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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.

debug.traceback()
  • References/Lua/Lua/Standard Libraries/The Debug Library

debug.traceback ([thread,] [message [, level]]) If message is present but is neither a string nor nil, this function returns message without further

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

string.upper (s)

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

dofile ([filename])dofilestdindofiledofile

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package.searchpath()
  • References/Lua/Lua/Standard Libraries/Modules

package.searchpath (name, path [, sep [, rep]]) Searches for the given name in the given path. A path is a string containing a sequence of templates

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debug.upvaluejoin()
  • References/Lua/Lua/Standard Libraries/The Debug Library

debug.upvaluejoin (f1, n1, f2, n2) Make the n1-th upvalue of the Lua closure f1 refer to the n2-th upvalue of the Lua closure f2

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utf8.char()
  • References/Lua/Lua/Standard Libraries/UTF-8 Support

utf8.char (···)

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

rawget (table, index)table[index]__indextableindex

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debug.getregistry()
  • References/Lua/Lua/Standard Libraries/The Debug Library

debug.getregistry () Returns the registry table (see §4.5).

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file:seek()
  • References/Lua/Lua/Standard Libraries/Input and Output Facilities

file:seek ([whence [, offset]]) Sets and gets the file position, measured from the beginning of the file, to the position given by offset plus a base specified by

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