'\" t
.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.\" References consulted:
.\"     Linux libc source code
.\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
.\"     386BSD man pages
.\" Modified Sat Jul 24 19:26:03 1993 by Rik Faith (faith@cs.unc.edu)
.TH getprotoent 3 2023-10-31 "Linux man-pages 6.06"
.SH NAME
getprotoent, getprotobyname, getprotobynumber, setprotoent,
endprotoent \- get protocol entry
.SH LIBRARY
Standard C library
.RI ( libc ", " \-lc )
.SH SYNOPSIS
.nf
.B #include <netdb.h>
.P
.B struct protoent *getprotoent(void);
.P
.BI "struct protoent *getprotobyname(const char *" name );
.BI "struct protoent *getprotobynumber(int " proto );
.P
.BI "void setprotoent(int " stayopen );
.B void endprotoent(void);
.fi
.SH DESCRIPTION
The
.BR getprotoent ()
function reads the next entry from the protocols database (see
.BR protocols (5))
and returns a
.I protoent
structure
containing the broken-out fields from the entry.
A connection is opened to the database if necessary.
.P
The
.BR getprotobyname ()
function returns a
.I protoent
structure
for the entry from the database
that matches the protocol name
.IR name .
A connection is opened to the database if necessary.
.P
The
.BR getprotobynumber ()
function returns a
.I protoent
structure
for the entry from the database
that matches the protocol number
.IR number .
A connection is opened to the database if necessary.
.P
The
.BR setprotoent ()
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 getproto* ()
functions.
.P
The
.BR endprotoent ()
function closes the connection to the database.
.P
The
.I protoent
structure is defined in
.I <netdb.h>
as follows:
.P
.in +4n
.EX
struct protoent {
    char  *p_name;       /* official protocol name */
    char **p_aliases;    /* alias list */
    int    p_proto;      /* protocol number */
}
.EE
.in
.P
The members of the
.I protoent
structure are:
.TP
.I p_name
The official name of the protocol.
.TP
.I p_aliases
A NULL-terminated list of alternative names for the protocol.
.TP
.I p_proto
The protocol number.
.SH RETURN VALUE
The
.BR getprotoent (),
.BR getprotobyname (),
and
.BR getprotobynumber ()
functions return a pointer to a
statically allocated
.I protoent
structure, or a null pointer if an
error occurs or the end of the file is reached.
.SH FILES
.PD 0
.TP
.I /etc/protocols
protocol database file
.PD
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lb lb lbx
l l l.
Interface	Attribute	Value
T{
.na
.nh
.BR getprotoent ()
T}	Thread safety	T{
.na
.nh
MT-Unsafe race:protoent
race:protoentbuf locale
T}
T{
.na
.nh
.BR getprotobyname ()
T}	Thread safety	T{
.na
.nh
MT-Unsafe race:protobyname
locale
T}
T{
.na
.nh
.BR getprotobynumber ()
T}	Thread safety	T{
.na
.nh
MT-Unsafe race:protobynumber
locale
T}
T{
.na
.nh
.BR setprotoent (),
.BR endprotoent ()
T}	Thread safety	T{
.na
.nh
MT-Unsafe race:protoent
locale
T}
.TE
.P
In the above table,
.I protoent
in
.I race:protoent
signifies that if any of the functions
.BR setprotoent (),
.BR getprotoent (),
or
.BR endprotoent ()
are used in parallel in different threads of a program,
then data races could occur.
.SH STANDARDS
POSIX.1-2008.
.SH HISTORY
POSIX.1-2001, 4.3BSD.
.SH SEE ALSO
.BR getnetent (3),
.BR getprotoent_r (3),
.BR getservent (3),
.BR protocols (5)