6 – Standard Libraries

The standard Lua libraries provide useful functions that are implemented directly through the C API. Some of these functions provide essential services to the language (e.g., type and getmetatable); others provide access to "outside" services (e.g., I/O); and others could be implemented in Lua itself, but are quite useful or have critical performance requirements that deserve an implementation in C (e.g., table.sort).

All libraries are implemented through the official C API and are provided as separate C modules. Currently, Lua has the following standard libraries:

  • basic library (§6.1);
  • coroutine library (§6.2);
  • package library (§6.3);
  • string manipulation (§6.4);
  • basic UTF-8 support (§6.5);
  • table manipulation (§6.6);
  • mathematical functions (§6.7) (sin, log, etc.);
  • input and output (§6.8);
  • operating system facilities (§6.9);
  • debug facilities (§6.10).

Except for the basic and the package libraries, each library provides all its functions as fields of a global table or as methods of its objects.

To have access to these libraries, the C host program should call the luaL_openlibs function, which opens all standard libraries. Alternatively, the host program can open them individually by using luaL_requiref to call luaopen_base (for the basic library), luaopen_package (for the package library), luaopen_coroutine (for the coroutine library), luaopen_string (for the string library), luaopen_utf8 (for the UTF8 library), luaopen_table (for the table library), luaopen_math (for the mathematical library), luaopen_io (for the I/O library), luaopen_os (for the operating system library), and luaopen_debug (for the debug library). These functions are declared in lualib.h.

math.deg()
  • References/Lua/Lua/Standard Libraries/Mathematical Functions

math.deg (x) Converts the angle x from radians to degrees.

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dofile()
  • References/Lua/Lua/Standard Libraries/Basic Functions

dofile ([filename])dofilestdindofiledofile

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string.gmatch()
  • References/Lua/Lua/Standard Libraries/String Manipulation

string.gmatch (s, pattern)pattern§6.4.1spattern As

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package.cpath
  • References/Lua/Lua/Standard Libraries/Modules

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

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_VERSION
  • References/Lua/Lua/Standard Libraries/Basic Functions

_VERSION A global variable (not a function) that holds a string containing the running Lua version. The current value of this variable is "Lua 5.3".

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pcall()
  • References/Lua/Lua/Standard Libraries/Basic Functions

pcall (f [, arg1, ···]) Calls function f with the given arguments in protected mode. This means that any error inside f is not propagated; instead

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next()
  • References/Lua/Lua/Standard Libraries/Basic Functions

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

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io.flush()
  • References/Lua/Lua/Standard Libraries/Input and Output Facilities

io.flush () Equivalent to io.output():flush().

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string.dump()
  • References/Lua/Lua/Standard Libraries/String Manipulation

string.dump (function [, strip]) Returns a string containing a binary representation (a binary chunk) of the given function, so that a later

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io.popen()
  • References/Lua/Lua/Standard Libraries/Input and Output Facilities

io.popen (prog [, mode]) This function is system dependent and is not available on all platforms. Starts program prog in a separated process and returns

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