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.

os.exit()
  • References/Lua/Lua/Standard Libraries/Operating System Facilities

os.exit ([code [, close]]) Calls the ISO C function exit to terminate the host program. If code is true, the returned status is EXIT_SUCCESS;

2025-01-10 15:47:30
os.getenv()
  • References/Lua/Lua/Standard Libraries/Operating System Facilities

os.getenv (varname) Returns the value of the process environment variable varname, or nil if the variable is not defined.

2025-01-10 15:47:30
package.path
  • References/Lua/Lua/Standard Libraries/Modules

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

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

io.input ([file]) When called with a file name, it opens the named file (in text mode), and sets its handle as the default input file. When called with a file handle, it simply

2025-01-10 15:47:30
os.tmpname()
  • References/Lua/Lua/Standard Libraries/Operating System Facilities

os.tmpname () Returns a string with a file name that can be used for a temporary file. The file must be explicitly opened before its use and explicitly removed when no longer

2025-01-10 15:47:30
math.max()
  • References/Lua/Lua/Standard Libraries/Mathematical Functions

math.max (x, ···) Returns the argument with the maximum value, according to the Lua operator <. (integer/float)

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

_G§2.2

2025-01-10 15:47:30
require()
  • References/Lua/Lua/Standard Libraries/Modules

require (modname) Loads the given module. The function starts by looking into the package

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

io.write (···) Equivalent to io.output():write(···).

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

coroutine.status (co) Returns the status of coroutine co, as a string: "running", if the coroutine is running (that is, it called status);

2025-01-10 15:47:30