# This is more of a code snippet to include in programs.  
# It provides for insert, delete, and change functionality to lines of text
# within given files.  Each of the subroutines takes a set of paramaters to invoke it.
# Text below documents the usage for each of the subroutines
#
# insert_line uses three paramaters, the first of which is the filename to insert a line into,
# the second which is the line after which you want the input inserted into, and the third which
# is the text you want inserted into the file.
#
# search_replace uses three parameters, the first being the filename to be worked on, the second
# being the text to search for, and the third being the text to replace the searched text with.
# 
# delete_line uses two paramaters, the name of the file to delete the text from, and the name of
# the text to strike from the file. Below is invocation of delete_lines function example
#
# my $filename="file"; # the filename
# my $delete="Hello"; #Things to search for to insert after
# my $replace="Goodbye!"; #Thing to insert.
# delete_line($filename,$delete);
#
# to enable searching for perl regular expressions, here is an invocation example:
# my $search=qr{perl regular expressions}; e.g. \d+
 
#Uncomment the code below to call the function
#
#
#This subroutine takes 3 paramaters, 1. the file to edit, 2. the thing to search for, 3. text
# to be inserted after the found item.  It backs up the old file, creates a new file, and then 
#the new file moviing the old file to .bak.
##
sub insert_line {
	my $file=$_[0];  # Name of file to edit
	my $old = $file; # Old file
	my $new = "$file.tmp.$$"; #New File to create
	my $bak = "$file.bak"; #backup of old file
	my $after = $_[1]; #the thing to insert the line after (text)
	my $insertline = $_[2]; #the thing to insert itself
	$old = $file;
	$new = "$file.tmp.$$";
	$bak = "$file.bak";
	open (OLD, "< $old") or die "Can't open $old: $!";
	open (NEW, "> $new") or die "Can't open $new: $!";
	while (<OLD>) {
   		if (/$after/) {
   			$_ .= $insertline;
		}
   		(print NEW $_);
	}	
	close (OLD);
	close (NEW);
	rename ($old, $bak);
	rename ($new, $old);
}
#
#this subroutine changes one thing to another in a file.
#It takes 3 paramaters, The filename, the thing to find, and the thing to replace.
sub search_replace {
	my $file= $_[0];
	my $old = $file;
	my $new = "$file.tmp.$$";
	my $bak = "$file.bak";
	my $find = $_[1];
	my $replace = $_[2];
	open (OLD, "< $old") or die "Can't open $old: $!";
	open (NEW, "> $new") or die "Can't open $new: $!";
	while (<OLD>) {
   		s/$find/$replace/g;
   		(print NEW $_);
	}
	close (OLD);
	close (NEW);
	rename ($old, $bak);
	rename ($new, $old);
}
#
#This subroutine deletes a line in a file.  It takes two arguments, the filename to operate on,
#and line containing the text to be deleted.
#
sub delete_line {
	my $file= $_[0];
	my $old = $file;
	my $new = "$file.tmp.$$";
	my $bak = "$file.bak";
	my $delete = $_[1];
	open (OLD, "< $old") or die "Can't open $old: $!";
	open (NEW, "> $new") or die "Can't open $new: $!";
	while (<OLD>) {
   		if (/$delete/) {
   			$_= "";
		}
   (print NEW $_);
	}
close (OLD);
close (NEW);
rename ($old, $bak);
rename ($new, $old);