From: "Bart Schaefer" <schaefer@candle.brasslantern.com>
To: zsh-users@sunsite.auc.dk
Subject: Fun zsh trick for today
Date: Sat, 10 Jun 2000 22:50:51 +0000 [thread overview]
Message-ID: <1000610225052.ZM32045@candle.brasslantern.com> (raw)
Some of you are probably familiar with Perl's "grep" function; given a
regular expression and an array, it returns all the elements of the array
that match the expression. A common Perl idiom is
open(FILE, "<somefile");
@result = grep(/pat/, <FILE>);
Where <FILE> slurps somefile into memory as an array of lines.
Did you know that zsh can do that, too?
If you load the mapfile module:
zmodload -i zsh/mapfile
Then you can write Perl's open(FILE, "<somefile") as
$mapfile[somefile]
And you can write <FILE> as
${(f)mapfile[somefile]}
with the caveat that blank lines are stripped out.
(If you're using zsh 3.0.x or can't load the mapfile module, you can do the
same thing with "${(f)$(<somefile)}". It's just not quite as efficient,
and you have to remember to use the double quotes around it.)
You can write grep(/pat/, array) as
${(M)array:#*pat*}
with the caveat that pat is a glob pattern -- but with extendedglob set,
zsh's glob patterns are full regular expressions, although with a non-sed-
like syntax because of the different special meaning of '*'.
So finally, @result = grep(/pat/, <FILE>) is
result=(${(M)${(f)mapfile[somefile]}:#*pat*})
Try, for example, ${(M)#${(f)mapfile[ChangeLog]}:#*Sven*} to see that there
are 1023 mentions of Sven's name in zsh's ChangeLog file. (I only managed
265 "Bart"s; in fact, there are only 475 lines with the word "zsh"!)
--
Bart Schaefer Brass Lantern Enterprises
http://www.well.com/user/barts http://www.brasslantern.com
Zsh: http://www.zsh.org | PHPerl Project: http://phperl.sourceforge.net
next reply other threads:[~2000-06-10 22:51 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2000-06-10 22:50 Bart Schaefer [this message]
[not found] <no.id>
2000-06-14 13:43 ` Matthias Kopfermann
2000-06-14 13:57 ` Clint Adams
2000-06-14 14:09 ` Ollivier Robert
2000-06-14 15:02 ` Fletch
2000-06-14 14:15 ` Peter Stephenson
2000-06-14 14:21 ` Peter Stephenson
2000-06-14 14:27 ` Clint Adams
2000-06-14 14:37 ` Bart Schaefer
2000-06-14 15:33 ` Matthias Kopfermann
2000-06-14 15:52 ` Peter Stephenson
2000-06-14 16:31 ` Matthias Kopfermann
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