Perl string comparisons

Xris718 · 04-01-2005, 10:31 AM

Hi

I need to know how to do string comparisons in perl just like shell does. How do you convert the following into perl?
ie:

if [-n "$string"]; then
statement.....

if [-z "$string"]; then
statement...

if [$var -gt 0]; then
statement...

david_ross · 04-01-2005, 11:20 AM

I think this is what you want:

Code:

if($string){
 print "Variable exists\n";
}
if(!$string){
 print "Variable is empty\n";
}
if($string>0){
 print "Variable greater than 0\n";
}

Xris718 · 04-01-2005, 12:42 PM

thank you i think thats it!

Xris718 · 04-01-2005, 01:06 PM

oh what about this convert into perl?
ie:

if [! -z $string]; then
something....

puffinman · 04-01-2005, 02:42 PM

You might be interested in the "defined" function.

Code:

if($string) {
    # string exists and evaluates as true
} elsif(defined $string) {
    # string exists but evaluates as false
} else {
    # string doesn't exist
}

Also, you can use numerical comparisons directly on strings, if they consist of just a number Perl will treat them as a number. On the other hand, you can use the "eq" operator to test equality as a string. (All the numerical comparison operators have string versions)

Code:

$number = 2;
$number_string = "02";

if ($number == $number_string) {
    print "Variables are numerically equal.\n";
}
if ($number eq $number_string) {
    print "Variables are equivalent strings.\n";
}

Run this and you'll see that the first statement is printed but not the second.

MetaPhase · 04-03-2005, 10:43 AM

Quote:

Originally posted by Xris718
oh what about this convert into perl?
ie:

if [! -z $string]; then
something....

How is the test:

Code:

[! -z $string]

different from the test

Code:

 [-n $string]

?