NAME

endhostent, gethostent, sethostent — network host database functions

SYNOPSIS

#include <netdb.h>

void endhostent(void);
struct hostent *gethostent(void);
void sethostent(int stayopen);


DESCRIPTION

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

Note:

In many cases this database is implemented by the Domain Name System, as documented in RFC 1034, RFC 1035, and RFC 3596.

The sethostent() function shall open a connection to the database and set the next entry for retrieval to the first entry in the database. If the stayopen argument is non-zero, the connection shall not be closed by a call to gethostent(), and the implementation may maintain an open file descriptor. If a file descriptor is opened, the FD_CLOEXEC flag shall be set; see <fcntl.h> .

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

Entries shall be returned in hostent structures.

The endhostent() function shall close the connection to the database, releasing any open file descriptor.

These functions need not be thread-safe.

RETURN VALUE

Upon successful completion, the gethostent() function shall return a pointer to a hostent 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.

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 gethostent(). The returned pointer, and pointers within the structure, might also be invalidated if the calling thread is terminated.

ERRORS

The gethostent() and sethostent() 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

endservent

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/TC1-2008/0081 [75,428] and XSH/TC1-2008/0082 [75] are applied.

POSIX.1-2008, Technical Corrigendum 2, XSH/TC2-2008/0089 [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 opened, and adding the [EMFILE] and [ENFILE] errors.

Austin Group Defect 1685 is applied, updating RFC references.