Inappropriate ioctl for device when changing egid in perl - perl

Question

I have a perl script that is executed by the Jenkins CI, but when it tries to execute the following code i get a "Inappropriate ioctl for device" error.
$) = $new_group;
if($!){
print STDERR $! . "\n";
print STDERR "Failure to change permissions to: Gid: $new_group \n";
next;
}
$> = $new_user;
if($!){
print STDERR $! . "\n";
print STDERR "Failure to change permissions to: Uid: $new_user \n";
next;
}
But while if a do the same manually like this, i receive no error
perl -e '$) = 99; if($!){print $! ."\n";} $> = 99; if($!){print $!."\n";}print `whoami`;'
Any clues why this error occures, and what i means? I have search the net, but it seems to occur when filehandlers are open, havnt seen any examples on it occuring when changing users.
All scripts are executed as root.

Answer 1

$! is only useful directly after a failed system call. When setting the group or user is successful, you don't really know what will be in $!, and can't rely on it being a false value. You might trying using 'or die ' when setting the user and group, or maybe just comparing $) and $> to $new_group and $new_user again after you attempt to set them.

Answer 2

To debug the code, use this method, and see whats going on. Print out each variable content when you receive an error. Please use strict and warnings, they heelp you a lot!
Please include the output if you cannot solve this problem with this method.
use strict;
use warnings;
use Data::Dumper;
$) = $new_group;
warn "\$), \$new_group: ".Dumper($),$new_group);
...