getnetent(3)

1getnetent(3)               Library Functions Manual               getnetent(3)
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NAME

6       getnetent,  getnetbyname, getnetbyaddr, setnetent, endnetent - get net‐
7       work entry
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LIBRARY

10       Standard C library (libc, -lc)
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SYNOPSIS

13       #include <netdb.h>
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15       struct netent *getnetent(void);
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17       struct netent *getnetbyname(const char *name);
18       struct netent *getnetbyaddr(uint32_t net, int type);
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20       void setnetent(int stayopen);
21       void endnetent(void);
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DESCRIPTION

24       The getnetent() function reads the next entry from the  networks  data‐
25       base  and  returns  a netent structure containing the broken-out fields
26       from the entry.  A connection is opened to the database if necessary.
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28       The getnetbyname() function returns a netent structure  for  the  entry
29       from the database that matches the network name.
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31       The  getnetbyaddr()  function  returns a netent structure for the entry
32       from the database that matches the network number  net  of  type  type.
33       The net argument must be in host byte order.
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35       The  setnetent()  function opens a connection to the database, and sets
36       the next entry to the first entry.  If stayopen is  nonzero,  then  the
37       connection  to  the database will not be closed between calls to one of
38       the getnet*() functions.
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40       The endnetent() function closes the connection to the database.
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42       The netent structure is defined in <netdb.h> as follows:
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44           struct netent {
45               char      *n_name;     /* official network name */
46               char     **n_aliases;  /* alias list */
47               int        n_addrtype; /* net address type */
48               uint32_t   n_net;      /* network number */
49           }
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51       The members of the netent structure are:
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53       n_name The official name of the network.
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55       n_aliases
56              A NULL-terminated list of alternative names for the network.
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58       n_addrtype
59              The type of the network number; always AF_INET.
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61       n_net  The network number in host byte order.
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RETURN VALUE

64       The getnetent(), getnetbyname(), and getnetbyaddr() functions return  a
65       pointer  to  a statically allocated netent structure, or a null pointer
66       if an error occurs or the end of the file is reached.
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FILES

69       /etc/networks
70              networks database file
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ATTRIBUTES

73       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
74       tributes(7).
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76       ┌───────────────┬───────────────┬──────────────────────────────────────┐
77       │Interface      │ Attribute     │ Value                                │
78       ├───────────────┼───────────────┼──────────────────────────────────────┤
79       │getnetent()    │ Thread safety │ MT-Unsafe race:netent race:netentbuf │
80       │               │               │ env locale                           │
81       ├───────────────┼───────────────┼──────────────────────────────────────┤
82       │getnetbyname() │ Thread safety │ MT-Unsafe race:netbyname env locale  │
83       ├───────────────┼───────────────┼──────────────────────────────────────┤
84       │getnetbyaddr() │ Thread safety │ MT-Unsafe race:netbyaddr locale      │
85       ├───────────────┼───────────────┼──────────────────────────────────────┤
86       │setnetent(),   │ Thread safety │ MT-Unsafe race:netent env locale     │
87       │endnetent()    │               │                                      │
88       └───────────────┴───────────────┴──────────────────────────────────────┘
89       In  the above table, netent in race:netent signifies that if any of the
90       functions setnetent(), getnetent(), or endnetent() are used in parallel
91       in different threads of a program, then data races could occur.
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STANDARDS

94       POSIX.1-2008.
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HISTORY

97       POSIX.1-2001, 4.3BSD.
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99       Before glibc 2.2, the net argument of getnetbyaddr() was of type long.
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