Need to change, oh, every file at once?

[z3d]

Had a boss show me this one once and it really opened my eyes up. I just never paid attention to those "other" switches you could add to the shebang. What he showed me is a way to combine a two line perl script to a find to change every single file in a directory structure at once (The actual scenario was we had a client lose their hostname through shear incompetence and we had to compensate with what they could get from internic - and we needed to change every file in their web site simultatneously because they also had a practice of hardocding URL's into their site - if it isn't complex, it isn't life...).

OK, here's the code, followed by the explanation...

#!/usr/bin/perl -pi
$_ =~ s/sometext/someothertext/mg;

Yeah, that's the whole script. The secret is in the -pi. Check out the perldoc perl pages for more information - this form replaces the page entriley. You can also set it so perl writes a backup file as it goes too. To use the script, just do a find exec, like so:

find ./ -name "*" -type f -exec ./somescript.pl {} \;

Believe me, this has been a lifesaver. Like moving netscape server instances between servers so you don't have to retweak....

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Zed? Zed's dead, baby, Zed's dead.

[BazB]

A slight modification on this is the following line shell script/perl one-liner that came from a short discussion on the LUG for an easy way to change email addresses in every page on my site:

for i in *.html;
do perl -wpi.bak -e 's/oldusr\@olddomain/newusr\@newdomain/g' $i;
done

I think I can say this is the first snippet that made me think - wow! Perl rocks! :-)
I'm sure TMTOWTDI, but I still press this code into service now and again.

[ariels]

This way of using `find' is inefficient: it spawns a new Perl process for every file processed. Why not use xargs? (Also, ``-name "*"'' does nothing, so you could just lose it)

find ./ -type f | xargs ./somescript.pl

starts the least number of processes. More than one process may be started if the length of the command line grows beyond what's permitted.

[belg4mit]

-name * is redundant with GNU find, other finds such as Solaris require this.

UPDATE: Sorry, Sun requires a PATH which is optional for GNU.

--
perl -pe "s/\b;([st])/'\1/mg"

[belg4mit]

Congratulations, you can make toast!

Not to discourage you in anyway, but this is a very well-known idiom. Very cool, and also one of the things I enjoyed when I first encountered perl. Something that might come in handy with this if you have not yet seen it is File::Find

--
perl -pe "s/\b;([st])/'\1/mg"

[sheriff]

If you wanna be *REALLY* cool using Perl on the command line, have a play with PPT, that replaces common unix-esque utilities with perl equivs.

http://sourceforge.net/projects/ppt <- PPT on sourceforge.

[z3d]

I know this is quickly going off topic, but is PPT still active? Fun idea, but the CVS is over a year old. Unless (gasp) they finished what they set out to do...

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"I have never written bad code. There are merely unanticipated features."