in reply to Large scale search and replace with perl -i

Semi-untested: 
use File::Find;
@ARGV = ();
find sub {
  push @ARGV, $File::Find::name if -f and /\.html$/;
}, ".";
{
  local $^I = ".bak";
  local $/;
  while (<>) {
    if (s/foo/bar/g) { # changes?
      print; # print the new one
    } else { # no changes?  back it out!
      close ARGVOUT; # for windows, not needed on Unix
      rename "$ARGV$^I", $ARGV or warn "Cannot rename for $ARGV$^I: $!
+";
    }
  }
}

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-- Randal L. Schwartz, Perl hacker
Be sure to read my standard disclaimer if this is a reply.

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Re: &bull;Re: Large scale search and replace with perl -i
by BrowserUk (Patriarch) on Apr 20, 2003 at 07:23 UTC

    One small caveat with this neat technique (that I just got bitten by) is that if $^I is set to a wild card (eg. *.bak or orig_*) so that the filename of the backup is edited rather than simply appended, the rename will fail.

    I'll hazard a guess as to your respose to this as

    <merlyn>Don't do that then. {grin}</merlyn>

    but I thought it was worth a mention here :)

    Examine what is said, not who speaks.
    1) When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.
    2) The only way of discovering the limits of the possible is to venture a little way past them into the impossible
    3) Any sufficiently advanced technology is indistinguishable from magic.
    Arthur C. Clarke.
[reply]
      But, that star there doesn't do anything. That would create files named "foo*.bak" and "bar*.bak" from "foo" and "bar". And thus, the rename would undo it just fine.

      Unless you're talking about some local hack to your Perl to make it interpret $^I differently.

      -- Randal L. Schwartz, Perl hacker
      Be sure to read my standard disclaimer if this is a reply.

      update Oh my goodness. A new feature was snuck in to Perl in 5.6, and documented in perlrun but not perlvar.

      My apologies. Wow, I'll have to write a column about it now to remember it. {grin} And I don't recall it in the perldelta from 5.5 to 5.6, or perhaps I considered it un-noteworthy. Yeah, just checked, not in perldelta. No wonder I hadn't noticed it.

      update 2 On further research, 5.4 didn't have the feature, but 5.5 did. And yet it wasn't in 5.5's perldelta. That's why I missed it. I don't always diff the entire manpage set. {sigh} I rely on perldelta.

      update 3 See "Put your inplace-edit backup files into a subdir".

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