On 2011-11-05 14:49, Ken Peng wrote:
δΊ 2011-11-5 21:03, Shawn H Corey ει:
You're assuming that perl clears $! at the start of your script. Never
assume a variable has a valid value unless you set it yourself. In other
words, always initialize your variables.
It did clear it, see this:
$ perl -le 'print $!;open HD,"/etc/passwd" or die;<HD>;print $!'
Bad file descriptor
I don't know where the $! get setted.
Who cares? You should only use $! *immediately* after an error.
Like with eval, don't gamble on values of global variables,
but use the return value of the 'open'.
How *not* to do it:
perl -Mstrict -wle'
{ local $!;
print "1:", $!;
open my $fh, "/etc/passwd" or die "ERROR: $!";
print "2:", $!;
<$fh>;
print "3:", $!;
}
print "4:", $!;
'
1:
2:Inappropriate ioctl for device
3:Inappropriate ioctl for device
4:
These 2 and 3 are irrelevant intermediate issues at the system level, so
just don't go there.
--
Ruud
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