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How to Limit <STDIN> User-Input Entry?

mar85
Novice

Mar 21, 2013, 6:20 PM

Post #1 of 3 (83 views)

How to Limit <STDIN> User-Input Entry?	Can't Post

Hello,
I've recently practicing to write perl scripts and am trying to write a code to get 5 input entries from the user and store the entries to an array. However, when executed, it seems that it endlessly asking for the user-input, and not 5 times. Below is the code:

Code

my @user_input = (); 
my $i = 0; 
 
#foreach (<STDIN>) 
for(my $i=0; $i<5; $i++) 
{ 
        chomp; 
        print "Enter entry no.$i: \n";   
        push @user_input, <STDIN>;  
} 
 
print "@user_input\n";

Is there any mistake in the code?
Thanks

BillKSmith
Veteran

Mar 21, 2013, 8:05 PM

Post #2 of 3 (76 views)

Re: [mar85] How to Limit <STDIN> User-Input Entry? [In reply to]	Can't Post

Code

       push @user_input, scalar <STDIN>;

The second of argument of push is a LIST. (Refer perldoc -f push) This imposes list context on <STDIN>. In list context, the diamond operator (<>) reads an entire file.

Your code actually works as you expect if you manually enter an end-of-file character after every input record.
(Under windows, enter one datum, RETURN, and CTRL-Z)

As a matter of style, always use strict and warnings. Seldom (if ever) use the C-style for loop. In this case, I think it is clearer to use a scalar variable to impose scalar context on <>. Use <> rather than the explicit <STDIN> unless you know the difference. Even better, use a prompt module from CPAN.

The following code does not chomp the input becuse the returns are neded in the output.

Code

use strict; 
use warnings; 
my @user_input; 
for  my $i (1..5) { 
    print "Enter entry no.$i: \n"; 
    my $datum = <>; 
    push @user_input, $datum; 
} 
print @user_input, "\n";

Good Luck,
Bill

(This post was edited by BillKSmith on Mar 21, 2013, 8:06 PM)

mar85
Novice

Mar 22, 2013, 12:03 AM

Post #3 of 3 (73 views)

Re: [BillKSmith] How to Limit <STDIN> User-Input Entry? [In reply to]	Can't Post

Thank you Bill for the explanantion. Really helps

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