Re: Beginner in perl : Use of uninitialized value

Just another tip: there is no need to read all of STDIN into an array; you can iterate over each line as it comes in.

while ( my $line = <STDIN> ) {
    ...
}
[download]

The diamond operator <> will do some pretty fancy stuff for you by default. You can for example leave out the explicit STDIN:

while ( my $line = <> ) {
    ...
}
[download]

What is really cool about this is that now in addition to working with STDIN you can also pass a list of filenames to your Perl program and it will do the right thing.

See perlop - IO Operators for more details on the diamond operator.

Of course you also don't need to set an explicit loop variable for a program of this size; you can just use $_:

while (<>) {
    ...
}
[download]

And at this point, you may want to look into Perl's -n command line option, which will automatically wrap your entire program inside that exact same loop:

bash:~$ perl -nE '...'
[download]

πάντων χρημάτων μέτρον έστιν άνθρωπος.

Comment on Re: Beginner in perl : Use of uninitialized value Select or Download Code

Replies are listed 'Best First'.
Re^2: Beginner in perl : Use of uninitialized value by jwkrahn (Abbot) on Dec 28, 2018 at 19:41 UTC
Just another tip: there is no need to read all of STDIN into an array; you can iterate over each line as it comes in. `foreach my $line (<STDIN>) { ... }` [download] The problem with that is that the foreach loop will read all lines into a list in memory first. You need a while loop to iterate over one line at a time: `while ( my $line = <STDIN> ) { ... }` [download]	[reply] [d/l] [select]
Re^3: Beginner in perl : Use of uninitialized value by jimpudar (Pilgrim) on Dec 28, 2018 at 20:20 UTC
Quite right, that's what I get for posting without testing my code :). I edited my comment to correct this. πάντων χρημάτων μέτρον έστιν άνθρωπος.	[reply]
Re^4: Beginner in perl : Use of uninitialized value by Perl_Programmer1992 (Sexton) on Dec 29, 2018 at 07:42 UTC
Thank you @jwkrahn and @jimpudar , it's been such a great learning so far , I will definitely keep these things in mind when coding next time.	[reply]