1GETNETENT(3) Linux Programmer's Manual GETNETENT(3)
2
6 getnetent, getnetbyname, getnetbyaddr, setnetent, endnetent - get net‐
7 work entry
8
10 #include <netdb.h>
11 struct netent *getnetent(void);
13 struct netent *getnetbyname(const char *name);
15 struct netent *getnetbyaddr(uint32_t net, int type);
17 void setnetent(int stayopen);
19 void endnetent(void);
21
23 The getnetent() function reads the next entry from the networks data‐
24 base and returns a netent structure containing the broken-out fields
25 from the entry. A connection is opened to the database if necessary.
26 The getnetbyname() function returns a netent structure for the entry
28 from the database that matches the network name.
29 The getnetbyaddr() function returns a netent structure for the entry
31 from the database that matches the network number net of type type.
32 The net argument must be in host byte order.
33 The setnetent() function opens a connection to the database, and sets
35 the next entry to the first entry. If stayopen is nonzero, then the
36 connection to the database will not be closed between calls to one of
37 the getnet*() functions.
38 The endnetent() function closes the connection to the database.
40 The netent structure is defined in <netdb.h> as follows:
42 struct netent {
44 char *n_name; /* official network name */
45 char **n_aliases; /* alias list */
46 int n_addrtype; /* net address type */
47 uint32_t n_net; /* network number */
48 }
49 The members of the netent structure are:
51 n_name The official name of the network.
53 n_aliases
55 A NULL-terminated list of alternative names for the network.
56 n_addrtype
58 The type of the network number; always AF_INET.
59 n_net The network number in host byte order.
61
63 The getnetent(), getnetbyname() and getnetbyaddr() functions return a
64 pointer to a statically allocated netent structure, or a null pointer
65 if an error occurs or the end of the file is reached.
66
68 /etc/networks
69 networks database file
70
72 For an explanation of the terms used in this section, see
73 attributes(7).
74 ┌───────────────┬───────────────┬───────────────────────────┐
76 │Interface │ Attribute │ Value │
77 ├───────────────┼───────────────┼───────────────────────────┤
78 │getnetent() │ Thread safety │ MT-Unsafe race:netent │
79 │ │ │ race:netentbuf env locale │
80 ├───────────────┼───────────────┼───────────────────────────┤
81 │getnetbyname() │ Thread safety │ MT-Unsafe race:netbyname │
82 │ │ │ env locale │
83 ├───────────────┼───────────────┼───────────────────────────┤
84 │getnetbyaddr() │ Thread safety │ MT-Unsafe race:netbyaddr │
85 │ │ │ locale │
86 ├───────────────┼───────────────┼───────────────────────────┤
87 │setnetent(), │ Thread safety │ MT-Unsafe race:netent env │
88 │endnetent() │ │ locale │
89 └───────────────┴───────────────┴───────────────────────────┘
90 In the above table, netent in race:netent signifies that if any of the
91 functions setnetent(), getnetent(), or endnetent() are used in parallel
92 in different threads of a program, then data races could occur.
93
95 POSIX.1-2001, POSIX.1-2008, 4.3BSD.
96
98 In glibc versions before 2.2, the net argument of getnetbyaddr() was of
99 type long.
100
102 getnetent_r(3), getprotoent(3), getservent(3)
103 RFC 1101
104
106 This page is part of release 4.16 of the Linux man-pages project. A
107 description of the project, information about reporting bugs, and the
108 latest version of this page, can be found at
109 https://www.kernel.org/doc/man-pages/.
110GNU 2017-09-15 GETNETENT(3)