Gary Stainburn <[EMAIL PROTECTED]> wrote:
> unlink $file if -e $file;
>
> if (-e $file) {
> for($i = 0; $i < 10; $i++) {
> sleep(1);
> }
> unlink $file;
> }
>
> The if statement controls access to the block following it. The
> condition is only checked once, so the answer to the first part
> is yes - if another program deletes the file within the 10 seconds
> your script will try to delete a non-existant file.
>
> unlink $file if -e $file;
>
> This will do what you want, and if another prog does delete the file
> in during the sleep the unlink won't be called.
But it *will* try to delete a nonexistant file if the other process
comes along between the "if -e $file" and the "unlink $file".
Since there's not any error checking (and since calling unlink()
twice probably isn't cause for alarm) you won't even notice the
race condition.
But it's still wrong. :)
use Errno;
unlink $file or $!{ENOENT}
or warn "Couldn't unlink '$file': $!";
Here there's no race, and a sensible message if you're going to
leave the file sitting there.
--
Steve
perldoc -qa.j | perl -lpe '($_)=m("(.*)")'
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