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DBM(3) Library Functions Manual DBM(3)

dbm_clearerr, dbm_close, dbm_delete, dbm_dirfno, dbm_error, dbm_fetch, dbm_firstkey, dbm_nextkey, dbm_open, dbm_storedatabase access functions

library “libc”

#include <fcntl.h>
#include <ndbm.h>

DBM *
dbm_open(const char *base, int flags, mode_t mode);

void
dbm_close(DBM *db);

int
dbm_store(DBM *db, datum key, datum data, int flags);

datum
dbm_fetch(DBM *db, datum key);

int
dbm_delete(DBM *db, datum key);

datum
dbm_firstkey(DBM *db);

datum
dbm_nextkey(DBM *db);

int
dbm_error(DBM *db);

int
dbm_clearerr(DBM *db);

int
dbm_dirfno(DBM *db);

Database access functions. These functions are implemented using dbopen(3) with a hash(3) database.

datum is declared in <ndbm.h>:

typedef struct {
	char *dptr;
	int dsize;
} datum;

The (base, flags, mode) function opens or creates a database. The base argument is the basename of the file containing the database; the actual database has a .db suffix. I.e., if base is "/home/me/mystuff" then the actual database is in the file /home/me/mystuff.db. The flags and mode arguments are passed to open(2). (O_RDWR | O_CREAT) is a typical value for flags; 0660 is a typical value for mode. O_WRONLY is not allowed in flags. The pointer returned by dbm_open() identifies the database and is the db argument to the other functions. The dbm_open() function returns NULL and sets errno if there were any errors.

The (db) function closes the database.

The (db, key, data, flags) function inserts or replaces an entry in the database. The flags argument is either DBM_INSERT or DBM_REPLACE. If flags is DBM_INSERT and the database already contains an entry for key, that entry is not replaced. Otherwise the entry is replaced or inserted. The dbm_store() function normally returns zero but returns 1 if the entry could not be inserted (because flags is DBM_INSERT, and an entry with key already exists) or returns -1 and sets errno if there were any errors.

The (db, key) function returns NULL or the data corresponding to key.

The (db, key) function deletes the entry for key. The dbm_delete() function normally returns zero but returns 1 if there was no entry with key in the database or returns -1 and sets errno if there were any errors.

The (db) function returns the first key in the database. The (db) function returns subsequent keys. The dbm_firstkey() function must be called before dbm_nextkey(). The order in which keys are returned is unspecified and may appear random. The dbm_nextkey() function returns NULL after all keys have been returned.

The (db) function returns the errno value of the most recent error. The (db) function resets this value to 0 and returns 0.

The (db) function returns the file descriptor to the database.

open(2), dbopen(3), hash(3)

These functions (except dbm_dirfno()) are included in the Version 2 of the Single UNIX Specification (“SUSv2”).

April 16, 2006 DragonFly-5.6.1