Question

I am working on a cgi script for a number guessing game and I want to store the target value in a readable and writeable file. I don’t know how to do that, but I believe I can use a system() call to do it and some type of expression to extract the value from that file. I need help determining that solution; I have the following already:

#!/usr/bin/perl -w
use CGI qw(:standard);
print header, start_html("Guessing Game"), h2("Guessing game"), "\n";

//need some type of system call to store value if one does not exist 
//or read it if it does (random value generated below)

srand( time() ^ ($$ + ($$ << 15)) );
my $target = int(rand 100) + 1; 

if ( !param() ) {
    print hr, "\n", start_form;
    print p("Try to guess a number between 1 and 100: ", textfield("guess")), "\n";
    print end_form, "\n", hr;
} else {
    print hr, "\n", start_form;
    my $guess = param("guess");
    if ($guess > $target) {
        print p ("$guess is too high; try again: ", textfield("guess")), "\n";
    } elsif ($guess < $target) {
        print p ("$guess is too low; try again: ", textfield("guess")), "\n";
    } else {
        print p ("You got it: $guess!");
        //erase value from file
    }
print end_form, "\n", hr;
}
print end_html, "\n";

Answer 1

Use open to open a file.

use strict;

# Get number
open(my $infh, '<', '/path/to/file') or die "Cannot open: $!";
my $number = <$infh>;
close($infh);
chomp($number); # removes newline, just in case

# Save number
open(my $outfh, '>', '/path/to/file') or die "Cannot open: $!";
print $outfh $number;
close($outfh);