Re: Check for a keypress
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- Subject: Re: Check for a keypress
- From: Philipp Janda <siffiejoe@...>
- Date: 2013年11月30日 20:36:10 +0100
Am 30.11.2013 13:03 schröbte John Hind:
On 2013年11月29日, Jose Torre-Bueno wrote:
Is there a way from inside Lua to check whether any key has been
pressed? io.read() will get a line from the console but if there
is no input it pends waiting for input. I would like to be able
to write a test that gets input if any is ready but would continue
if there is none. It is not obvious to me if this can be done at
all.
Not a solution, but some background. Here is a a Lua C function to do it extracted from one of my libraries, complete with comment:
/* R1: Boolean, true if there is outstanding data in the keyboard buffer.
** This is a helper to allow a demonstration terminal program implemented on the command line.
** Need a solution for Linux, although _kbhit is POSIX there seem to be theological reasons for not
** having it in Linux and it is not in baseline C.
What made you think that `_kbhit` (or `kbhit`) was in POSIX? IIRC, it's
an old DOS function (and it's not listed here[1]).
*/
static int luakbhit(lua_State* L) {
#if defined(LUA_WIN)
lua_pushboolean(L, _kbhit());
#else
lua_pushboolean(L, FALSE);
#endif
return 1;
}
Search online for "_kbhit" for more background on the theology!
I did, but found nothing on theology. Could you share a link?
@OP: In case you are on a POSIX machine you could use luaposix[2]:
local p = require( "posix" )
local function table_copy( t )
local copy = {}
for k,v in pairs( t ) do
if type( v ) == "table" then
copy[ k ] = table_copy( v )
else
copy[ k ] = v
end
end
return copy
end
assert( p.isatty( p.STDIN_FILENO ), "stdin not a terminal" )
local saved_tcattr = assert( p.tcgetattr( p.STDIN_FILENO ) )
local raw_tcattr = table_copy( saved_tcattr )
raw_tcattr.lflag = bit32.band( raw_tcattr.lflag, bit32.bnot(
p.ICANON ) )
local guard = setmetatable( {}, { __gc = function()
p.tcsetattr( p.STDIN_FILENO, p.TCSANOW, saved_tcattr )
end } )
local function kbhit()
assert( p.tcsetattr( p.STDIN_FILENO, p.TCSANOW, raw_tcattr ) )
local r = assert( p.rpoll( p.STDIN_FILENO, 0 ) )
assert( p.tcsetattr( p.STDIN_FILENO, p.TCSANOW, saved_tcattr ) )
return r > 0
end
---[[
-- Test code
repeat until kbhit()
print( "key pressed!" )
--]]
HTH,
Philipp
[1]: http://pubs.opengroup.org/onlinepubs/9699919799/
[2]: https://github.com/luaposix/luaposix