Get parent process id for specific process

getppid_for_process.c

pid_t getppid_for_process(pid_t pid) {
#if defined(__APPLE__)
	struct kinfo_proc info;
	size_t length = sizeof(struct kinfo_proc);
	int mib[4] = { CTL_KERN, KERN_PROC, KERN_PROC_PID, pid };
	if (sysctl(mib, 4, &info, &length, NULL, 0) < 0)
		return -1;
	if (length == 0)
		return -1;
	return info.kp_eproc.e_ppid;
#elif defined(__linux__)
	char proc_filepath[BUFSIZE];
	char buffer[BUFSIZE];
	pid_t parent = -1;
	memset(proc_filepath, 0, BUFSIZE);
	snprintf(proc_filepath, BUFSIZE, "/proc/%d/status", pid);
	FILE * fp = fopen(proc_filepath, "r");
	while (fgets(buffer, BUFSIZE, fp) != NULL) {
		if(strncmp(buffer, "PPid:", 5) == 0) {
			sscanf(buffer, "PPid: %d", &parent);
			break;
		}
	}
	fclose(fp);
	return parent;
#endif /* __linux__ */
}