Re^2: quoted execution not working

my $pid=fork(); if ( $pid == 0 } { : child process goes here } elsif { $pid > 0 ) { : parent process wait(); # Wait for the child to exit } else { # WOAH! We should never get here! die "fork returned $pid"; }
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There are two things wrong with that. If the fork fails, $pid is undef, but will still compare true to 0. Second, if it fails, the error is in $!, not $pid. So you actually want:

my $pid=fork();
if (not defined $pid) {
    die "fork failed: $!\n";
}
elsif ( $pid == 0 } {
   : child process goes here
}
else {
   : parent process
    wait();  # Wait for the child to exit
}
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Dave.

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Re^3: quoted execution not working by blue_cowdawg (Monsignor) on Jul 28, 2004 at 00:10 UTC
If the fork fails, $pid is undef, but will still compare true to 0. Second, if it fails, the error is in $!, not $pid. Good catch! You are correct. My bad. Instead of `die "fork returned $pid";` [download] I should have invoked `die $!;` [download] as I have in code that I have written in the past where I have done forking. Too much C-code lately the if-tree is a C-ism. As in `pid = fork(); switch (pid){ -1: perror("Fork failed"); exit(-1); 0: /* Child / break; default: / parent */ break; }` [download] anyway, good catch. All all this code is off the top of my head.	[reply] [d/l] [select]

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Re^3: quoted execution not working
by blue_cowdawg (Monsignor) on Jul 28, 2004 at 00:10 UTC

If the fork fails, $pid is undef, but will still compare true to 0. Second, if it fails, the error is in $!, not $pid.

Good catch! You are correct. My bad. Instead of

die "fork returned $pid";
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die $!;
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pid = fork();
switch (pid){
-1: perror("Fork failed");
    exit(-1);
0: /* Child */
   break;
default:
    /* parent */
   break;
}
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All all this code is off the top of my head.

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