Maybe someone can explain || vs or

[travs69]

I always thought they were interchangeable till today.

	my @trapd_file_list = qx{$remsh $trapd_log_server $ls $trapd_log_path/$trapd_server} || &senderror("$remsh $trapd_log_server $ls $trapd_log_path/$trapd_server : $!", 'exit');
	print "$#trapd_file_list\n";
	my @trapd_file_list = qx{$remsh $trapd_log_server $ls $trapd_log_path/$trapd_server} or &senderror("$remsh $trapd_log_server $ls $trapd_log_path/$trapd_server : $!", 'exit');
	print "$#trapd_file_list\n";
	my @trapd_file_list = qx{$remsh $trapd_log_server $ls $trapd_log_path/$trapd_server};
	print "$#trapd_file_list\n";

which prints
0
744
744

I found very little explaining || vs or, I can't get to perldoc or cpan right now.. and only found a small tidbit about || binding more tightly on google, but didn't really have a good explanation.

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Travis - Those who say it cannot be done are usually interrupted by someone else doing it; Give the wrong symptoms, get the wrong solutions;

 

[Kirsle]

http://linux.die.net/man/1/perlop

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[rvBasic]

C-Style logical operators (|| , &&) will evaluate to 0 or 1. Perl's operators return the last value evaluated. This can be used to your advantage in an expression like
$a=$b||$c||$d;
which will assign to $a the value of the first scalar that is true (=different from zero)

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In theory, there is no difference between theory and practice. In practice, there is. [attributed to Yogi Berra]

 

[KevinADC]

general rule of thumb, stick to "or" for flow control, use || for assignment. "or" has the lowest precedence of all perl operators.


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- Kevin, perl coder unexceptional!

 

[ishnid]

C-Style logical operators (|| , &&) will evaluate to 0 or 1. Perl's operators return the last value evaluated.

That's not the case. From perlop:

The "||" and "&&" operators return the last value evaluated (unlike C's "||" and "&&", which return 0 or 1).

The difference between || and or is their precedence.

 

[rvBasic]

ishnid You're absolutely right: I wrongly added these symbols to the C-style operators. Leave them out and the eample is fine.

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In theory, there is no difference between theory and practice. In practice, there is. [attributed to Yogi Berra]