#!/usr/bin/perl -w
# The Most Useful Perl Script Ever
# Recursively does a find and replace on every file in a directory for any
# specified string. Follows all subdirectories too.
# Not original, but I could not find exactly what I wanted elsewhere.
# --Johnnie Odom 3/16/08

no warnings "recursion";	# Stop complaining, Perl.

# Kickoff main below here.
# We take three arguments
#	1) Directory to start in.
#	2) Pattern to find in files.
#	3) What to replace the pattern with.
#
# Call subroutine with the first directory.
# Then go ahead and exit the program when done.

if($#ARGV == 2){	#ARGV is always one less than number of arguments supplied.
	$curpath = $ARGV[0];
	$findVar = $ARGV[1];
	$replaceVar = $ARGV[2];
	&changeindir($curpath);
}

else{
	print "Incorrect number of arguments supplied.\n 
	Argument 1: Directory to start in.\n
	Argument 2: Pattern to find in files.\n
	Argument 3: What to replace the pattern with.\n";
}

# Subroutine that does all the actual work via recursion.
# Take a directory name and look at all files in that subdirectory.
sub changeindir {
	
	# Set the path to our input and add a trailing "/" if it does not exist.
	my($subpath);	# Variable is private for each 
	$subpath = $_[0];
	if($subpath !~ /\/$/)
	{
		$subpath .= '/';
	}
	
	# Grab all filenames in the directory passed to the routine.
	opendir(DIR, $subpath);
	my @files = readdir(DIR);
	closedir(DIR);
	
	# Examine each file.
	foreach my $file (@files) {
		
		# Reject current and higher directory entries.
		if (($file eq "./") || ($file eq "../") || ($file eq ".") || ($file eq "..")){
			print "";
		}
		
		else {
			
			$file = $subpath . $file;	# Get the new proper path.
			
			# If the file is a directory, recurse into it and continue.
			if (-d $file){
				&changeindir($file);
			}
			
			# If the file is a text file, perform find / replace.
			elsif( -T $file){		
				open (IN, "+<$file") or die "Could not open file $file: $!\n";
				my @fileop = <IN>;
				seek IN,0,0;
				foreach my $fileop (@fileop){
					$fileop =~ s/$findVar/$replaceVar/g;
					print IN $fileop;
				}
				close IN;
			}
		}
	}
}
# Feel free to add print statements for logging and debugging where needed.