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Erasing characters using BackSpace

Posted on 1998-10-29
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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
}

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Question by:dda
2 Comments
 
LVL 5

Accepted Solution

by:
b2pi earned 100 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.
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LVL 4

Author Comment

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

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