The `ping' command allows the user to check if another system is currently "up" and running. The general form of the command is `ping system'.(11) For example,
will tell you if the main machine in Widener University's Computer Science lab is currently online (we certainly hope so!).
Many implementations of `ping' also include an option to let you see how fast a link is running (to give you some idea of the load on the network). For example:
% ping -s cs.swarthmore.edu PING cs.swarthmore.edu: 56 data bytes 64 bytes from 220.127.116.11: icmp_seq=0 ttl=251 time=66 ms 64 bytes from 18.104.22.168: icmp_seq=1 ttl=251 time=45 ms 64 bytes from 22.214.171.124: icmp_seq=2 ttl=251 time=46 ms ^C --- cs.swarthmore.edu ping statistics --- 3 packets transmitted, 3 packets received, 0% packet loss round-trip min/avg/max = 45/52/66 ms
This case tells us that for `cs.swarthmore.edu' it takes about 46 milliseconds for a packet to go from Widener to Swarthmore College and back again. It also gives the average and worst-case speeds, and any packet loss that may have occurred (e.g. because of network congestion).
While `ping' generally doesn't hurt network performance, you shouldn't use it too often--usually once or twice will leave you relatively sure of the other system's state.
Copyright © 1998, Software Engineering Laboratory
National Technical University of Athens