lua(4) - NetBSD Manual Pages

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LUA(4)                  NetBSD Kernel Interfaces Manual                 LUA(4)


NAME

     lua -- control in-kernel Lua states


SYNOPSIS

     lua*

     #include <sys/types.h>
     #include <sys/lua.h>


DESCRIPTION

     The lua device allows to create, control, and delete Lua states in the
     kernel through an ioctl(2) interface.  Moreover, lua can be used to load
     Lua scripts into a Lua state and to assign modules to an existing state,
     i.e. perform the equivalent of the Lua command require.  lua is also used
     to retrieve information about currently active Lua states.


LUA MODULES

     Lua modules are used to provide functionality to Lua scripts not avail-
     able in the language itself, e.g. to access core kernel functionality
     like printing text on the console.  Unlike in user space Lua, where Lua
     modules are files in the filesystem, modules must be provided to lua in
     the form of loadable kernel modules that register their functionality
     with lua.  Modules are loaded using the require Lua command; whether this
     command is available or not is controlled by a sysctl(8) variable.  lua
     by default tries to load a kernel module named luafoo.kmod when it
     encounters the Lua command require 'foo'.


SYSCTL VARIABLES

     The operation of lua can be controlled by means of the following
     sysctl(8) variables:

     kern.lua.autoload
           When set to 1, lua tries to autoload kernel modules.

           The default value is 1.

     kern.lua.bytecode
           When set to 1, loading of Lua bytecode is allowed.

           The default value is 0.

     kern.lua.maxcount
           When set to a value > 0, lua limits the number of instructions exe-
           cuted to this number.

           The default value is 0.

     kern.lua.require
           When set to 1, enables the require command in Lua.

           The default value is 1.

     kern.lua.verbose
           When set to a value > 0, verbosity is increased.

           The default value is 0.


IOCTL INTERFACE

     The following structures and constants are defined in the <sys/lua.h>
     header file:

     LUAINFO(struct lua_info)
           Returns information about the lua states in the lua_info structure:

           #define MAX_LUA_NAME            16
           #define MAX_LUA_DESC            64

           struct lua_state_info {
                   char    name[MAX_LUA_NAME];
                   char    desc[MAX_LUA_DESC];
                   bool    user;
           };

           struct lua_info {
                   int num_states;         /* total number of Lua states */
                   struct lua_state_info *states;
           };

     LUACREATE(struct lua_create)
           Create a new named Lua state with name and description in the
           lua_create structure:

           struct lua_create {
                   char    name[MAX_LUA_NAME];
                   char    desc[MAX_LUA_DESC];
           };

     LUADESTROY(struct lua_create)
           Destroy a named Lua state.

     LUAREQUIRE(struct lua_require)
           Perform the equivalent of the Lua command require in a named state.
           The name of the state and of the module name is passed in the
           lua_require structure:

           #define LUA_MAX_MODNAME         32

           struct lua_require {
                   char    state[MAX_LUA_NAME];
                   char    module[LUA_MAX_MODNAME];
           };

     LUALOAD(struct lua_load)
           Load Lua code from the filesystem into a named Lua state.  The name
           of the state and the path to the Lua code are passed in the
           lua_load structure:

           struct lua_load {
                   char    state[MAX_LUA_NAME];
                   char    path[MAXPATHLEN];
           };

           The path element of the lua_load structure must contain at least
           one `/' character.


FILES

     /dev/lua  Lua device file.


SEE ALSO

     ioctl(2), luactl(8)


HISTORY

     The lua device first appeared in NetBSD 7.0.


AUTHORS

     The lua driver was written by Marc Balmer <mbalmer@NetBSD.org>.


CAVEATS

     The lua device is experimental.  Incompatible changes might be made in
     the future.

NetBSD 9.4                       July 25, 2014                      NetBSD 9.4