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DBM (3) | C library functions | Unix Manual Pages | :man

NAME

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

CONTENTS

Synopsis
Description
See Also
Standards

SYNOPSIS


.In fcntl.h
.In 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.


.Vt datum is declared in
.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_close function normally returns zero.

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


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