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steelcityamir
steelcityamir

Reputation: 1218

Perl map function output assigned to variable

I'd like to concatenate the output of the map function in Perl to a string variable. However, if I try this:

$body .= map {"$_\n"} sort(@{$hash{$server}->{VALID}});

The value of $body equals 3 instead of the expected

user1
user2
user3

If I do: 

print map {"$_\n"} sort(@{$hash{$server}->{VALID}});

it gives me what I want.

So how can I mimic the print map functionality and assign it to the body variable?

Upvotes: 1

Views: 849

Answers (2)

creaktive
creaktive

Reputation: 5220

print concatenates the array returned by map, interleaving items with the value of $,. So, you need this to simulate print behavior:

$body .= join $,, map {"$_\n"} sort(@{$hash{$server}->{VALID}});

As long as print is your concern, another valid possibility is:

print "$_\n" for sort(@{$hash{$server}->{VALID}});

Or, enabling Perl v5.10 feature say, just:

say for sort(@{$hash{$server}->{VALID}});

Extrapolating that for concatenation:

$body .= "$_\n" for sort(@{$hash{$server}->{VALID}});

Upvotes: 4

friedo
friedo

Reputation: 66998

map is used to transform a list into another list, so that's what it returns. This works with print because the print function takes a list and will output them separated by the value of $, (the output field separator.)

If you want to join a list together into a string, you have to use join.

$body .= join "\n", sort(@{$hash{$server}->{VALID}});

Upvotes: 5

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