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How can I validate user input?

( #10974=categorized question: print w/ replies, xml ) Need Help??
Contributed by Buckaroo Buddha on May 10, 2000 at 19:40 UTC
Q&A  > input and output


Description:

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

Answer: how do i work this
contributed by Russ

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;
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

Answer: How can I validate user input?
contributed by ton

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"; } }

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