Executing shell script with system() returns 256. What does that mean?

Question

I've written a shell script to soft-restart HAProxy (reverse proxy). Executing the script from the shell works. But I want a daemon to execute the script. That doesn't work. system() returns 256. I have no clue what that might mean.

#!/bin/sh # save previous state mv /home/haproxy/haproxy.cfg /home/haproxy/haproxy.cfg.old mv /var/run/haproxy.pid /var/run/haproxy.pid.old  cp /tmp/haproxy.cfg.new /home/haproxy/haproxy.cfg kill -TTOU $(cat /var/run/haproxy.pid.old) if haproxy -p /var/run/haproxy.pid -f /home/haproxy/haproxy.cfg; then   kill -USR1 $(cat /var/run/haproxy.pid.old)   rm -f /var/run/haproxy.pid.old   exit 1 else   kill -TTIN $(cat /var/run/haproxy.pid.old)   rm -f /var/run/haproxy.pid   mv /var/run/haproxy.pid.old /var/run/haproxy.pid   mv /home/haproxy/haproxy.cfg /home/haproxy/haproxy.cfg.err   mv /home/haproxy/haproxy.cfg.old /home/haproxy/haproxy.cfg   exit 0 fi 

HAProxy is executed with user haproxy. My daemon has it's own user too. Both run with sudo.

Any hints?

Answer 1

According to this and that, Perl's system() returns exit values multiplied by 256. So it's actually exiting with 1. It seems this happens in C too.

Answer 2

Unless system returns -1 its return value is of the same format as the status value from the wait family of system calls (man 2 wait). There are macros to help you interpret this status:

man 3 wait 

Lists these macros and what they tell you.