The /etc/protocols file contains information about the known protocols used in the DARPA (Defense Advanced Research Projects Agency) Internet. Each protocol is represented by a single line in the protocols file. Each entry is of the form: Name Number Aliases
The fields contain the following information: Official Internet protocol name. Protocol number. Unofficial names used for the protocol.
Items on a line are separated by one or more spaces or tab characters. Comments begin with the # (number sign), and routines that search the protocols file do not interpret characters from the beginning of a comment to the end of the line. A protocol name can contain any printable character except a field delimiter, newline character, or comment character.
The lines in the file appear as follows: # # Internet (IP) protocols # ip 0 IP # internet protocol, pseudo protocol number icmp 1 ICMP # internet control message protocol igmp 2 IGMP # internet group management protocol ggp 3 GGP # gateway-gateway protocol tcp 6 TCP # transmission control protocol egp 8 EGP # exterior gateway protocol pup 12 PUP # PARC universal packet protocol udp 17 UDP # user datagram protocol hmp 20 HMP # host monitoring protocol rdp 27 RDP # "reliable datagram" protocol
Functions: endprotoent(3), getprotobyname(3), getprotobynumber(3), getprotoent(3), setprotoent(3) delim off