man3/getnetent.3

   1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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  25 .\" References consulted:
  26 .\"     Linux libc source code
  27 .\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
  28 .\"     386BSD man pages
  29 .\" Modified Sat Jul 24 21:48:06 1993 by Rik Faith (faith@cs.unc.edu)
  30 .TH GETNETENT 3  2016-10-08 "GNU" "Linux Programmer's Manual"
  31 .SH NAME
  32 getnetent, getnetbyname, getnetbyaddr, setnetent, endnetent \-
  33 get network entry
  34 .SH SYNOPSIS
  35 .nf
  36 .B #include <netdb.h>
  37 .sp
  38 .B struct netent *getnetent(void);
  39 .sp
  40 .BI "struct netent *getnetbyname(const char *" name );
  41 .sp
  42 .BI "struct netent *getnetbyaddr(uint32_t " net ", int " type );
  43 .sp
  44 .BI "void setnetent(int " stayopen );
  45 .sp
  46 .B void endnetent(void);
  47 .fi
  48 .SH DESCRIPTION
  49 The
  50 .BR getnetent ()
  51 function reads the next entry from the networks database
  52 and returns a
  53 .I netent
  54 structure containing
  55 the broken-out fields from the entry.
  56 A connection is opened to the database if necessary.
  57 .PP
  58 The
  59 .BR getnetbyname ()
  60 function returns a
  61 .I netent
  62 structure
  63 for the entry from the database
  64 that matches the network
  65 .IR name .
  66 .PP
  67 The
  68 .BR getnetbyaddr ()
  69 function returns a
  70 .I netent
  71 structure
  72 for the entry from the database
  73 that matches the network number
  74 .I net
  75 of type
  76 .IR type .
  77 The
  78 .I net
  79 argument must be in host byte order.
  80 .PP
  81 The
  82 .BR setnetent ()
  83 function opens a connection to the database,
  84 and sets the next entry to the first entry.
  85 If
  86 .I stayopen
  87 is nonzero,
  88 then the connection to the database
  89 will not be closed between calls to one of the
  90 .BR getnet* ()
  91 functions.
  92 .PP
  93 The
  94 .BR endnetent ()
  95 function closes the connection to the database.
  96 .PP
  97 The
  98 .I netent
  99 structure is defined in
 100 .I <netdb.h>
 101 as follows:
 102 .sp
 103 .in +4n
 104 .nf
 105 struct netent {
 106     char      *n_name;     /* official network name */
 107     char     **n_aliases;  /* alias list */
 108     int        n_addrtype; /* net address type */
 109     uint32_t   n_net;      /* network number */
 110 }
 111 .fi
 112 .in
 113 .PP
 114 The members of the
 115 .I netent
 116 structure are:
 117 .TP
 118 .I n_name
 119 The official name of the network.
 120 .TP
 121 .I n_aliases
 122 A NULL-terminated list of alternative names for the network.
 123 .TP
 124 .I n_addrtype
 125 The type of the network number; always
 126 .BR AF_INET .
 127 .TP
 128 .I n_net
 129 The network number in host byte order.
 130 .SH RETURN VALUE
 131 The
 132 .BR getnetent (),
 133 .BR getnetbyname ()
 134 and
 135 .BR getnetbyaddr ()
 136 functions return a pointer to a
 137 statically allocated
 138 .I netent
 139 structure, or a null pointer if an
 140 error occurs or the end of the file is reached.
 141 .SH FILES
 142 .TP
 143 .I /etc/networks
 144 networks database file
 145 .SH ATTRIBUTES
 146 For an explanation of the terms used in this section, see
 147 .BR attributes (7).
 148 .TS
 149 allbox;
 150 lbw14 lb lbw25
 151 l l l.
 152 Interface       Attribute       Value
 153 T{
 154 .BR getnetent ()
 155 T}      Thread safety   T{
 156 MT-Unsafe race:netent
 157 .br
 158 race:netentbuf env locale
 159 T}
 160 T{
 161 .BR getnetbyname ()
 162 T}      Thread safety   T{
 163 MT-Unsafe race:netbyname
 164 .br
 165 env locale
 166 T}
 167 T{
 168 .BR getnetbyaddr ()
 169 T}      Thread safety   T{
 170 MT-Unsafe race:netbyaddr
 171 .br
 172 locale
 173 T}
 174 T{
 175 .BR setnetent (),
 176 .br
 177 .BR endnetent ()
 178 T}      Thread safety   T{
 179 MT-Unsafe race:netent env
 180 .br
 181 locale
 182 T}
 183 .TE
 184
 185 In the above table,
 186 .I netent
 187 in
 188 .I race:netent
 189 signifies that if any of the functions
 190 .BR setnetent (),
 191 .BR getnetent (),
 192 or
 193 .BR endnetent ()
 194 are used in parallel in different threads of a program,
 195 then data races could occur.
 196 .SH CONFORMING TO
 197 POSIX.1-2001, POSIX.1-2008, 4.3BSD.
 198 .SH NOTES
 199 In glibc versions before 2.2, the
 200 .I net
 201 argument of
 202 .BR getnetbyaddr ()
 203 was of type
 204 .IR long .
 205 .SH SEE ALSO
 206 .BR getnetent_r (3),
 207 .BR getprotoent (3),
 208 .BR getservent (3)
 209 .\" .BR networks (5)
 210 .br
 211 RFC\ 1101