system function is returning status -1 when running a unix command

[elf_firein]

I am facing a strange problem with perl code. I have a perl package abc.pm which has following subroutine:

sub DB_xxx
   {
    my ($dbUser, $dbPass, $db, $autoCommit) = @_;
    my $dbh;

    # logon to DB
    unless( $dbh = DBI->connect('dbi:Oracle:' . ($$db || ''), $$dbUser
+, $$dbPass,
                                {AutoCommit => $$autoCommit}) )
      {

      croak "Error connecting to database $DBI::errstr \n";

      }
                 
    return $dbh;

   }

This method is for connecting to database

Inside my own .pl file I am using this subroutine in following manner:

use abc qw (DB_xxx);

my $dbh;
my $stat1 = system ("gzip -t xyz.gz");
print "The stat checking:$stat1\n";

my $userid = xxx;
my $passwd = xxx;
my $database = xyz;
my $autocommit = 0;

$dbh=DB_xxx(\$userid, \$passwd, \$database, \$autocommit);

my $stat2 = system ("gzip -t xyz.gz");
print "The stat checking:$stat2\n";

The problem is:the value of $stat1 is 0 but value of $stat2 is -1. though the .gz file is same in same location. In Solaris 8 box but in $stat1 & $stat2 have values 0 for both. But in solaris 10 box giving to two differnt output:$stat1=0 & $stat2=-1

I have also printed $!: For $stat2 it is showing error message: / No child process/

Can anybody please help me? Please it is urgent.

[ikegami]

Sounds like your DB stuff is messing with SIGCHLD.

$ perl -wle'$SIG{CHLD}="IGNORE"; print system("ls -d ."); print $!'
.
-1
No child processes

system is basically fork + exec (in the child) + waitpid (in the parent). In the above example, children are auto-reaped, so system has no child to wait for, so it returns an error.

strace (or truss or whatever it's called on Solaris) would confirm this diagnosis.

Update: Added last line.

[repellent]

ikegami, could you please explain what is going on here:

> perl -wle '
$SIG{CHLD}="IGNORE";
$! = 33;
print system("ls -d .");
print -+-$!;
print $!;
print -+-$!'
.
-1
33
No child processes
10


It seems that string-ifying "$!" changes its value.

[ikegami]

print can result in system calls. $! is meaningless after the first print.

$ perl -wle'
$SIG{CHLD}="IGNORE";
$! = 0;
my $rv = system("ls -d .");
my $errno = $!;
print $rv;
print 0+$errno;
print $errno;
print 0+$errno;
'
.
-1
10
No child processes
10

Note that 0+ is much easier to understand than -+-, and it conveys the intent much better.