We help IT Professionals succeed at work.

We've partnered with Certified Experts, Carl Webster and Richard Faulkner, to bring you a podcast all about Citrix Workspace, moving to the cloud, and analytics & intelligence. Episode 2 coming soon!Listen Now

x

C CGI Program system call problem

kuang
kuang asked
on
Medium Priority
246 Views
Last Modified: 2013-12-25
I have a problem with my C cgi program on my NCSA HTTPD v1.5.
THe code look like:
fail = system("the_program_need_to_be_executed 1>/dev/null 2>/dev/null");
printf("show the fail value %d<P>",fail);
if (!fail)
        ............;

else
        ............;

The system call will return 0 if it is successful.
If I ran it from command line, it takes less then 1 sec to finish it.
When I ran it from the browser, it does not print the line.  THe browser seems
to wait for a long time.  I check the process status, the fork child processes
still sittng there.  How can I solve the problem and how can I trap it?

Thank you


                                                                     
                                                         
Comment
Watch Question

Commented:

When you run the script from the prompt, it is run with your uid. The server probably runs with uid 'nobody'. Could that be your problem?

If not, you'll have to be more specific: Does the cgi work at all? Say, does it work if your remove the line 'fail=system...'?
Also, try piping stdout and stderr into a file (eg /tmp/debug) and tell us what you see.

 cheers,

   Philippe


Not the solution you were looking for? Getting a personalized solution is easy.

Ask the Experts

Author

Commented:
I did ran a test(non cgi) as nobody(web uid).  it works.
I did run that cgi program and try to pipe the stdout and stderr to files which have been generateed but nothing in side the files.

If I comment the system call out it ran ok.

is there anything I can try further?

Thank you

ozo
CERTIFIED EXPERT
Most Valuable Expert 2014
Top Expert 2015

Commented:
Could path be set differently when you run as nobody and
when the server runs your program?
Did you try specifying the full pathname to the_program_need_to_be_executed?

Commented:

Kuang,

so we have a program which generates no output, works fine when you run it from prompt and blocks without givin an error message when run from the server.

Did you try ozo's comment? To have the same environment as nobody
would have ,try a 'su - nobody' (the '-' says that you also want to change the environment). You should then be in exactly the same situation as the browser.

Is there any chance that the machine on which you test your script and the machine on which the server runs are not the same?

What does your program actually do? Is it a script or a program you wrote. Does it access any remote files or do something it could need permission for? If you have access to the source of that program you could have it print out some debug information.

We might be able to help you more if you tell us more about that program.

  cheers,

   Philippe

Access more of Experts Exchange with a free account
Thanks for using Experts Exchange.

Create a free account to continue.

Limited access with a free account allows you to:

  • View three pieces of content (articles, solutions, posts, and videos)
  • Ask the experts questions (counted toward content limit)
  • Customize your dashboard and profile

*This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.

OR

Please enter a first name

Please enter a last name

8+ characters (letters, numbers, and a symbol)

By clicking, you agree to the Terms of Use and Privacy Policy.