MENU

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.

coroutine.wrap()
  • References/Lua/Lua/Standard Libraries/Coroutine Manipulation

coroutine.wrap (f) Creates a new coroutine, with body f. f must be a function. Returns a function that resumes the coroutine each time it is called.

2025-01-10 15:47:30
coroutine.yield()
  • References/Lua/Lua/Standard Libraries/Coroutine Manipulation

coroutine.yield (···) Suspends the execution of the calling coroutine. Any arguments to yield are passed as extra results to resume.

2025-01-10 15:47:30
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

2025-01-10 15:47:30
debug.getmetatable()
  • References/Lua/Lua/Standard Libraries/The Debug Library

debug.getmetatable (value) Returns the metatable of the given value or nil if it does not have a metatable.

2025-01-10 15:47:30
string.gmatch()
  • References/Lua/Lua/Standard Libraries/String Manipulation

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

2025-01-10 15:47:30
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

2025-01-10 15:47:30
io.type()
  • References/Lua/Lua/Standard Libraries/Input and Output Facilities

io.type (obj) Checks whether obj is a valid file handle. Returns the string "file" if obj is an open file handle, "closed file"

2025-01-10 15:47:30
print()
  • References/Lua/Lua/Standard Libraries/Basic Functions

print (···)stdouttostringprint

2025-01-10 15:47:30
tonumber()
  • References/Lua/Lua/Standard Libraries/Basic Functions

tonumber (e [, base]) When called with no base, tonumber tries to convert its argument to a number. If the argument is already a number or a string convertible

2025-01-10 15:47:30
utf8.codepoint()
  • References/Lua/Lua/Standard Libraries/UTF-8 Support

utf8.codepoint (s [, i [, j]])sijiji

2025-01-10 15:47:30