#!/usr/bin/perl -w
#
use strict;

if($#ARGV < 2) {
        printf("Usage: substitute regexp replacement files...\n");
        printf("example: substitute '#e0e0e0' '#ccffcc' *.html\n");
        exit 0;
}

my $regexp = $ARGV[0];
my $replacement = $ARGV[1];

shift @ARGV;
shift @ARGV;

for(my $i = 0; $i <= $#ARGV; ++$i) {
        my $file = $ARGV[$i];
        my $tmpfile = $file.".substitute.tmp";
        my $changed = 0;
        open(IN, $file) or die "$file: cannot open";
        open(OUT, "> $tmpfile") or die "$tmpfile: cannot open";
        while(<IN>) {
                my $prev = $_;
                if(s/$regexp/$replacement/g) {
                        $changed = 1;
                }
                print OUT;
        }
        close(OUT) or die "$tmpfile: cannot close";
        close(IN) or die "$file: cannot close";
        if($changed) {
                printf("%s\n", $file);
                rename($tmpfile, $file) or die "$tmpfile: cannot rename";
        } else {
                unlink($tmpfile) or die "$tmpfile: cannot unlink";
        }
}