Perl - use 0 if string is empty

Question

When using arithmetic expressions in combination with an undefined or empty string, perl throws an error. Is there a clean way to use zero in case a string is empty?

This does not work:

$x = 1 + $emptyVar

In bash you could use something like this for instance to use zero if the variable $emptyVar is empty:

x=1+${emptyVar:-0}

I am looking for something similar as this

Tanktalus · Accepted Answer · 2016-11-23 00:06:01Z

5

There are many ways to do this. e.g.:

$x = $emptyVar;
$x += 1;

or maybe:

$x = 1 + ($emptyVar // 0); # defined-or operator

or maybe:

{
  no warnings 'uninitialized';
  $x = 1 + $emptyVar;
}

Of these, I usually use the second one. If the level of perl I'm using doesn't have defined-or, then a simple or (||) works fine, too.

answered Nov 23, 2016 at 0:06

Tanktalus

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5 Comments

Subbeh Over a year ago

Thanks! Exactly what I was looking for

ysth Over a year ago

the question says undefined or empty string, so $x = 1 + ($emptyVar || 0); instead

Tanktalus Over a year ago

@ysth - true, though when likening to shell where "empty" and "undef" are largely indistinguishable, I figured there was a good chance that's what OP meant.

Borodin Over a year ago

++($x = $emptyVar)

tomi Over a year ago

I find the defined-or useful in case like: exit 0 if (fork // -1) -- otherwise I cannot distinguish between fork failing (unlikely but possible) and child process. tried with strace -f -e trace=process perl -le 'print "foo" if (fork // -1)' to see this may be useful...

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