, Y, and Z on the
> | command line.
> |
> | Now, for the life of me, I can't seem to figure out a simple way of doing
> | this with a bourne shell script. I think awk can do it, but the man pages
> | didn't help me too much with the language. I know other language, like perl,
> | are probably better suited, but I need to customize this script per the
> | clients request, and it will only be needed for a couple of weeks and he'll
> | never need this again.
> |
> | Any tips on how to do this? I'm sure there is a simple way and I'm drawing a
> | blank.
> +------------------
> Awk is your friend
But metacharacters are your enemy.
> $ cat t
> asdf|trew|agfd
> asdf|asdf|435
> wer|asgf|bwhw
> qwert|qewrt|asdf
>
> $ awk -F'|' -e '$1 == $2 {print $3}' t
> 435
That tests field values, not a user-supplied value, and -e isn't an
awk option.
bash-2.05$ cat test
#!/bin/sh
# $1 = X, $2 = Y, $3 = Z
awk -F'|' "\$$1 == $2 {print \$$3}"
bash-2.05$ cat t
asdf|trew|agfd
asdf|asdf|435
wer|asgf|bwhw
qwert|qewrt|asdf
bash-2.05$ sh test 3 435 1 < t
asdf
bash-2.05$
Adding simple argument checking is probably worthwhile, as otherwise
awk complains.
<mike
--
Mike Meyer <mwm@mired.org> http://www.mired.org/home/mwm/
Q: How do you make the gods laugh? A: Tell them your plans.
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