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DBM(3X) DBM(3X) NAME dbminit, fetch, store, delete, firstkey, nextkey - database subroutines SYNOPSIS dbminit(file) char *file; datum fetch(key) datum key; store(key, value) datum key, value; delete(key) datum key; datum firstkey() datum nextkey(key) datum key; DESCRIPTION These functions maintain key/value pairs (each pair is a datum) in a data base. The functions will handle very large databases in one or two file system accesses per key. The functions are loaded with ld(1) option -ldbm. A datum is defined as typedef struct { char *dptr; int dsize; } datum; A datum object specifies a string of dsize bytes pointed to by dptr. Arbitrary binary data, as well as normal ASCII strings, are allowed. The data base is stored in two files. One file is a directory contain- ing a bit map and has as its suffix. The second file contains all data and has as its suffix. Before a database can be accessed, it must be opened by dbminit. At the time of this call, the files file.dir and file.pag must exist. (An empty database has empty and files.) The value associated with a key is retrieved by fetch and assigned by store. A key and its associated value are deleted by delete. A linear pass through all keys in a database may be made, in random order, by use of firstkey and nextkey. Firstkey will return the first key in the database. With any key nextkey will return the next key in the data- base. This code will traverse the data base: for(key = firstkey(); key.dptr != NULL; key = nextkey(key)) SEE ALSO cbt(3) DIAGNOSTICS All functions that return integers indicate errors with negative val- ues. A zero return indicates success. Routines that return a datum indicate errors with zero dptr. BUGS The file contains holes; its apparent size is about four times its ac- tual content. These files cannot be copied by normal means (cat(1), tar(1), cpio(1), ar(1)) without filling in the holes. Pointers returned by these subroutines refer to static data that is changed by subsequent calls. The sum of the sizes of a key/value pair must not exceed a fixed inter- nal block size. Moreover all key/value pairs that hash together must fit on a single block. Store will return an error in the event that a disk block fills with inseparable data. Delete does not physically reclaim file space, although it does make it available for reuse. DBM(3X)