"Change, but don't touch" or naive use of perl -pi

Happy-the-monk has asked for the wisdom of the Perl Monks concerning the following question:

Today I found the task to change all occurences of a string in some of a larger sum of files and remembered perlrun, which I don't do very often. After having backupped all files in question (which proved to be a good idea later), I did a

perl -pi -e 's/(:Timeplaner):Projekt,/$1$1,/' *

and naively expected it to change the 115 (out of 432) files that needed the change.

But of course it did more than just that.
All files were changed, and their old access date was lost (read: except for in the backup, d'oh!).

Now I am wondering what would be the nicest way of doing the task to only change those files actually containing the string I am looking for, leaving the others untouched and still use something comparatively simple as perl -pi?

Cheers, Sören

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•Re: "Change, but don't touch" or naive use of perl -pi by merlyn (Sage) on Sep 29, 2004 at 10:49 UTC
Do it in two passes: `my @real; my $target = qr/(:Timeplaner):Projekt,/; while (<>) { if (/$target/) { push @real, $ARGV; close ARGV; } } @ARGV = @real; $^I = ""; while (<>) { s/$target/$1$1,/; print; }` [download] -- Randal L. Schwartz, Perl hacker Be sure to read my standard disclaimer if this is a reply.	[reply] [d/l]
Re: "Change, but don't touch" or naive use of perl -pi by Anonymous Monk on Sep 29, 2004 at 08:47 UTC
Assuming no files with spaces in them: perl -pi -e 's/(:Timeplaner):Projekt,/$1$1,/' `grep ':Timeplaner:Proje +kt,' *` [download]	[reply] [d/l]
Re^2: "Change, but don't touch" or naive use of perl -pi by Happy-the-monk (Canon) on Sep 29, 2004 at 08:52 UTC
that would be `grep -l` to tell `grep` only to list the file names. Yes, there are no spaces in the filenames in question.	[reply]
Re: "Change, but don't touch" or naive use of perl -pi by Your Mother (Archbishop) on Sep 29, 2004 at 21:24 UTC
Probably something like merlyn's double pass is the best approach but it is possible to preserve the file modification times if you want to go about it that way: in-place edit preserving file modification times.	[reply]