lib/luapackage.pir - Lua Package Library


The package library provides basic facilities for loading and building modules in Lua. It exports two of its functions directly in the global environment: require and module. Everything else is exported in a table package.

See "Lua 5.1 Reference Manual", section 5.3 "Modules".

Functions & Variables ^

module (name [, ...])

Creates a module. If there is a table in package.loaded[name], this table is the module. Otherwise, if there is a global table t with the given name, this table is the module. Otherwise creates a new table t and sets it as the value of the global name and the value of package.loaded[name]. This function also initializes t._NAME with the given name, t._M with the module (t itself), and t._PACKAGE with the package name (the full module name minus last component; see below). Finally, module sets t as the new environment of the current function and the new value of package.loaded[name], so that require returns t.

If name is a compound name (that is, one with components separated by dots), module creates (or reuses, if they already exist) tables for each component. For instance, if name is a.b.c, then module stores the module table in field c of field b of global a.

This function may receive optional options after the module name, where each option is a function to be applied over the module.


require (modname)

Loads the given module. The function starts by looking into the table package.loaded to determine whether modname is already loaded. If it is, then require returns the value stored at package.loaded[modname]. Otherwise, it tries to find a loader for the module.

To find a loader, first require queries package.preload[modname]. If it has a value, this value (which should be a function) is the loader. Otherwise require searches for a Lua loader using the path stored in package.path. If that also fails, it searches for a C loader using the path stored in package.cpath. If that also fails, it tries an all-in-one loader (see below).

If there is any error loading or running the module, or if it cannot find any loader for the module, then require signals an error.



The path used by require to search for a C loader.

Lua initializes the C path package.cpath in the same way it initializes the Lua path package.path, using the environment variable LUA_CPATH (plus another default path).



A table used by require to control which modules are already loaded. When you require a module modname and package.loaded[modname] is not false, require simply returns the value stored there.


package.loadlib (libname, funcname)

Dynamically links the host program with the C library libname. Inside this library, looks for a function funcname and returns this function as a C function.

This is a low-level function. It completely bypasses the package and module system. Unlike require, it does not perform any path searching and does not automatically adds extensions. libname must be the complete file name of the C library, including if necessary a path and extension. funcname must be the exact name exported by the C library .



The path used by require to search for a Lua loader.

At start-up, Lua initializes this variable with the value of the environment variable LUA_PATH or with a default path, if the environment variable is not defined. Any ";;" in the value of the environment variable is replaced by the default path.

A path is a sequence of templates separated by semicolons. For each template, require will change each interrogation mark in the template by filename, which is modname with each dot replaced by a "directory separator" (such as "/" in Unix); then it will try to load the resulting file name. So, for instance, if the Lua path is

the search for a Lua loader for module foo will try to load the files ./foo.lua, ./, and /usr/local/foo/init.lua, in that order.



A table to store loaders for specific modules (see require).


package.seeall (module)

Sets a metatable for module with its __index field referring to the global environment, so that this module inherits values from the global environment. To be used as an option to function module.