Others have answered what the 8 means, you might also want to know why it's used, since it may be "obvious" that traceroute is a system utility. In many cases i

Others have answered what the 8 means, you might also want to know why it's used, since it may be "obvious" that traceroute is a system utility. In many cases it's not obvious whether one is referring to the syscall, kernel API, system utility, etc, since overloading a single simple word is quite common.