Standard Libraries

Standard Libraries:

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.

Links:

https://www.lua.org/manual/5.3/manual.html#6

io.read()

References/Lua/Lua/Standard Libraries/Input and Output Facilities

io.read (···) Equivalent to io.input():read(···).

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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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Patterns

References/Lua/Lua/Standard Libraries/String Manipulation

6.4.1 – Patterns Patterns in Lua are described by regular strings, which are interpreted as patterns by the pattern-matching functions

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debug.getuservalue()

References/Lua/Lua/Standard Libraries/The Debug Library

debug.getuservalue (u) Returns the Lua value associated to u. If u is not a full userdata, returns nil.

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utf8.len()

References/Lua/Lua/Standard Libraries/UTF-8 Support

utf8.len (s [, i [, j]])sijij

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os.setlocale()

References/Lua/Lua/Standard Libraries/Operating System Facilities

os.setlocale (locale [, category]) Sets the current locale of the program. locale is a system-dependent string specifying a locale; category is an optional

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getmetatable()