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Perl script stopped working

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Top Forums Shell Programming and Scripting Perl script stopped working
# 1  
Old 06-03-2014
Perl script stopped working
Hi,

I have the following segment of a script which is supposed to prompt a user for password and then capture the password entered by the user.

The function is called in by another script and used to work without issue, the problem is that recently the script is not waiting for the user to input the password it and immediately the calling script is giving an error that null password is provided.

Can someone please help?


Code:
sub prompt_for_password
{
  my $account_name = $_[0];
  my $account_description = $_[1];
  my $display_prompt = $_[2];

  if ($display_prompt)
  {
    print STDERR "\n";
    print STDERR "Please enter password for $account_description '$account_name': ";
  }

  $LINUX = -d "/initrd";
  $SOLARIS = -d "/kernel";

  if ($LINUX)
  {
    system "/bin/stty cbreak -echo </dev/tty >/dev/tty 2>&1";
  }

  if ($SOLARIS)
  {
    system "/bin/stty icanon -echo </dev/tty >/dev/tty 2>&1";
  }

  $password = <STDIN>;

  if ($LINUX)
  {
    system "/bin/stty cbreak echo </dev/tty >/dev/tty 2>&1";
  }

  if ($SOLARIS)
  {
    system "/bin/stty icanon echo </dev/tty >/dev/tty 2>&1";
  }

  if ($display_prompt)
  {
    print STDERR "\n";
  }

  chomp($password);

  return $password;
}

# 2  
Old 06-03-2014
Quote:
Originally Posted by belalr
Hi,

I have the following segment of a script which is supposed to prompt a user for password and then capture the password entered by the user.

The function is called in by another script and used to work without issue, the problem is that recently the script is not waiting for the user to input the password it and immediately the calling script is giving an error that null password is provided.

Can someone please help?
The reason must be that a "\n" or ENTER key is still in the stdin buffer by the time that it gets to $password = <STDIN>; which then it gets removed by chomp($password); returning null
# 3  
Old 06-03-2014
Thanks for your reply.

I don't understand how the script know that password in entered in the first place.

as of now the script doesn't wait for password or anything, it just immediately give the error without allowing user to enter any character.

Please advise.
# 4  
Old 06-03-2014
Quote:
Originally Posted by belalr
Thanks for your reply.

I don't understand how the script know that password in entered in the first place.
[...]
Look what happens depending of how the script is called and what's in the STDIN

This is your subroutine in its own script, with minor modifications to display

Code:
#!/usr/bin/perl

# script: pass.pl

use strict;
use warnings;

sub prompt_for_password
{
  my $account_name = $_[0];
  my $account_description = $_[1];
  my $display_prompt = $_[2];

  if ($display_prompt)
  {
    print STDERR "\n";
    print STDERR "Please enter password for $account_description \'$account_name\': ";
  }

  my $LINUX = -d "/initrd";
  my $SOLARIS = -d "/kernel";

  if ($LINUX)
  {
    system "/bin/stty cbreak -echo </dev/tty >/dev/tty 2>&1";
  }

  if ($SOLARIS)
  {
    system "/bin/stty icanon -echo </dev/tty >/dev/tty 2>&1";
  }

  my $password = <STDIN>;

  if ($LINUX)
  {
    system "/bin/stty cbreak echo </dev/tty >/dev/tty 2>&1";
  }

  if ($SOLARIS)
  {
    system "/bin/stty icanon echo </dev/tty >/dev/tty 2>&1";
  }

  if ($display_prompt)
  {
    print STDERR "\n";
  }

  chomp($password);

  return $password;
}


my $pass = prompt_for_password("My First Account", "no description", "What prompt");
print ">>>$pass<<<\n";

my $pass = prompt_for_password("My Second Account", "no description", "What prompt");
print ">>>$pass<<<\n";

Code:
chmod +x pass.pl

call it normally first and observe the output

Code:
./pass.pl

call it now with something in STDIN
Code:
echo -e "screw the user\n" | ./pass.pl

call it now with the equivalent of ENTER in the STDIN
Code:
echo -e "\n" | ./pass.pl

Last edited by Aia; 06-03-2014 at 01:49 PM.. Reason: Adding some clarifications
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