Perl - Learning MySQL - page 535

while(<INPUTFILE>)
{
# Remove the newline at the end of the line
chomp;
# Split the line by commas
my @AnimalsData=split(",", $_);
# Assign the text before the first comma to the name
my $AnimalName=@AnimalsData[0];
# Assign the text between the first comma and the second comma
# (if any) to the count
my $AnimalCount=@AnimalsData[1];
# Add an entry to the Animals hash for this animal name and
# count pair:
$Animals{$AnimalName}=$AnimalCount;
}
close(INPUTFILE);
# Process the data to calculate the total, then write to the output file
my $Total=0;
print OUTPUTFILE "Pet roll call:\n".
"===========\n";
while ((my $Animal, my $Count) = each(%Animals))
{
print OUTPUTFILE "$Animal:\t$Count\n";
$Total+=$Count;
}
print OUTPUTFILE "===========\n".
"Total:\t$Total\n";
We're providing the name of the output file as the second command-line argument
( ARGV[1] ). The interesting part of this program starts from the second open( ) statement;
since we want to write to the file, we add a greater-than ( > ) symbol before the name of
the output file. We also specify the output file handle OUTPUTFILE immediately after the
print command.
If we don't specify an output file handle, program output is sent to the system standard
output, known as STDOUT . This is almost always the display screen. As with STDIN , we
can use STDOUT without needing to explicitly open and close it. We can also print to
standard output by putting STDOUT as the file handle in the print statement:
print STDOUT "$Animal:\t$Count\n";
Since the program output is sent to standard output by default anyway, STDOUT is as-
sumed when no other file handle is specified, and we can safely omit it (as we have in
all our previous scripts):
print "$Animal:\t$Count\n";