As an alternative, say print ... if $ARGV eq '-', then you'll only be prompting if you're actually reading from STDIN. The output-only results printing can be unconditional.

-- Randal L. Schwartz, Perl hacker

Sir,
It seems like this may be a very desireable action at times. EG. in the case where you want a script to be interactive, but also have it cronned with all of the values for it in another file. In which case <> will do exactly what you want in both cases. Isn't this more a question of style that what SHOULD/SHOULDN'T be done?

-Fatty Lumpkin

Update: Merlyn is 1000% correct, poor reading on my part, i missed the actual printed prompt.I am just used to doing something like


shift || (print "\nprompt:" and <>);
[download]


But that doesn't allow for this behavior either.I missed the point, Thanks for correcting me.

It seems like this may be a very desireable action at times. EG. in the case where you want a script to be interactive, but also have it cronned with all of the values for it in another file. In which case <> will do exactly what you want in both cases.

In which case, you don't want to prompt, because then you get a bunch of prompts in the output, without responses. That... looks... tacky. I'd fatal that in a code review.

-- Randal L. Schwartz, Perl hacker

It works then but allows letters... maybe wrap it in an int()?

Update Wrapping it in an int makes letter entries zero, maybe instead of chomp do

#!/prod/gnu/bin/perl

print "** Random 4 Lotto Numbers **\n";
print "** Type any four digits (0 to 9) **\n\n";

for ($i=1; $i <= 4; $i++) {
    print "Choice $i: ";
    ($digit[$i] = <>) =~ s/\D//g;
    redo unless $digit[$i];
    redo if $digit[$i] > 9;
    redo if $digit[$i] < 0;
}

print "Your choices :@digit \n";
[download]

Thanks suaveant for spotting the typo. The example came in the cd but i didn't spot that.

And if you're going to test the input with a regular expression, then use that on the redo line:

print "** Random 4 Lotto Numbers **\n";
print "** Type any four digits (0 to 9) **\n";

for ($i=1; $i <= 4; $i++) {
     print "Choice $i: ";
     chomp ($digit[$i] = <STDIN>);
     redo if $digit[$i] !~ /^\d$/;
 }
 
 print "Your choices :@digit \n";
[download]

iakobski

redo if $digit[$i] !~ /^\d$/;
[download]

Or the much simpler:

redo if $digit[$i] =~ /\D/
[download]

-- Randal L. Schwartz, Perl hacker

yours is good, but why chomp? no need with that regexp...

print "** Random 4 Lotto Numbers **\n";
print "** Type any four digits (0 to 9) **\n";

for ($i=1; $i <= 4; $i++) {
     print "Choice $i: ";
     redo if ($digit[$i] = <STDIN>) !~ /^\d$/;
}
   
print "Your choices :@digit \n";
[download]

since the $ works fine with \n there
                - Ant

use strict;
print "** Random 4 Lotto Numbers **\n";
print "** Type any four digits (0 to 9) **\n";

my @digit;
foreach my $i (1..4){
while ($digit[$i] =~/^[\D]$/){
    print "enter digit $i : ";
    chomp($digit[$i] =<>)};
}
print "Your choices  : @digit \n";
[download]

It is good to point out that use strict is needed here.

If you also add use warnings, you will notice that the print statement is accessing an undefined value,  $digit[0] I suspect that the original author meant to say the equivalent of

foreach my $i ( 0..3){
[download]

or if not the print should be:

print "Your choices  : @digit[1..4] \n";
[download]

iakobski

From Programming Perl, 3rd Edition Page 118

     The foreach keyword is just a synonym for the for keyword, so you
+ can use foreach and for interchangeably...
[download]


                - Ant

well, YES, that is true.
however, from perl's documentation on continue :

If there is a continue BLOCK attached to a BLOCK (typically in a while or foreach)...


which made me believe you could tack continues on to any block all willy nilly. This isn't the case, though.