RE: Writing the contents of an array to a file

context has bitten me before.

it's been suggested that to avoid context problems, use something like this:

my $text = join(' ', @file2);
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then print $text to the file.

i had a similar problem yesterday with a textarea in a CGI script i was writing yesterday. the join fixed it.

UPDATE: the scoping is also a problem. i just looked again. @file2 should be declared outside of the block. try a use vars qw/ @file2 / or declare @file2 outside of the while loop.

UPDATE 2: OK - the scoping was the issue, and join is a bit of overkill. :)

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RE: RE: Writing the contents of an array to a file by chromatic (Archbishop) on Sep 28, 2000 at 23:47 UTC
print invokes list context: `[firewheel ~]$ perl my @list = (1 .. 4); print STDOUT @list;` [download] I prefer something like `print STDOUT "@list";`, which is semantically equivalent to `print STDOUT (join($", @array));` Fastolfe is correct, though. This is a scoping issue.	[reply] [d/l] [select]
RE: RE: RE: Writing the contents of an array to a file by Fastolfe (Vicar) on Sep 28, 2000 at 23:49 UTC
FYI, `$"` is to `print "@list"` as `$,` is to `print @list` or `print $a, $b, $c` `@a = qw{ one two }; @b = qw{ tre for }; { local $" = "-"; print "@a @b"; # one-two tre-for } { local $, = "-"; print @a, @b; # one-two-tre-for local $" = ":"; print "@a", "@b"; # one:two-tre:for }` [download] Cheers	[reply] [d/l] [select]
(tye)RE: Writing the contents of an array to a file by tye (Sage) on Sep 29, 2000 at 00:06 UTC
Note also that while each pair of lines of code below produce the same output: `print FILE "@array"; print FILE join $", @array; print FILE @array; print FILE join $,, @array;` [download] they are not equivalent in terms of performance. Only `print FILE @array` avoids building a potentially huge string in memory before writing. In practice, the speed improvement is usually small (or even negative) but I prefer to allow for huge arrays and avoid the `join` if I'm just going to write the result to a file and then throw the constructed string away. Though I do find appealing the way that using `join` prevents your code from breaking if you accidentally sneak a scalar context into the mix (typing a "." when you meant a ",", for example). - tye (but my friends call me "Tye")	[reply] [d/l] [select]
RE: RE: Writing the contents of an array to a file by Fastolfe (Vicar) on Sep 28, 2000 at 23:46 UTC
In this case, a join is unnecessary (but still perhaps valuable for others that need to do similar acts in the future): `@a = (1, 2, 3); print @a; print $a[0], $a[1], $a[2]; # equivalent to @a` [download] Passing arguments to a function (even internal) as an array is just like passing a list of your own individual arguments. In this case, however, each element will be printed one after another. If you want to separate with spaces, either set `$,` or use join as you've done. If you're working from a list generated from a file, though, as we are here, newlines are still at the end of each element in the list, so printing them out like he's doing will have the desired effect: `@list = <INPUT_FILE>; print OUTPUT_FILE @list; # exact (textual) copy` [download]	[reply] [d/l] [select]