The man page of my linux (Ubuntu), does not mention the need of NULL as last parameter, the man page of a minix version `execl` mentions the need of NULL as last parameter. Yet, I had strange behavior while invoking `modprobe` that I solved putting NULL as last parameter.

The way that worked for me:

```
execl("/sbin/modprobe","modprobe","pl2303",NULL);

```

While if I do it this way:

```
execl("/sbin/modprobe","modprobe","pl2303")

```

I get an error no 14 (EFAULT).`