NAME

dbm_clearerr, dbm_close, dbm_delete, dbm_dirfno, dbm_error, dbm_fetch, dbm_firstkey, dbm_nextkey, dbm_open, dbm_store — database access functions

SYNOPSIS

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

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

DESCRIPTION

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 dbm_open( 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 dbm_close( db) function closes the database.

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

The dbm_delete( 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 dbm_firstkey( db) function returns the first key in the database. The dbm_nextkey( db) function returns subsequent keys. The db_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 dbm_error( db) function returns the errno value of the most recent error. The dbm_clearerr( db) function resets this value to 0 and returns 0.

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

SEE ALSO

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

STANDARDS

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