Database -- the class of all database files

Description

A database file is just like a hash table, except both the keys and values have to be strings. In this example we create a database file, store a few entries, remove an entry with remove, close the file, and then remove the file.

i1 : filename = temporaryFileName () | ".dbm"

o1 = /tmp/M2-30740-0/0.dbm

i2 : x = openDatabaseOut filename

o2 = /tmp/M2-30740-0/0.dbm

o2 : Database

i3 : x#"first" = "hi there"

o3 = hi there

i4 : x#"first"

o4 = hi there

i5 : x#"second" = "ho there"

o5 = ho there

i6 : scanKeys(x,print)
second
first

i7 : remove(x,"second")

o7 = ho there

i8 : scanKeys(x,print)
first

i9 : close x

o9 = 0

i10 : removeFile filename

Functions and methods returning a database:

openDatabase(String) -- see openDatabase -- open a database file
openDatabaseOut(String) -- see openDatabaseOut -- open a database file for writing

Methods that use a database:

Database #? String -- see #? -- check existence of value in a list, hash table, database, or string
isOpen(Database) -- see isOpen -- whether a file or database is open
keys(Database) -- see keys -- keys used in a hash table, dictionary, or database
Database # String -- see List # ZZ -- get value from list, hash table, database, dictionary, or string
Manipulator Database -- see Manipulator -- the class of all file manipulators
remove(Database,String) -- see remove -- remove an entry from a mutable hash table, list, or database
scanKeys(Database,Function) -- see scanKeys -- apply a function to each key in a hash table or database

For the programmer

The object Database is a type, with ancestor class Thing.

The source of this document is in Macaulay2Doc/ov_system.m2:1608:0.

Database -- the class of all database files

Description

See also

Functions and methods returning a database:

Methods that use a database:

For the programmer