man3/getservent.3

.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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.\" References consulted:
.\"     Linux libc source code
.\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
.\"     386BSD man pages
.\" Modified Sat Jul 24 19:19:11 1993 by Rik Faith (faith@cs.unc.edu)
.\" Modified Wed Oct 18 20:23:54 1995 by Martin Schulze <joey@infodrom.north.de>
.\" Modified Mon Apr 22 01:50:54 1996 by Martin Schulze <joey@infodrom.north.de>
.\" 2001-07-25 added a clause about NULL proto (Martin Michlmayr or David N. Welton)
.\"
.TH GETSERVENT 3  2021-03-22 "GNU" "Linux Programmer's Manual"
.SH NAME
getservent, getservbyname, getservbyport, setservent, endservent \-
get service entry
.SH SYNOPSIS
.nf
.B #include <netdb.h>
.PP
.B struct servent *getservent(void);
.PP
.BI "struct servent *getservbyname(const char *" name ", const char *" proto );
.BI "struct servent *getservbyport(int " port ", const char *" proto );
.PP
.BI "void setservent(int " stayopen );
.B void endservent(void);
.fi
.SH DESCRIPTION
The
.BR getservent ()
function reads the next entry from the services database (see
.BR services (5))
and returns a
.I servent
structure containing
the broken-out fields from the entry.
A connection is opened to the database if necessary.
.PP
The
.BR getservbyname ()
function returns a
.I servent
structure
for the entry from the database
that matches the service
.I name
using protocol
.IR proto .
If
.I proto
is NULL, any protocol will be matched.
A connection is opened to the database if necessary.
.PP
The
.BR getservbyport ()
function returns a
.I servent
structure
for the entry from the database
that matches the port
.I port
(given in network byte order)
using protocol
.IR proto .
If
.I proto
is NULL, any protocol will be matched.
A connection is opened to the database if necessary.
.PP
The
.BR setservent ()
function opens a connection to the database,
and sets the next entry to the first entry.
If
.I stayopen
is nonzero,
then the connection to the database
will not be closed between calls to one of the
.BR getserv* ()
functions.
.PP
The
.BR endservent ()
function closes the connection to the database.
.PP
The
.I servent
structure is defined in
.I <netdb.h>
as follows:
.PP
.in +4n
.EX
struct servent {
    char  *s_name;       /* official service name */
    char **s_aliases;    /* alias list */
    int    s_port;       /* port number */
    char  *s_proto;      /* protocol to use */
}
.EE
.in
.PP
The members of the
.I servent
structure are:
.TP
.I s_name
The official name of the service.
.TP
.I s_aliases
A NULL-terminated list of alternative names for the service.
.TP
.I s_port
The port number for the service given in network byte order.
.TP
.I s_proto
The name of the protocol to use with this service.
.SH RETURN VALUE
The
.BR getservent (),
.BR getservbyname (),
and
.BR getservbyport ()
functions return a pointer to a
statically allocated
.I servent
structure, or NULL if an
error occurs or the end of the file is reached.
.SH FILES
.TP
.I /etc/services
services database file
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.ad l
.nh
.TS
allbox;
lb lb lbx
l l l.
Interface	Attribute	Value
T{
.BR getservent ()
T}	Thread safety	T{
MT-Unsafe race:servent
race:serventbuf locale
T}
T{
.BR getservbyname ()
T}	Thread safety	T{
MT-Unsafe race:servbyname
locale
T}
T{
.BR getservbyport ()
T}	Thread safety	T{
MT-Unsafe race:servbyport
locale
T}
T{
.BR setservent (),
.BR endservent ()
T}	Thread safety	T{
MT-Unsafe race:servent
locale
T}
.TE
.hy
.ad
.sp 1
In the above table,
.I servent
in
.I race:servent
signifies that if any of the functions
.BR setservent (),
.BR getservent (),
or
.BR endservent ()
are used in parallel in different threads of a program,
then data races could occur.
.SH CONFORMING TO
POSIX.1-2001, POSIX.1-2008, 4.3BSD.
.SH SEE ALSO
.BR getnetent (3),
.BR getprotoent (3),
.BR getservent_r (3),
.BR services (5)