how to detect failure of system call if & is added to the command

[wontian]

Hi, folks,

Can anyone help me to figure out a way to detect the failure of system call in c/c++ code if the command is suggested to run in the way like "firefox index.html &", src code might be like:

int ret = system("firefox index.html &");

failure could take place if firefox is not installed or index.html does not exist. More, '&' charactor has to be added for the program need to go on running after the code is triggered.

I am a student and working on a program project, finding that system is related to fork information. However, & will make fork success but acturally may fail.

Great Thanks!

[keikun2004]

It is better to use fork and an IPC system than use just system call in your case.
But if you want to stick with your system call solution with '&', you can make it like this :
int ret = system("(firefox index.html; echo $?>/tmp/errcode) &");
and then try to read /tmp/errcode file with a timeout. If the timeout is reached and there is no file, then the command is a success, if the file was found before timeout, if it contains 0 then the command was successfull else it is a failure.

[Rubberman]

I agree with keikun2004 that it is better to fork, and then use one of the exec() calls in the child process. You can then use one of the wait() calls in the parent with the WNOHANG options (returns immediately, not blocking execution of the parent process) when you want, allowing you to continue with other stuff, and when wait() returns with a 0 status, then you can get the exit status and/or other information if desired, such as whether or not the child process dumped core, was signalled, etc.