CODEWITHSUNDEEP
perl
Eugen Konkov
Eugen Konkov

Reputation: 25133

Argument isn't numeric in bitwise or (|) at. Why?

I am using code from here:

#!/usr/bin/perl

use strict;
use warnings;

use Fcntl;
my $flags =  "";
fcntl( STDIN, F_GETFL, $flags) || die $!;
$flags |= O_NONBLOCK;
fcntl( STDIN, F_SETFL, $flags) || die $!;

But get next error:

Argument "\0O§"­U\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0..." isn't numeric in bitwise or (|) at /home/user/inetd-script.pl line 9.

$flags is initialized by fcntl call. Tell me please why this error occur.

And how to fix it.

UPD
Perl cookbook 7.20.2 initialized it as empty string.

enter image description here

Upvotes: 0

Views: 698

Answers (1)

ysth
ysth

Reputation: 98388

The bitwise operators have two flavors, string and numeric. If either operand is numeric, or the "bitwise" feature[^1] is enabled, it is treated as a numeric bitwise. In that case, if an other operand is a string, it is converted to a number, and a warning is generated if it doesn't look like a number.

You should be initializing $flags to 0, not "".

[^1]: the "bitwise" feature makes the normal bitwise operators only do numeric bitwise, and adds new string bitwise operators such as |..

Upvotes: 6

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