«

Hi,

I m not sure whether the following Perl code is correct with fork().

while (1) {
if (open( FILE, "< $books" ) {
if (!defined($kidpid = fork())) {
die "cannot fork: $!";
}
elsif ($kidpid == 0) { # child
child_func();
}
else # parent.
sleep(1);
}
}

Can anyone please give comment and suggestion of improving it?

Thanks
Sam

bsder <> wrote:

> I m not sure whether the following Perl code is correct with fork().
>
> while (1) {
> if (open( FILE, "< $books" ) {
> if (!defined($kidpid = fork())) {
> die "cannot fork: $!";
> }


Control can never get here if the fork() failed, so...


> elsif ($kidpid == 0) { # child


.... you don't need an elsif, just an if would do.


> child_func();
> }


Control can never get here in the child process, so ...


> else # parent.


.... you don't need an else at all.

(and if you did need an else, you would need an opening curly bracket)


> sleep(1);
> }
> }
>
> Can anyone please give comment and suggestion of improving it?


# untested
while (1) {
if (open( FILE, "< $books" ) {
die "cannot fork: $!" unless defined($kidpid = fork());

if ($kidpid == 0) { # child
child_func();
}
# parent
sleep(1);
}
}

--
Tad McClellan SGML consulting
Perl programming
Fort Worth, Texas

bsder <> wrote:
> Hi,
>
> I m not sure whether the following Perl code is correct with fork().
>
> while (1) {
> if (open( FILE, "< $books" ) {

Syntax error, unbalanced parens. Also, you wouldn't you want to do
something more intelligent in case the file can't be opened?


> if (!defined($kidpid = fork())) {
> die "cannot fork: $!";
> }
> elsif ($kidpid == 0) { # child
> child_func();

child_func() had better never return, or else you are making a fork-bomb.

> }
> else # parent.
> sleep(1);
> }
> }
>
> Can anyone please give comment and suggestion of improving it?

Without knowing what it is supposed to do?

Xho

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[A complimentary Cc of this posting was sent to
Tad McClellan
<>], who wrote in article <>:
> # untested

> while (1) {
> if (open( FILE, "< $books" ) {
> die "cannot fork: $!" unless defined($kidpid = fork());
>
> if ($kidpid == 0) { # child
> child_func();
> }
> # parent

How should I guess looking on this code that child_func() never
returns? IMO, one should at least move exit() out of child_func()
into the main loop to make the intent clear...

> sleep(1);
> }
> }

Hope this helps,
Ilya

Jim Gibson wrote:
>
> You should use the 3-argument version of open(). You should print why
> open did not succeed if it failed. It is usually better to use
> variables rather than barewords for file handles:
>
> if ( open( my $file, '<', $books ) ) {
^^^

> ...
> }else{
> die("Can't open $books for writing: $!");
^^^^^^^
I'm not suprised that it won't open for writing.


John
--
use Perl;
program
fulfillment