Hello fellow Monks! I'm trying to write a daemon that runs a curl command. 
use IO::Socket;
use POSIX qw(WNOHANG setsid);

sub daemonize {
        $SIG{CHLD} = 'IGNORE';        # Configure to autoreap zombies
        die "Can't fork" unless defined ( my $child = fork );  # FORK 
+<<<<<<<<<<<<
        CORE::exit(0) if $child;      # Parent exits
        setsid();                     # Become session leader
        open( STDIN,  "</dev/null" ); # Detach STDIN from shell
        open( STDOUT, ">/dev/null" ); # Detach STDOUT from shell
        open( STDERR, ">&STDOUT"   ); # Detach STDERR from shell
        chdir '/tmp';                 # Change working directory
        umask(0);                     # Reset umask
        $ENV{PATH} = '/bin:/sbin:/usr/sbin';  # Reset PATH
        }

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Looks like my script is hanging when I daemonize it. I'm logging to a CSV file, and I finally added some code in tracing this back to where it is hanging, and it looks like it's when I shell out.

sub cmd_wrapper { 
    my $cmd = shift;
    my @out; 
    eval { 
        local $SIG{ALRM} = sub { die "alarm\n" };
        alarm 15;
## (CSV output logged) ##
        @out = qx[$cmd];  #<<<<< Shell out
## (CSV output *NOT* logged) ##
        alarm 0;
        };
    return $@ if $@ ne "" 
    return wantarray ? @out  : join '', @out;
    }

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What's even stranger is if I uncomment my $? == -1 check in the subroutine that calls cmd_wrapper I see log entries indicating it failed (though I appear to be getting valid results back; guessing $? doesn't work well when forking). But I'm at loss to explain how code appearing after I shell out affects the shelling out behavior. 
    ## Run the Curl command ##
    my $restURL = $opt_ref->{restURL} . $opt_ref->{pagingURL};
    say "DEBUG: \$restURL: \]$restURL\[" if $cfg{debug} or $cfg{test};

    my $cmd = "$curlCommand -X $opt_ref->{method} $restURL";
    my $results = cmd_wrapper( $cmd, $opt_ref, $info_ref, $cfh{csv_exp
+ort}, \@rpt_hdr, 1 );
    say 'DEBUG: $results: ', Dumper $results if $cfg{debug}; #or $cfg{
+test} > 1;

    $info_ref->{name} = $?;
    $info_ref->{primary} = $cmd;
    $info_ref->{status_msg} = $results;

#=pod
# Uncommented I see results, Commented out cmd_wrapper seems to hang.
    ## CASE: Connection issue
    if( $? == -1 ) {   # WARN:  Will this still work now that I'm call
+ing cmd_wrapper()???
        $info_ref->{entry_level} = 'DEBUG';
        $info_ref->{status} = 'runCurl connection failed';
        csv_log( $opt_ref, $info_ref, $cfh{csv_export}, \@rpt_hdr, 1 )
+;                    
        return;  #<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< 
+RETURN
        }
#=cut

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Am I missing something simple? Something with buffering? Or hitting an optimization problem? Something to do with that return? Or....? 

This is perl 5, version 16, subversion 3 (v5.16.3) built for x86_64-li
+nux
Red Hat Enterprise Linux Server release 5.11 (Tikanga)

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In reply to Forking and shelling out to curl by Argel

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