Module global
Lua global variables.
The basic library provides some core functions to Lua. All the preloaded module of Lua are declared here.
Global(s)
| _G |
A global variable (not a function) that holds the global environment
(that is, |
| _VERSION |
A global variable (not a function) that holds a string containing the current interpreter version. |
| assert(v, message) |
Issues an error when the value of its argument |
| collectgarbage(opt, arg) |
This function is a generic interface to the garbage collector. |
| coroutine |
This library provides generic functions for coroutine manipulation. |
| debug |
The Debug Library. |
| dofile(filename) |
Opens the named file and executes its contents as a Lua chunk. |
| error(message, level) |
Terminates the last protected function called and returns |
| getfenv(f) |
Returns the current environment in use by the function. |
| getmetatable(object) |
If |
| io |
The I/O library provides function for file manipulation. |
| ipairs(t) |
Use to iterate over a table by index. |
| load(func, chunkname) |
Loads a chunk using function |
| loadfile(filename) |
Similar to |
| loadstring(string, chunkname) |
Similar to |
| math |
This library is an interface to the standard C math library. |
| next(table, index) |
Allows a program to traverse all fields of a table. |
| os |
Operating System Facilities. |
| package |
The package library provides basic facilities for loading and building modules in Lua. |
| pairs(t) |
Use to iterate over a table. |
| pcall(f, ...) |
Calls function |
| print(...) |
Receives any number of arguments, and prints their values to |
| rawequal(v1, v2) |
Checks whether |
| rawget(table, index) |
Gets the real value of |
| rawset(table, index, value) |
Sets the real value of |
| require(modname) |
Loads the given module. |
| select(index, ...) |
If |
| setfenv(f, table) |
Sets the environment to be used by the given function. |
| setmetatable(table, metatable) |
Sets the metatable for the given table. |
| string |
This library provides generic functions for string manipulation. |
| table |
This library provides generic functions for table manipulation. |
| tonumber(e, base) |
Tries to convert its argument to a number. |
| tostring(e) |
Receives an argument of any type and converts it to a string in a reasonable format. |
| unpack(list, i, j) |
Returns the elements from the given table. |
| xpcall(f, err) |
This function is similar to |
Global(s)
- #table _G
-
A global variable (not a function) that holds the global environment (that is,
_G._G = _G).Lua itself does not use this variable; changing its value does not affect any environment, nor vice-versa. (Use
setfenvto change environments.)
- #string _VERSION
-
A global variable (not a function) that holds a string containing the current interpreter version.
The current contents of this variable is "
Lua 5.1".
- assert(v, message)
-
Issues an error when the value of its argument
vis false (i.e., nil or false); otherwise, returns all its arguments.messageis an error message; when absent, it defaults to "assertion failed!".Parameters
-
v: if this argument is false an error is issued. -
#string message: an error message. defaults value is "assertion failed".
Return value
All its arguments.
-
- collectgarbage(opt, arg)
-
This function is a generic interface to the garbage collector.
It performs different functions according to its first argument,
opt:- "stop": stops the garbage collector.
- "restart": restarts the garbage collector.
- "collect": performs a full garbage-collection cycle.
- "count": returns the total memory in use by Lua (in Kbytes).
- "step": performs a garbage-collection step. The step "size" is controlled
by
arg(larger values mean more steps) in a non-specified way. If you want to control the step size you must experimentally tune the value ofarg. Returns true if the step finished a collection cycle. - "setpause": sets
argas the new value for the pause of the collector. Returns the previous value for pause. - "setstepmul": sets
argas the new value for the step multiplier of the collector. Returns the previous value for step.
Parameters
-
#string opt: the command to send. -
arg: the argument of the command. (optional)
- coroutine#coroutine coroutine
-
This library provides generic functions for coroutine manipulation.
This is a global variable which hold the preloaded coroutine module.
- debug#debug debug
-
The Debug Library.
This is a global variable which hold the preloaded debug module.
- dofile(filename)
-
Opens the named file and executes its contents as a Lua chunk.
When called without arguments,
dofileexecutes the contents of the standard input (stdin). Returns all values returned by the chunk. In case of errors,dofilepropagates the error to its caller (that is,dofiledoes not run in protected mode).Parameter
-
#string filename: the path to the file. (optional)
-
- error(message, level)
-
Terminates the last protected function called and returns
messageas the error message.Function
errornever returns.Usually,
erroradds some information about the error position at the beginning of the message. Thelevelargument specifies how to get the error position. With level 1 (the default), the error position is where theerrorfunction was called. Level 2 points the error to where the function that callederrorwas called; and so on. Passing a level 0 avoids the addition of error position information to the message.Parameters
-
#string message: an error message. -
#number level: specifies how to get the error position, default value is1.
-
- getfenv(f)
-
Returns the current environment in use by the function.
Parameter
-
f: can be a Lua function or a number that specifies the function at that stack level: Level 1 is the function callinggetfenv. If the given function is not a Lua function, or iffis0,getfenvreturns the global environment. The default forfis1.
-
- getmetatable(object)
-
If
objectdoes not have a metatable, returns nil.Otherwise, if the object's metatable has a
"__metatable"field, returns the associated value. Otherwise, returns the metatable of the given object.Parameter
-
object:
Return value
#table: the metatable of object.
-
- io#io io
-
The I/O library provides function for file manipulation.
This is a global variable which hold the preloaded io module.
- ipairs(t)
-
Use to iterate over a table by index.
Returns three values: an iterator function, the table
t, and 0, so that the construction :for i,v in ipairs(t) do *body* endwill iterate over the pairs (
1,t[1]), (2,t[2]), ..., up to the first integer key absent from the table.Parameter
-
#table t: a table by index.
-
- load(func, chunkname)
-
Loads a chunk using function
functo get its pieces.Each call to
funcmust return a string that concatenates with previous results. A return of an empty string, nil, or no value signals the end of the chunk.If there are no errors, returns the compiled chunk as a function; otherwise, returns nil plus the error message. The environment of the returned function is the global environment.
chunknameis used as the chunk name for error messages and debug information. When absent, it defaults to "=(load)".Parameters
-
func: function which loads the chunk. -
#string chunkname: chunk name used for error messages and debug information, default value is "=(load)".
-
- loadfile(filename)
-
Similar to
load, but gets the chunk from filefilenameor from the standard input, if no file name is given.Parameter
-
#string filename: the path to the file. (optional)
-
- loadstring(string, chunkname)
-
Similar to
load, but gets the chunk from the given string.To load and run a given string, use the idiom
assert(loadstring(s))()When absent,
chunknamedefaults to the given string.Parameters
-
#string string: lua code to load. -
#string chunkname: chunk name used for error messages and debug information, default value is the given string.
-
- math#math math
-
This library is an interface to the standard C math library.
This is a global variable which hold the preloaded math module.
- next(table, index)
-
Allows a program to traverse all fields of a table.
Its first argument is a table and its second argument is an index in this table.
nextreturns the next index of the table and its associated value.When called with nil as its second argument,
nextreturns an initial index and its associated value. When called with the last index, or with nil in an empty table,nextreturns nil.If the second argument is absent, then it is interpreted as nil. In particular, you can use
next(t)to check whether a table is empty. The order in which the indices are enumerated is not specified, even for numeric indices. (To traverse a table in numeric order, use a numerical for or theipairsfunction.)The behavior of
nextis undefined if, during the traversal, you assign any value to a non-existent field in the table. You may however modify existing fields. In particular, you may clear existing fields.Parameters
-
#table table: table to traverse. -
index: initial index.
-
- package#package package
-
The package library provides basic facilities for loading and building modules in Lua.
This is a global variable which hold the preloaded package module.
- pairs(t)
-
Use to iterate over a table.
Returns three values: the
nextfunction, the tablet, and nil, so that the construction :for k,v in pairs(t) do *body* endwill iterate over all key-value pairs of table
t.See function
nextfor the caveats of modifying the table during its traversal.Parameter
-
#table t: table to traverse.
-
- pcall(f, ...)
-
Calls function
fwith the given arguments in protected mode.This means that any error inside
fis not propagated; instead,pcallcatches the error and returns a status code. Its first result is the status code (a boolean), which is true if the call succeeds without errors. In such case,pcallalso returns all results from the call, after this first result. In case of any error,pcallreturns false plus the error message.Parameters
-
f: function to be call in protected mode. -
...: function arguments.
Return values
-
#boolean: true plus the result of
ffunction if its call succeeds without errors. -
#boolean, #string: false plus the error message in case of any error.
-
- print(...)
-
Receives any number of arguments, and prints their values to
stdout, using thetostringfunction to convert them to strings.printis not intended for formatted output, but only as a quick way to show a value, typically for debugging. For formatted output, usestring.format.Parameter
-
...: values to print tostdout.
-
- rawequal(v1, v2)
-
Checks whether
v1is equal tov2, without invoking any metamethod.Returns a boolean.
Parameters
-
v1: -
v2:
Return value
#boolean: true if
v1is equal tov2. -
- rawget(table, index)
-
Gets the real value of
table[index], without invoking any metamethod.tablemust be a table;indexmay be any value.Parameters
-
#table table: -
index: may be any value.
Return value
The real value of
table[index], without invoking any metamethod. -
- rawset(table, index, value)
-
Sets the real value of
table[index]tovalue, without invoking any metamethod.tablemust be a table,indexany value different from nil, andvalueany Lua value. This function returnstable.Parameters
-
#table table: -
index: any value different from nil. -
value: any Lua value.
-
- require(modname)
-
Loads the given module.
The function starts by looking into the
package.loadedtable to determine whethermodnameis already loaded. If it is, thenrequirereturns the value stored atpackage.loaded[modname]. Otherwise, it tries to find a loader for the module.To find a loader,
requireis guided by thepackage.loadersarray. By changing this array, we can change howrequirelooks for a module. The following explanation is based on the default configuration forpackage.loaders.First
requirequeriespackage.preload[modname]. If it has a value, this value (which should be a function) is the loader. Otherwiserequiresearches for a Lua loader using the path stored inpackage.path. If that also fails, it searches for a C loader using the path stored inpackage.cpath. If that also fails, it tries an all-in-one loader (seepackage.loaders).Once a loader is found,
requirecalls the loader with a single argument,modname. If the loader returns any value,requireassigns the returned value topackage.loaded[modname]. If the loader returns no value and has not assigned any value topackage.loaded[modname], thenrequireassigns true to this entry. In any case,requirereturns the final value ofpackage.loaded[modname].If there is any error loading or running the module, or if it cannot find any loader for the module, then
requiresignals an error.Parameter
-
#string modname: name of module to load.
-
- select(index, ...)
-
If
indexis a number, returns all arguments after argument numberindex.Otherwise,
indexmust be the string"#", andselectreturns the total number of extra arguments it received.Parameters
-
index: a number or the string"#" -
...:
-
- setfenv(f, table)
-
Sets the environment to be used by the given function.
fcan be a Lua function or a number that specifies the function at that stack level: Level 1 is the function callingsetfenv.setfenvreturns the given function. As a special case, whenfis 0setfenvchanges the environment of the running thread. In this case,setfenvreturns no values.Parameters
-
f: a Lua function or a number that specifies the stack level. -
#table table: used as environment forf.
Return value
The given function.
-
- setmetatable(table, metatable)
-
Sets the metatable for the given table.
(You cannot change the metatable of other types from Lua, only from C.) If
metatableis nil, removes the metatable of the given table. If the original metatable has a"__metatable"field, raises an error. This function returnstable.Parameters
-
#table table: -
#table metatable:
Return value
The first argument
table. -
- string#string string
-
This library provides generic functions for string manipulation.
This is a global variable which hold the preloaded string module.
- table#table table
-
This library provides generic functions for table manipulation.
This is a global variable which hold the preloaded table module.
- tonumber(e, base)
-
Tries to convert its argument to a number.
If the argument is already a number or a string convertible to a number, then
tonumberreturns this number; otherwise, it returns nil.An optional argument specifies the base to interpret the numeral. The base may be any integer between 2 and 36, inclusive. In bases above 10, the letter '
A' (in either upper or lower case) represents 10, 'B' represents 11, and so forth, with 'Z' representing 35. In base 10 (the default), the number can have a decimal part, as well as an optional exponent part. In other bases, only unsigned integers are accepted.Parameters
-
e: a number or string to convert to a number. -
#number base: the base to interpret the numeral, any integer between 2 and 36.(default is 10).
Return value
#number: a number if conversion succeeds else nil.
-
- tostring(e)
-
Receives an argument of any type and converts it to a string in a reasonable format.
For complete control of how numbers are converted, use
string.format.If the metatable of
ehas a"__tostring"field, thentostringcalls the corresponding value witheas argument, and uses the result of the call as its result.Parameter
-
e: an argument of any type.
Return value
#string: a string in a reasonable format.
-
- unpack(list, i, j)
-
Returns the elements from the given table.
This function is equivalent to
return list[i], list[i+1], ..., list[j]except that the above code can be written only for a fixed number of elements. By default,
iis 1 andjis the length of the list, as defined by the length operator.Parameters
-
#table list: a table by index -
i: index of first value. -
j: index of last value.
-
- xpcall(f, err)
-
This function is similar to
pcall, except that you can set a new error handler.xpcallcalls functionfin protected mode, usingerras the error handler. Any error insidefis not propagated; instead,xpcallcatches the error, calls theerrfunction with the original error object, and returns a status code. Its first result is the status code (a boolean), which is true if the call succeeds without errors. In this case,xpcallalso returns all results from the call, after this first result. In case of any error,xpcallreturns false plus the result fromerr.Parameters
-
f: function to be call in protected mode. -
err: function used as error handler.
Return values
-
#boolean: true plus the result of
ffunction if its call succeeds without errors. -
#boolean, #string: false plus the result of
errfunction.
-