#!/usr/bin/perl -w

################################################

# ReplaceOne.pl
# Version 1

# Robert D. Cormia
# UCSC Programming for Bioinformatics II
# October 10, 2003

################################################

# ReplaceOne will replace abc with xyz in a single file
#
# Robert D. Cormia
# October 10, 2003
#
# Write a Perl program called 'ReplaceOne' that will replace
# all occurrences of 'abc' to 'xyz' in a data file called 'data1'
#

use strict;


# read file

my $fname_input = 'data1.txt';
my $fname_output = 'output.txt';
my $line;
my $date;

print "This program will open a text file and convert abc to xyz.";
print "\n";
#
# open file, if open fails call die
#

open(INPUT_HANDLE, "$fname_input") or
		die("open() failed for 'fname'\nReason: $!\n\n");


open(OUTPUT_HANDLE, ">$fname_output") or
		die("open() failed for 'fname'\nReason: $!\n\n");

# If a file is passed as an argument to this script,
# user input will not be expected but the file
# provided will be automatically read. You can
# provide as many files as you want - all of them
# will read in the order they were provided.

# Process one line (change abc to xyz)


while ($line = <INPUT_HANDLE>) {
 	$line =~ s/abc/xyz/g;
	print OUTPUT_HANDLE $line;
}

close(INPUT_HANDLE);

close(OUTPUT_HANDLE);

rename("$fname_output","$fname_input") || die "can't rename outfile.txt";

print "This program has converted abc to xyz.";

__END__

Replaced abc by xyz in data1.txt