code:

pid_t pid = fork();

if(isErrorProc(pid))
{
printf("This message means it failed to create a process\n");
exit(1);
}

if(isMainProc(pid))
{
wait( (int*)0 ); // wait for created process has been finished.

/* Do something herefor stdout/stderr generated by child process*/

exit(0);
}

if(isChildProc(pid))
{
execl("/bin/ls", "ls", "-la", ">", "log.txt", (char*)0);
printf("This message means system call *execl()* failed\n");
exit(1);
}

code:

freopen("stdout.log", "w", stdout); // redirect stdoutput to a file
named "stdout.log"
freopen("stderr.log", "w", stderr);   // redirect stderror to a file
named "stderr.log"

system("cc SomeSourceFile.c"); // the output message will be redirect
to a corresponding file