Beefy Boxes and Bandwidth Generously Provided by pair Networks
Don't ask to ask, just ask

How can I validate user input?

by Buckaroo Buddha (Scribe)
on May 10, 2000 at 19:40 UTC ( #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


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...


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"; } }

Please (register and) log in if you wish to add an answer

  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.
  • Log In?

    What's my password?
    Create A New User
    and the web crawler heard nothing...

    How do I use this? | Other CB clients
    Other Users?
    Others imbibing at the Monastery: (6)
    As of 2020-09-22 07:53 GMT
    Find Nodes?
      Voting Booth?
      If at first I donít succeed, I Ö

      Results (128 votes). Check out past polls.