File open, read, write test example

File Handling example from a Well House Consultants training course
More on File Handling [link]

This example is described in the following article(s):
• Good, steady, simple example - Perl file handling - [link]

This example references the following resources:
http://www.wellho.net/course/lpfull.html

Source code: fsv Module: P207

# File open, read, write test example

# Test that the output file won't clobber an old one
# And if that's OK open inputs and outputs

if (-e "file.file") {
        $sz = -s "file.file";
        $tm = -M "file.file";
        print STDERR "Size $sz b, updated $tm days ago\n";
        die "I'm not going to be that brutal\n";
        }
open (FH,"../requests.xyz") or die "No input file\n";
open (FHO,">file.file") or die "Wrong - can't write\n";

# Copy lines including "Perl" to the screen and other lines
# to output file, counting the lines as you do so

$np = $nl = 0;
while ($lyne = <FH>) {
        if ($lyne =~ /Perl/) {
                print "PERL! $lyne";
                $np++;
        } else {
                print FHO $lyne;
        }
        $nl++;
}

# Close both files and report on the work done
# Note that report is supressed if STDOUT redirects to file

close FH;
close FHO;
-t STDOUT and print "Job Completed. Found $np out of $nl\n";

# Finally, provide user documentation through POD!

__END__

This example taught on Well House Consultants
Perl course - written for Delegates on October 2007.
See http://www.wellho.net/course/lpfull.html
graham@wellho.net / +44 (0) 1225 708225

=head1 Example of file handling in Perl

This example program shows the various elements of a
Perl program to tes, open, read and write files.

The file requests.xyz from the parent directory is
opened (if it exists) for input.

The file file.file in the current directory is
opened (if it does NOT exist) for output; if it
already exists, the program exits with an error
message after reporting critical status data.

Data is read line by line and copied from input
to output if it does NOT include the word "Perl";
if it does, the line is echoed to the screen.

Both files are closed, and if the output device
STDOUT is interactive (window rather that file) a
report line of the work done is added.

=cut

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