The services file contains information regarding the known services available in the Internet. For each service a single line should be present with the following information:
official service name
Items are separated by any number of blanks and/or tab characters. The port number and protocol name are considered a single item; a / is used to separate the port and protocol (e.g. 512/tcp). A # indicates the beginning of a comment; subsequent characters up to the end of the line are not interpreted by the routines which search the file.
Service names may contain any printable character other than a field delimiter, newline, or comment character.
Access to the NIS services.byname map can be enabled by adding a single + on a line by itself in the /etc/services file. This causes the contents of the NIS services map to be inserted at the location where the + appears.