getnetent, getnetbyaddr, getnetbyname, setnetent, endnetent - get networks entry
#include <netdb.h>
struct netent *getnetent()
struct
netent *getnetbyname(name)
char *name;
struct
netent *getnetbyaddr(net, type)
long net; int type;
void
setnetent(stayopen)
int stayopen;
void endnetent()
The getnetent, getnetbyname, and getnetbyaddr subroutines each return a pointer to an object with the following structure containing the broken-out fields of a line in the networks database.
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struct |
netent { |
||||||
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char |
*n_name; |
/* official name of net */ | |||||
|
char |
**n_aliases; |
/* alias list */ | |||||
|
int |
n_addrtype; |
/* net number type */ | |||||
|
long |
n_net; |
||||||
|
/* net number */ |
};
The members of this structure are:
|
n_name |
The official name of the network. | ||
|
n_aliases |
A zero terminated list of alternate names for the network. | ||
|
n_addrtype |
The type of the network number returned: AF_INET. | ||
|
n_net |
The network number. Network numbers are returned in machine byte order. |
If the stayopen flag on a setnetent subroutine is NULL, the networks database is opened. Otherwise the setnetent has the effect of rewinding the networks database. The endnetent may be called to close the networks database when processing is complete.
The getnetent subroutine simply reads the next line while getnetbyname and getnetbyaddr search until a matching name or net number is found (or until EOF is encountered). The type must be AF_INET. The getnetent subroutine keeps a pointer in the database, allowing successive calls to be used to search the entire file.
A call to setnetent must be made before a while loop using getnetent in order to perform initialization and an endnetent must be used after the loop. Both getnetbyname and getnetbyaddr make calls to setnetent and endnetent .
/etc/networks
Null pointer (0) returned on EOF or error.
networks(@FORMAT_EXT@)
RFC 1101
The getnetent(), getnetbyaddr(), getnetbyname(), setnetent(), and endnetent() functions appeared in 4.2BSD.
The data space used by these functions is static; if future use requires the data, it should be copied before any subsequent calls to these functions overwrite it. Only Internet network numbers are currently understood. Expecting network numbers to fit in no more than 32 bits is probably naive.