autosplit behaviour with and without F

Jasper has asked for the wisdom of the Perl Monks concerning the following question:

I was puzzled when my script gave me different behaviour when I attached an F to the switches:

[jmccrea@juno jmccrea]$ cat testy2

#!perl -ap
split;

[jmccrea@juno jmccrea]$ perl -MO=Deparse testy2

LINE: while (defined($_ = <ARGV>)) {
    @F = split(/\s+/, $_, 0);
    split(/\s+/, $_, 0);
}
continue {
    print $_;
}
testy2 syntax OK

[jmccrea@juno jmccrea]$ cat testy 

#!perl -apF
split;

[jmccrea@juno jmccrea]$ perl -MO=Deparse testy 

LINE: while (defined($_ = <ARGV>)) {
    @F = split(/\n/, $_, 0);
    split(/\s+/, $_, 0);
}
continue {
    print $_;
}
testy syntax OK
[download]

So with the F, the autosplit splits on /\n/, otherwise on /\s+/. Having thought about it, it appears that the next character after the F is interpreted as the pattern on which to split, that character being a carriage return. It just seems very odd that it wouldn't grab the empty string instead. Can't find anything in the docs.

Jasper

Comment on autosplit behaviour with and without F Download Code

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Re: autosplit behaviour with and without F by Abigail-II (Bishop) on Aug 13, 2003 at 13:19 UTC
I cannot duplicate that. `$ cat -vET ttt #!/usr/bin/perl -apF$ split;$ $ perl -le 'print $]' 5.008 $ perl -MO=Deparse ttt LINE: while (defined($_ = <ARGV>)) { our(@F) = split(" ", $_, 0); split(" ", $_, 0); } continue { print $_; } ttt syntax OK $` [download] Note that also the first argument of split is translated differently (and incorrect in your case). Perhaps you are dealing with an older version of Perl, which has even more bugs in `B::Deparse`? Abigail	[reply] [d/l]
Re: Re: autosplit behaviour with and without F by Jasper (Chaplain) on Aug 13, 2003 at 13:30 UTC
I'm using 5.6.0, so you're probably right. It's not Deparse, though, the program runs differently (in the way Deparse indicates), so it's Perl that's at fault. I can't duplicate it in 5.8.0, either, so it would appear to be 'fixed'. Jasper	[reply]
Re3: autosplit behaviour with and without F by dragonchild (Archbishop) on Aug 13, 2003 at 13:44 UTC
If you can't duplicate it 5.6.1, I would call it one of the many bugs in 5.6.0. ------ We are the carpenters and bricklayers of the Information Age. The idea is a little like C++ templates, except not quite so brain-meltingly complicated. -- TheDamian, Exegesis 6 Please remember that I'm crufty and crochety. All opinions are purely mine and all code is untested, unless otherwise specified.	[reply]
Re: autosplit behaviour with and without F by tbone1 (Monsignor) on Aug 13, 2003 at 13:19 UTC
It may be ... may be ... that the \n is the default for the -F switch if no pattern is given. I am at work, so I can't go delving into source code to look at this, but now you've piqued my curiosity. -- tbone1 Ain't enough 'O's in 'stoopid' to describe that guy. - Dave "the King" Wilson	[reply]
Re: autosplit behaviour with and without F by jsprat (Curate) on Aug 13, 2003 at 15:19 UTC
I get the same thing on a 5.6.0 installation, but not on 5.8. Changing the shebang from `#!perl -apF` to `#!perl -aF -p` fixes it.	[reply] [d/l] [select]
Re: Re: autosplit behaviour with and without F by Jasper (Chaplain) on Aug 15, 2003 at 12:10 UTC
Changing the shebang from #!perl -apF to #!perl -aF -p fixes it. Not for me, it doesn't. Deparse reads the -aF -p thing as: `split(/\s+/, $_, 0);` So it ignores the -p bit totally. That's not so good. -p -aF, on the other hand, seems fine. Jasper	[reply] [d/l]
Re: autosplit behaviour with and without F by bsb (Priest) on Aug 28, 2003 at 09:40 UTC
I think there's a bug when the -F is last. I've noticed this before when scripts that worked under linux broke under windows. The -F argument contained "\r" which broke the BEGIN block that the -F produces (toke.c:2457) So don't put -F last. `echo "a:b" \|perl "-lanF:\r" -e 'print $F[1]' $ echo "hi=there" \| perl '-lanF/=/);print("JAPH"' -e 'print @F' JAPH hithere perl "-lanFi'~#" -e1 perl $'-lanFi\'~#\200' -e1` [download]	[reply] [d/l]