mirror of https://github.com/mkerrisk/man-pages
212 lines
4.5 KiB
Groff
212 lines
4.5 KiB
Groff
.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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.\"
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.\" %%%LICENSE_START(VERBATIM)
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\" %%%LICENSE_END
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.\"
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.\" References consulted:
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.\" Linux libc source code
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.\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
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.\" 386BSD man pages
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.\" Modified Sat Jul 24 21:48:06 1993 by Rik Faith (faith@cs.unc.edu)
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.TH GETNETENT 3 2020-12-21 "GNU" "Linux Programmer's Manual"
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.SH NAME
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getnetent, getnetbyname, getnetbyaddr, setnetent, endnetent \-
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get network entry
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.SH SYNOPSIS
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.nf
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.B #include <netdb.h>
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.PP
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.B struct netent *getnetent(void);
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.PP
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.BI "struct netent *getnetbyname(const char *" name );
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.PP
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.BI "struct netent *getnetbyaddr(uint32_t " net ", int " type );
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.PP
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.BI "void setnetent(int " stayopen );
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.PP
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.B void endnetent(void);
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.fi
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.SH DESCRIPTION
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The
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.BR getnetent ()
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function reads the next entry from the networks database
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and returns a
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.I netent
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structure containing
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the broken-out fields from the entry.
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A connection is opened to the database if necessary.
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.PP
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The
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.BR getnetbyname ()
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function returns a
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.I netent
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structure
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for the entry from the database
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that matches the network
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.IR name .
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.PP
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The
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.BR getnetbyaddr ()
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function returns a
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.I netent
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structure
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for the entry from the database
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that matches the network number
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.I net
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of type
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.IR type .
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The
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.I net
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argument must be in host byte order.
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.PP
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The
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.BR setnetent ()
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function opens a connection to the database,
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and sets the next entry to the first entry.
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If
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.I stayopen
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is nonzero,
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then the connection to the database
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will not be closed between calls to one of the
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.BR getnet* ()
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functions.
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.PP
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The
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.BR endnetent ()
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function closes the connection to the database.
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.PP
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The
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.I netent
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structure is defined in
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.I <netdb.h>
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as follows:
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.PP
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.in +4n
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.EX
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struct netent {
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char *n_name; /* official network name */
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char **n_aliases; /* alias list */
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int n_addrtype; /* net address type */
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uint32_t n_net; /* network number */
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}
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.EE
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.in
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.PP
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The members of the
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.I netent
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structure are:
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.TP
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.I n_name
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The official name of the network.
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.TP
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.I n_aliases
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A NULL-terminated list of alternative names for the network.
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.TP
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.I n_addrtype
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The type of the network number; always
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.BR AF_INET .
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.TP
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.I n_net
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The network number in host byte order.
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.SH RETURN VALUE
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The
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.BR getnetent (),
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.BR getnetbyname (),
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and
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.BR getnetbyaddr ()
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functions return a pointer to a
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statically allocated
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.I netent
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structure, or a null pointer if an
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error occurs or the end of the file is reached.
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.SH FILES
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.TP
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.I /etc/networks
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networks database file
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.SH ATTRIBUTES
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For an explanation of the terms used in this section, see
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.BR attributes (7).
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.TS
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allbox;
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lbw14 lb lbw25
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l l l.
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Interface Attribute Value
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T{
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.BR getnetent ()
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T} Thread safety T{
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MT-Unsafe race:netent
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.br
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race:netentbuf env locale
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T}
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T{
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.BR getnetbyname ()
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T} Thread safety T{
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MT-Unsafe race:netbyname
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.br
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env locale
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T}
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T{
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.BR getnetbyaddr ()
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T} Thread safety T{
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MT-Unsafe race:netbyaddr
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.br
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locale
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T}
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T{
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.BR setnetent (),
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.br
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.BR endnetent ()
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T} Thread safety T{
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MT-Unsafe race:netent env
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.br
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locale
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T}
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.TE
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.sp 1
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In the above table,
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.I netent
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in
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.I race:netent
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signifies that if any of the functions
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.BR setnetent (),
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.BR getnetent (),
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or
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.BR endnetent ()
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are used in parallel in different threads of a program,
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then data races could occur.
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.SH CONFORMING TO
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POSIX.1-2001, POSIX.1-2008, 4.3BSD.
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.SH NOTES
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In glibc versions before 2.2, the
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.I net
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argument of
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.BR getnetbyaddr ()
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was of type
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.IR long .
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.SH SEE ALSO
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.BR getnetent_r (3),
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.BR getprotoent (3),
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.BR getservent (3)
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.\" .BR networks (5)
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.br
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RFC\ 1101
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