Want to win a PS4? Go Premium and enter to win our High-Tech Treats giveaway. Enter to Win

x
?
Solved

Erasing characters using BackSpace

Posted on 1998-10-29
2
Medium Priority
?
1,901 Views
Last Modified: 2006-11-17
I'd like to perform a char-by-char login and password input. How can I display input properly when BackSpace key pressed? The current source is like the following, but it does not erase chars (I don't know how to do this). It should work in Unix, Win32 used for some testing only.

#!/usr/local/bin/perl
#
use Term::ReadKey;
use English;

my $s;

if ($OSNAME =~ /WIN32/i) {
    $ENTER = chr(13);
} else {
    $ENTER = chr(10);
}  

print "Password: ";
readstring($s, "*");
exit;

#**************************************
sub getchar {
    ReadMode 4;
    my $k;
    while(!defined ($k)) {
       $k = ReadKey(-1);
       next if (!defined ($k));
    }
    ReadMode 0;
    return $k;
}

#**************************************
sub readstring {
    my ($str, $passwordchar) = @_;
    my ($s) = "";
    my ($i_char) = "Empty";
    while ($i_char ne $ENTER) {

        $i_char = getchar();

        if (ord($i_char) == 8) {            # BackSpace
            $s = substr($s, 0, length($s)-1);
        } elsif ($i_char ne $ENTER) {
            print (defined $passwordchar ? $passwordchar : $i_char);
            $s .= $i_char;
        } elsif ($i_char eq $ENTER) {
        } else {
            print "Unknown character in line!\n";
        }
    }
    $_[0] = $s . "\n";
    return 0;      # normal completion
}

0
Comment
Question by:dda
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
2 Comments
 
LVL 5

Accepted Solution

by:
b2pi earned 400 total points
ID: 1205810
\b is the backspace char, but it doesn't erase.  So follow it with a space. Try this:

print "asdfasdf\r";
print "asdf";
print "\b \b";

print "\n\n";

Note that this will cause problems if with things like tabs, line feeds, et al.
0
 
LVL 4

Author Comment

by:dda
ID: 1205811
It works!. Thanks a lot.
0

Featured Post

Ask an Anonymous Question!

Don't feel intimidated by what you don't know. Ask your question anonymously. It's easy! Learn more and upgrade.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

I have been pestered over the years to produce and distribute regular data extracts, and often the request have explicitly requested the data be emailed as an Excel attachement; specifically Excel, as it appears: CSV files confuse (no Red or Green h…
In the distant past (last year) I hacked together a little toy that would allow a couple of Manager types to query, preview, and extract data from a number of MongoDB instances, to their tool of choice: Excel (http://dilbert.com/strips/comic/2007-08…
Explain concepts important to validation of email addresses with regular expressions. Applies to most languages/tools that uses regular expressions. Consider email address RFCs: Look at HTML5 form input element (with type=email) regex pattern: T…
Six Sigma Control Plans

618 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question