NAME

endnetent, getnetbyaddr, getnetbyname, getnetent, setnetent — network database functions

SYNOPSIS

#include <netdb.h>

void endnetent(void);
struct netent *getnetbyaddr(uint32_t net, int type);
struct netent *getnetbyname(const char *name);
struct netent *getnetent(void);
void setnetent(int stayopen);


DESCRIPTION

These functions shall retrieve information about networks. This information is considered to be stored in a database that can be accessed sequentially or randomly. The implementation of this database is unspecified.

The setnetent() function shall open and rewind the database. If the stayopen argument is non-zero, the connection to the net database shall not be closed after each call to getnetent() (either directly, or indirectly through one of the other getnet*() functions), and the implementation may maintain an open file descriptor to the database. If a file descriptor is used, the FD_CLOEXEC flag shall be set; see <fcntl.h>.

The getnetent() function shall read the next entry of the database, opening and closing a connection to the database as necessary.

The getnetbyaddr() function shall search the database from the beginning, and find the first entry for which the address family specified by type matches the n_addrtype member and the network number net matches the n_net member, opening and closing a connection to the database as necessary. The net argument shall be the network number in host byte order.

The getnetbyname() function shall search the database from the beginning and find the first entry for which the network name specified by name matches the n_name member, opening and closing a connection to the database as necessary.

The getnetbyaddr(), getnetbyname(), and getnetent() functions shall each return a pointer to a netent structure, the members of which shall contain the fields of an entry in the network database.

The endnetent() function shall close the database, releasing any open file descriptor.

These functions need not be thread-safe.

RETURN VALUE

Upon successful completion, getnetbyaddr(), getnetbyname(), and getnetent() shall return a pointer to a netent structure if the requested entry was found, and a null pointer if the end of the database was reached or the requested entry was not found. Otherwise, a null pointer shall be returned.

The application shall not modify the structure to which the return value points, nor any storage areas pointed to by pointers within the structure. The returned pointer, and pointers within the structure, might be invalidated or the structure or the storage areas might be overwritten by a subsequent call to getnetbyaddr(), getnetbyname(), or getnetent(). The returned pointer, and pointers within the structure, might also be invalidated if the calling thread is terminated.

ERRORS

The getnetbyaddr(), getnetbyname(), getnetent(), and setnetent() functions may fail if:

[EMFILE]

All file descriptors available to the process are currently open.

[ENFILE]

The maximum allowable number of files is currently open in the system.

EXAMPLES

None.

APPLICATION USAGE

None.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

XBD <fcntl.h>, <netdb.h>

CHANGE HISTORY

First released in Issue 6. Derived from the XNS, Issue 5.2 specification.

Issue 7

Austin Group Interpretation 1003.1-2001 #156 is applied.

POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0083 [75] and XSH/TC1-2008/0084 [75] are applied.

POSIX.1-2008, Technical Corrigendum 2, XSH/TC2-2008/0090 [656] is applied.

Issue 8

Austin Group Defect 368 is applied, adding a requirement for FD_CLOEXEC to be set if a file descriptor is used, and adding the [EMFILE] and [ENFILE] errors.