On Tue, 19 Jun 2001 03:09:54 +0200 (MEST), Louis Pouzin wrote:
>I want to test and remove one element of an array when it is '-s'.
>
>The following script works, with a diag: Use of uninitialized value, in line 5. It
>seems related to '-s'.
>
> #!/usr/local/bin/perl -w
> @ARGV = (2, '-s', 'fil');
> my $sel = 0;
> for (0..$#ARGV) {
> $ARGV[$_] =~ /^-s$/o || next;
> $sel = 1; splice(@ARGV,$_,1);
> }
> print "$sel, @ARGV \n";
> __END__
>
>If I replace -s by -\s or -\\s, the diag disappears, but the regex fails. What is a
>right way to do it ?
The reason is that, when you do that, your @ARGV gets smaller. So you're
testing beyond the end of the array. Plus: you're skipping a file.
You're testing items 0, 1 and 2, but if 1 is dropped, then 2 becomes 1,
and you don't test it.
Some solutions:
* Do it with a C style for loop (or a while loop), and increment only
if there was no splice.
for(my $i = 0; $i < @ARGV; ) {
if($ARGV[$i] eq '-s') {
splice @ARGV, $i, 1;
} else {
$i++;
}
}
Very messy, if you ask me.
* Go backwards through the array.
for(reverse 0 .. $#ARGV) {
if($ARGV[$_] eq '-s') {
splice @ARGV, $_, 1;
}
}
Better.
* But my favourite is to use grep():
@ARGV = grep { $_ ne '-s' } @ARGV;
Caveat: all untested. How unresponsible. And you have to put the test
for whether '-s' was there, in it somewhere.
--
Bart.
