UNIX for Dummies Questions & Answers

Hi friends,

I am not sure if perl questions can be raised here.
But I have a doubt if there is a way to do "#define" in perl, like in C.

Does anyone know if it is feasible (without CPAN modules)?

Thanks,
Srini

Please understand that #define is a preprocessor directive. Strictly, it is not related to C.

If all you want is named constants, you can try the constant pragma:

constant - perldoc.perl.org

Hi,
Thanks for your quick suggestion. I grazed over the 'constant' pragma.
From the given link,

Code:

 it's probably not correct to put a constant declaration inside of a conditional statement

My main aim is to use the constant in a 'if' condition.
To elaborate, my scenario is:

Code:

if(defined($input_file)) {
  open(FH,"<$input_file);
  #define INPUT "FH";
} else {
  #define INPUT "STDIN";
}
while ($line = <INPUT>) {
...
}

Is there an apposite mechanism to replace that "#define"?

Thanks,
Srini

check if Constant::Runtime module is useful in your case

Then that is not strictly a "constant".

Why do you have to do it like that? You can take a reference of a filehandle and then use it with the slurp ( <> ).

Code:

if(defined($input_file)) {
  open(FH,"<$input_file);
  $input = \*FH;
} else {
  $input = \*STDIN;
}
while ($line = <$input>) {
...
}

@YOGESH => Thanx for the suggestion. But since I don't have permissions to use CPAN modules, I am not able to try it out as well.
@CBKIHONG => Your solution works perfectly. Thanks a lot!
Also, please enlighten me if "\*" is used to get the address of a symbol and "\$" to get the address of a variable.

Since I'm a beginner in perl, my queries might sound frivolous.

Thanks,
Srini

Mostly, yes, although the whole truth is more complicated. Look it up from the camel books when you have reached that far.