How can I validate user input?

Buckaroo Buddha has asked for the wisdom of the Perl Monks concerning the following question:

I've tried:

$start = $ARGV[0];

if ($start eq '') {
    $start = &get_start_level;
}
sub get_start_level {
    print "Please Enter the Start-Level (0-7,?)[0]: ";    
    $input = <>;
    # clear all but numbers or '?'
    #if ($input ne '?') {
    #    $input =~ tr/!(0-9)//\d;
    #}
    
    if ($input eq '?') {
      print " **** internally coded help information  **** \n";
    print " **** internally coded help information  **** \n";
    $input = &get_start_level;
    } elsif (($input < 0) || ($input > 7)) {
    print "please enter a number that is between Zero and Seven\n";
    $input = &get_start_level; 
    }
    return ($input);
}
  =========================== end code  ============
[download]

This seems to me like a pretty straight forward problem. What am i doing wrong? ... I can't seem to figure this out.

Originally posted as a Categorized Question.

Comment on How can I validate user input? Download Code

Replies are listed 'Best First'.
Re: How can I validate user input? by ton (Friar) on Apr 05, 2001 at 03:56 UTC
`while ($start !~ /^[0-7]$/) { print "Please Enter the Start-Level (0-7,?)[0]: "; $start = <STDIN>; chomp $start; if ($start eq '?') { print "Some help info.\n"; } }` [download]	[reply] [d/l]
Re: how do i work this by Russ (Deacon) on May 12, 2000 at 06:17 UTC
Here's one way to do this: `my $start = $ARGV[0]; while (1){ print "Please Enter the Start-Level (0-7,?)[0]: "; chomp($start = <>); # Check for non-numeric characters if ($start =~ /\D/){ print "\nPlease enter a number (0-7) or ? for help\n"; next; } last if 0 <= $start and $start <= 7; # Check for a help request if ($start eq '?') { print " ** internally coded help information ** \n"; next; } print "\nPlease enter a number between Zero and Seven, inclusive\n"; } print $start;` [download] First, we check that the input is numeric (as you started to do in your commented-out code) to prevent errors if the user enters non-numeric characters. If the input is valid, we just exit the loop. If not, check for a help request and, if not '?', print a generic error message and redo the loop. There are a million different ways to do this, and this is only one of them... Russ	[reply] [d/l]


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