Beefy Boxes and Bandwidth Generously Provided by pair Networks
There's more than one way to do things

Re: slurping __DATA__

by jeffa (Bishop)
on Aug 08, 2003 at 14:17 UTC ( #282187=note: print w/ replies, xml ) Need Help??

in reply to slurping __DATA__

do is "not really a function". It is a block that has a seperate scope from wherever it was called from. This allows you to localize $/ so that when execution leaves our "temporary" scope, $/ will be what it was before it was changed.

If you look up $/ in perlvar, you will see

   You may set it to a multi-character
   string to match a multi-character terminator, or
   to "undef" to read through the end of file.
Finally, <DATA> returns the next line from the filehandle DATA, and since $/ is undefined, the entire contents of the file are returned and "caught" in a scalar.

UPDATE: i should add that this is one of those few cases where local is a good choice. For example,
local $/;
Is essentially the same as
local $/ = undef;
Which is not the same as
$/ = undef;
Even though that last snippet will be contained inside a do block ... $/ will still be undef afterwards. Try this - make two files foo.txt and bar.txt and run this:
# print entire file open FH,'foo.txt'; my $foo = do {$/ = undef;<FH>}; print $foo; # print only first line open FH,'bar.txt'; my $bar = <FH>; print $bar;
Then go back and add local to the do block.


(the triplet paradiddle with high-hat)

Comment on Re: slurping __DATA__
Select or Download Code
Replies are listed 'Best First'.
Re: Re: slurping __DATA__
by LanceDeeply (Chaplain) on Aug 08, 2003 at 14:44 UTC

    I did read perldoc perlvar but I didnt know that local $/; was undef-ing it for the do's block context. I'll have to go brush up on local, 'cause I never use it.

Log In?

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://282187]
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others examining the Monastery: (10)
As of 2015-11-25 14:50 GMT
Find Nodes?
    Voting Booth?

    What would be the most significant thing to happen if a rope (or wire) tied the Earth and the Moon together?

    Results (679 votes), past polls