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.\"     @(#)services.5	8.1 (Berkeley) 6/5/93
.\"
.Dd $Mdocdate: May 5 2021 $
.Dt SERVICES 5
.Os
.Sh NAME
.Nm services
.Nd service name database
.Sh DESCRIPTION
The
.Nm
file contains information regarding the known services available in the
Internet.
For each service, a single line should be present with the
following information:
.Bd -unfilled -offset indent
official service name
port number
protocol name
aliases
.Ed
.Pp
Items are separated by any number of blanks and/or tab characters.
The port number and protocol name are considered a single item; a slash
.Pq Ql /
is used to separate the port and protocol (e.g.,
.Dq 512/tcp ) .
.Pp
A hash mark
.Pq Ql #
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.
.Pp
Service names may contain any printable character other than a
field delimiter, newline, or comment character.
.Pp
To protect service ports from being used for dynamic port assignment,
.Xr rc 8
reads
.Nm
at boot and uses the contents to populate
.Va net.inet.tcp.baddynamic
and
.Va net.inet.udp.baddynamic .
.Pp
While it is the policy of IANA to assign a single well-known port number
for both TCP and UDP, to avoid reducing the dynamic port range unnecessarily,
the unused entries are not always listed in
.Nm .
.Sh FILES
.Bl -tag -width /etc/services -compact
.It Pa /etc/services
.El
.Sh SEE ALSO
.Xr getservent 3
.Sh HISTORY
The
.Nm
file format appeared in
.Bx 4.2 .
.Sh BUGS
A name server should be used instead of a static file.
Lines in
.Pa /etc/services
are limited to
.Dv BUFSIZ
characters (currently 1024).
Longer lines will be ignored.