Module global
Lua global functions.
Functions
| assert (v, message) | Issues an error when its argument `v` is false. |
| collectgarbage (opt, arg) | This function is a generic interface to the garbage collector. |
| dofile (filename) | Opens the named file and executes its contents as a Lua chunk. |
| error (message, level) | Terminates the last protected function called. |
| getmetatable (object) | If `object` does not have a metatable, returns nil. |
| ipairs (t) | For iterating over sequences. |
| load (ld, source, mode, env) | Loads a chunk. |
| loadfile (filename, mode, env) | Similar to `load`, but gets the chunk from file `filename`. |
| next (table, index) | Allows a program to traverse all fields of a table. |
| pairs (t) | For iterating over all key-value pairs of a table. |
| pcall (f, arg1, ...) | Calls function `f` with the given arguments in *protected mode*. |
| print (...) | Prints any number of values to `stdout`. |
| rawequal (v1, v2) | Checks whether `v1` is equal to `v2`. |
| rawget (table, index) | Gets the real value of `table[index]`. |
| rawset (table, index, value) | Sets the real value of `table[index]` to `value`. |
| select (index, ...) | Returns all arguments after argument number `index`. |
| setmetatable (table, metatable) | Sets the metatable for the given table. |
| tonumber (e, base) | Tries to convert its argument to a number. |
| tostring (e) | Converts any value to a string in a reasonable format. |
| type (v) | Returns the type of its only argument, coded as a string. |
| xpcall (f, err) | This function is similar to `pcall`, except that you can set a new error handler. |
| require (modname) | Loads the given module. |
Tables
| _G | A global variable (not a function) that holds the global environment (that is, `_G._G = _G`). |
| _VERSION | A global variable (not a function) that holds a string containing the current interpreter version. |
Functions
- assert (v, message)
-
Issues an error when its argument `v` is false.
That is, nil or false. otherwise, returns all its arguments.
`message` is an error when absent, it defaults to "assertion failed!"
Parameters:
- v
- message
- 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 of * "arg". Returns true if the step finished a collection cycle. * "setpause": sets `arg` as the new value for the *pause* of the collector (see 2.10). Returns the previous value for *pause*. * "setstepmul": sets `arg` as the new value for the *step multiplier* of the collector (see 2.10). Returns the previous value for *step*.
Parameters:
- opt
- arg
- dofile (filename)
-
Opens the named file and executes its contents as a Lua chunk. When
called without arguments,
`dofile` executes the contents of the standard input (`stdin`). Returns
all values returned by the chunk. In case of errors, `dofile` propagates
the error to its caller (that is, `dofile` does not run in protected mode).
Parameters:
- filename
- error (message, level)
-
Terminates the last protected function called.
Returns `message` as the error message.
Function `error` never returns.
Usually, `error` adds some information about the error position at the
beginning of the message. The `level` argument specifies how to get the
error position. With level 1 (the default), the error position is where the
`error` function was called. Level 2 points the error to where the function
that called `error` was called; and so on. Passing a level 0 avoids the
addition of error position information to the message.
Parameters:
- message
- level
- getmetatable (object)
-
If `object` does 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.
Parameters:
- object
- ipairs (t)
-
For iterating over sequences. Returns three values: an iterator function, the table `t`, and 0,
so that the construction
for i,v in ipairs(t) do *body* end
will iterate over the pairs (`1,t[1]`), (`2,t[2]`), ..., up to the
first integer key absent from the table.
Parameters:
- t
- load (ld, source, mode, env)
-
Loads a chunk.
If `ld` is a string, the chunk is this string.
If `ld` is a function, load calls it repeatedly to get the chunk pieces. Each call to `ld` must 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 syntactic errors, returns the compiled chunk as a function;
otherwise, returns nil plus the error message.
If the resulting function has upvalues, the first upvalue is set to the value of the global environment or to `env`,
if that parameter is given. When loading main chunks, the first upvalue will be the`_ENV` variable (see 2.2).
`source` is used as the source of the chunk for error messages and debug information (see 4.9).
When absent, it defaults to `ld`, if `ld` is a string, or to "=(load)" otherwise.
The string `mode` controls whether the chunk can be text or binary (that is, a precompiled chunk).
It may be the string "b" (only binary chunks), "t" (only text chunks), or "bt" (both binary and text).
The default is "bt"
Parameters:
- ld
- source
- mode
- env
- loadfile (filename, mode, env)
-
Similar to `load`, but gets the chunk from file `filename`. Or from the
standard input, if no file name is given.
Parameters:
- filename
- mode
- env
- 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. `next` returns
the next index of the table and its associated value.
When called with nil as its second argument, `next` returns an initial index and its associated value. When called with the last index, or with nil in an empty table, `next` returns 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 the `ipairs` function.)
The behavior of `next` is *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
- index
- pairs (t)
-
For iterating over all key-value pairs of a table.
Returns three values: the `next` function, the table `t`, and nil,
so that the construction
for k,v in pairs(t) do *body* end
will iterate over all key-value pairs of table `t`.
See function `next` for the caveats of modifying the table during its
traversal.
Parameters:
- t
- pcall (f, arg1, ...)
-
Calls function `f` with the given arguments in *protected mode*. This
means that any error inside `f` is not propagated; instead, `pcall` catches
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,
`pcall` also returns all results from the call, after this first result. In
case of any error, `pcall` returns false plus the error message.
Parameters:
- f
- arg1
- ...
- print (...)
-
Prints any number of values to `stdout`.
Uses the `tostring` function to convert them to strings. `print` is not
intended for formatted output, but only as a quick way to show a value,
typically for debugging. For formatted output, use `string.format`.
Parameters:
- ...
- rawequal (v1, v2)
-
Checks whether `v1` is equal to `v2`. Does not invoke any
metamethod. Returns a boolean.
Parameters:
- v1
- v2
- rawget (table, index)
-
Gets the real value of `table[index]`. Does not invoke any
metamethod. `table` must be a table; `index` may be any value.
Parameters:
- table
- index
- rawset (table, index, value)
-
Sets the real value of `table[index]` to `value`. Does not invoke any
metamethod. `table` must be a table, `index` any value different from nil,
and `value` any Lua value.
This function returns `table`.
Parameters:
- table
- index
- value
- select (index, ...)
-
Returns all arguments after argument number
`index`. Otherwise, `index` must be the string `"#"`, and `select` returns
the total number of extra arguments it received.
Parameters:
- index
- ...
- setmetatable (table, metatable)
-
Sets the metatable for the given table. (You cannot change the metatable
of other types from Lua, only from C.) If `metatable` is nil, removes the
metatable of the given table. If the original metatable has a `"__metatable"`
field, raises an error.
This function returns `table`.
Parameters:
- table
- metatable
- 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 `tonumber` returns 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
(see 2.1). In other bases, only unsigned integers are accepted.
Parameters:
- e
- base
- tostring (e)
-
Converts any value to a string in a reasonable format.
For complete control of how numbers are converted, use `string.format`.
If the metatable of `e` has a `"__tostring"` field, then `tostring` calls
the corresponding value with `e` as argument, and uses the result of the
call as its result.
Parameters:
- e
- type (v)
-
Returns the type of its only argument, coded as a string. The possible
results of this function are "
`nil`" (a string, not the value nil), "`number`", "`string`", "`boolean`",
"`table`", "`function`", "`thread`", and "`userdata`".
Parameters:
- v
- xpcall (f, err)
-
This function is similar to `pcall`, except that you can set a new
error handler.
`xpcall` calls function `f` in protected mode, using `err` as the error
handler. Any error inside `f` is not propagated; instead, `xpcall` catches
the error, calls the `err` function 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, `xpcall`
also returns all results from the call, after this first result. In case
of any error, `xpcall` returns false plus the result from `err`.
Parameters:
- f
- err
- require (modname)
-
Loads the given module. The function starts by looking into the
`package.loaded` table 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, `require` is guided by the `package.loaders` array. By
changing this array, we can change how `require` looks for a module. The
following explanation is based on the default configuration for
`package.loaders`.
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
`package.loaders`).
Once a loader is found, `require` calls the loader with a single argument,
`modname`. If the loader returns any value, `require` assigns the returned
value to `package.loaded[modname]`. If the loader returns no value and
has not assigned any value to `package.loaded[modname]`, then `require`
assigns true to this entry. In any case, `require` returns the final value
of `package.loaded[modname]`.
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.
Parameters:
- modname
Tables
- _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. (Set `__ENV` to change environments in functions)
- _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`".