Content-type: text/html Man page of dbm

dbm

Section: C Library Functions (3)
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NAME

dbminit, fetch, store, delete, firstkey, nextkey, forder - Database subroutines  

LIBRARY

DBM Library (libdbm.a)  

SYNOPSIS

#include <dbm.h>

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

int dbminit(
    char *file );

datum fetch(
    datum key );

int store(
    datum key,
    datum content );

int delete(
    datum key );

datum firstkey( void );

datum nextkey(
    datum key );

long forder(
    datum key );  

PARAMETERS

Specifies the database file. Specifies the key. Specifies a value associated with the key parameter.  

DESCRIPTION

The dbminit(), fetch(), store(), delete(), firstkey(), nextkey(), and forder() functions maintain key/content pairs in a database. They are obtained with the -ldbm loader option. The dbm library is provided only for backwards compatibility, having been obsoleted by the ndbm functions in libc. See the manual page for ndbm for more information.

The dbminit(), fetch(), store(), delete(), firstkey(), nextkey(), and forder() functions handle very large databases (up to a billion blocks) and access a keyed item in one or two file system accesses. Arbitrary binary data, as well as normal ASCII strings, are allowed.

The database is stored in two files. One file is a directory containing a bit map and has .dir as its suffix. The second file contains all data and has .pag as its suffix.

Before a database can be accessed, it must be opened by the dbminit() function. At the time that dbminit() is called, the file.dir and file.pag files must exist. (An empty database is created by creating zero-length .dir and .pag files.)

Once open, the data stored under a key is accessed by the fetch() function and data is placed under a key by the store() function. A key (and its associated contents) is deleted by the delete() function. A linear pass through all keys in a database may be made by use of the firstkey() and nextkey() functions. The firstkey() function returns the first key in the database. With any key, the nextkey() function returns the next key in the database. The following code traverses the database: for (key = firstkey(); key.dptr != NULL; key = nextkey(key))  

RETURN VALUES

Upon successful completion, the functions that return an int return 0 (zero). Otherwise, a negative number is returned. The functions that return a datum indicate errors with a null (0) dptr .  

RELATED INFORMATION

Functions: ndbm(3) delim off


 

Index

NAME
LIBRARY
SYNOPSIS
PARAMETERS
DESCRIPTION
RETURN VALUES
RELATED INFORMATION

This document was created by man2html, using the manual pages.
Time: 02:40:54 GMT, October 02, 2010