GETNETENT

Section: C Library Functions (3)
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BSD mandoc
BSD 4  

NAME

getnetent getnetbyaddr getnetbyname setnetent endnetent - get networks entry  

SYNOPSIS

Fd #include <netdb.h> Ft struct netent * Fn getnetent Ft struct netent * Fn getnetbyname char name Ft struct netent * Fn getnetbyaddr unsigned long net int type Ft void Fn setnetent int stayopen Ft void Fn endnetent  

DESCRIPTION

The Fn getnetent , Fn getnetbyname , and Fn 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.
struct  netent {
        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 Fa stayopen flag on a Fn setnetent subroutine is NULL, the networks database is opened. Otherwise, the Fn setnetent has the effect of rewinding the networks database. The Fn endnetent subroutine may be called to close the networks database when processing is complete.

The Fn getnetent subroutine simply reads the next line while Fn getnetbyname and Fn getnetbyaddr search until a matching Fa name or Fa net number is found (or until EOF is encountered). The Fa type must be AF_INET The Fn getnetent subroutine keeps a pointer in the database, allowing successive calls to be used to search the entire file.

Before a while loop using Fn getnetent , a call to Fn setnetent must be made in order to perform initialization; a call to Fn endnetent must be used after the loop. Both Fn getnetbyname and Fn getnetbyaddr make calls to Fn setnetent and Fn endnetent .  

FILES

/etc/networks  

DIAGNOSTICS

Null pointer (0) returned on EOF or error.  

SEE ALSO

networks(5), RFC 1101.  

HISTORY

The Fn getnetent , Fn getnetbyaddr , Fn getnetbyname , Fn setnetent , and Fn endnetent functions appeared in BSD 4.2  

BUGS

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.


 

Index

NAME
SYNOPSIS
DESCRIPTION
FILES
DIAGNOSTICS
SEE ALSO
HISTORY
BUGS

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