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I had received some help in the forum for the issue when I posted it last time. But the suggestions could not clear the problems. The case is as follows I have written a program for scada application. I used a script to automatically start it at run-level 5. Now, the program gets executed at boot time. It forks into memory and stays active. It works fine and reports issues to syslog. But, xmessage command does not work!! I am trying it in Suse and program was written is C. It just invokes system(xmessage(mymsgstring)) but xmessages do not pop-up at all. But if I execute the same script in terminal or just by doubleclicking it, xmessage works fine and the messages pop-up properly. To this problem I was advised to set the display variables, and I tried the suggestions. First, I tried to change the DISPLAY environment in the script. I used the command env|grep DISPLAY >/dev/null || { DISPLAY=:0.0; export DISPLAY; } in the script that is executed by the start-up script and also in the startup script. #!/bin/sh was used for running. Script did not give any errors. But xmessage doesn't work!!! No pop ups came!! 1. I inserted the line " env|grep DISPLAY >/dev/null || { DISPLAY=:0.0; export DISPLAY; } " both in the startup script and the actual script that is run by the startup script. 2. I also tried removing the second script altogether and directly running the program in the start up script. 3. I again tried removing the line from the start-up script and using it only in the script run by the startup script. 4. I further tried running the scripts immediately after booting, ie: in boot.local file. But nothing works. Scripts are run at runlevel 5. The program works fine except for the xmessage. It reports issues to syslog also correctly. If I kill the program after startup and then execute it again manually, messages also pop up correctly. Then I tried modifying the c program. I found out that, even after inserting putenv("DISPLAY=:0.0") in my c program, xmessage doesn't work. Actually, program exits the parent and forks into a daemon that scans the port to which a scada controller is connected. putenv("DISPLAY=:0.0") was inserted at the entry point in the parent, and even in the entry point in the child. program compiles fine without any errors or warnings, but xmessage doesn't work!! Everything else works correctly. But, as I mentioned, if I kill the program after startup and then execute it again manually, messages pop up correctly. Any suggestions would be of great help.