Question

Let’s suppose we have a code doing something like this:

int pipes[2];
pipe(pipes);
pid_t p = fork();
if(0 == p)
{
   dup2(pipes[1], STDOUT_FILENO);
   execv("/path/to/my/program", NULL);
   ...
}
else
{
//... parent process stuff
}

As you can see, it’s creating a pipe, forking and using the pipe to read the child’s output (I can’t use popen here, because I also need the PID of the child process for other purposes).

Question is, what should happen if in the above code, execv fails? Should I call exit() or abort()? As far as I know, those functions close the open file descriptors. Since fork-ed process inherits the parent’s file descriptors, does it mean that the file descriptors used by the parent process will become unusable?

UPD

I want to emphasize that the question is not about the executable loaded by exec() failing, but exec itself, e.g. in case the file referred by the first argument is not found or is not executable.

Answer 1

You should use exit(int) since the (low byte) of the argument can be read by the parent process using waitpid(). This lets you handle the error appropriately in the parent process. Depending on what your program does you may want to use _exit instead of exit. The difference is that _exit will not run functions registered with atexit nor will it flush stdio streams.