debug.debugdebug.getfenvdebug.gethookdebug.getinfodebug.getlocaldebug.getmetatabledebug.getregistrydebug.getfenvdebug.sethookdebug.setlocaldebug.setmetatabledebug.setupvaluedebug.traceback
debug - debugging facilities (standard library)
This library provides the functionality of the debug interface to Lua programs. You should exert care when using this library. The functions provided here should be used exclusively for debugging and similar tasks, such as profiling. Please resist the temptation to use them as a usual programming tool: they can be very slow. Moreover, several of its functions violate some assumptions about Lua code (e.g., that variables local to a function cannot be accessed from outside or that userdata metatables cannot be changed by Lua code) and therefore can compromise otherwise secure code.
All functions in this library are provided inside the
debug table. All functions that operate over a thread
have an optional first argument which is the thread to operate over.
The default is always the current thread.
debug.debugdebug.debug ()
Enters an interactive mode with the user, running each string that the
user enters. Using simple commands and other debug facilities, the
user can inspect global and local variables, change their values,
evaluate expressions, and so on. A line containing only the word
cont finishes this function, so that the caller continues
its execution.
Note that commands for debug.debug are not lexically
nested within any function, and so have no direct access to local
variables.
debug.getfenvdebug.getfenv (o)
Returns the environment of object o.
debug.gethookdebug.gethook ([thread])
Returns the current hook settings of the thread, as three values: the current hook function, the current hook mask, and the current hook count (as set by the debug.sethook function).
debug.getinfodebug.getinfo ([thread,] function [, what])
Returns a table with information about a function. You can give the
function directly, or you can give a number as the value of
function, which means the function running at level
function of the call stack of the given thread:
level 0 is the current function (getinfo itself);
level 1 is the function that called getinfo; and so
on. If function is a number larger than the number of
active functions, then getinfo returns nil.
The returned table may contain all the fields returned by
lua_getinfo, with the string what describing which fields to
fill in. The default for what is to get all information available,
except the table of valid lines. If present, the option 'f' adds a
field named func with the function itself. If present, the option
'L' adds a field named activelines with the table of valid
lines.
For instance, the expression debug.getinfo(1,"n").name
returns a name of the current function, if a reasonable name can be
found, and debug.getinfo(print) returns a table with all
available information about the print function.
debug.getlocaldebug.getlocal ([thread,] level, local)
This function returns the name and the value of the local variable
with index local of the function at level
level of the stack. (The first parameter or local
variable has index 1, and so on, until the last active local
variable.) The function returns nil if there is no local
variable with the given index, and raises an error when called with a
level out of range. (You can call debug.getinfo to check
whether the level is valid.)
Variable names starting with '(' (open parentheses)
represent internal variables (loop control variables, temporaries, and
C function locals).
debug.getmetatabledebug.getmetatable (object)
Returns the metatable of the given object
or nil if it does not have a metatable.
debug.getregistrydebug.getregistry ()
Returns the registry table (see sect 3.5).
debug.getupvalue (func, up)
This function returns the name and the value of the upvalue with index
up of the function func. The function
returns nil if there is no upvalue with the given index.
debug.getfenvdebug.setfenv (object, table)
Sets the environment of the given object to the given
table. Returns object.
debug.sethookdebug.sethook ([thread,] hook, mask [, count])
Sets the given function as a hook. The string mask and
the number count describe when the hook will be called.
The string mask may have the following characters, with the given
meaning:
"c": The hook is called every time Lua calls a function; "r": The hook is called every time Lua returns from a function; "l": The hook is called every time Lua enters a new line of code.
With a count different from zero,
the hook is called after every count instructions.
When called without arguments, debug.sethook turns off the
hook.
When the hook is called, its first parameter is a string describing
the event that has triggered its call: "call",
"return" (or "tail return"),
"line", and "count". For line events, the
hook also gets the new line number as its second parameter. Inside a
hook, you can call getinfo with level 2 to get more
information about the running function (level 0 is the
getinfo function, and level 1 is the hook function),
unless the event is "tail return". In this case, Lua is
only simulating the return, and a call to getinfo will
return invalid data.
debug.setlocaldebug.setlocal ([thread,] level, local, value)
This function assigns the value value to the local
variable with index local of the function at level
level of the stack. The function returns nil if
there is no local variable with the given index, and raises an error
when called with a level out of range. (You can call
getinfo to check whether the level is valid.) Otherwise,
it returns the name of the local variable.
debug.setmetatabledebug.setmetatable (object, table)
Sets the metatable for the given object to the given
table (which can be nil).
debug.setupvaluedebug.setupvalue (func, up, value)
This function assigns the value value to the upvalue with index
up of the function func. The function returns nil if there
is no upvalue with the given index. Otherwise, it returns the name of
the upvalue.
debug.tracebackdebug.traceback ([thread,] [message])
Returns a string with a traceback of the call stack. An optional
message string is appended at the beginning of the
traceback. This function is typically used with xpcall
to produce better error messages.
This is Lua version 5.1.1.
Lua is developed at Lua.org, a laboratory of the Department of Computer Science of PUC-Rio (the Pontifical Catholic University of Rio de Janeiro in Brazil). For more information about the authors, see http://www.lua.org/authors.html .
Lua is licensed under the terms of the MIT license reproduced below. This means that Lua is free software and can be used for both academic and commercial purposes at absolutely no cost.
For details and rationale, see http://www.lua.org/license.html .
~~~~~
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~~~~~