Embedding Lua in 5 Minutes

So at the UKUUG Spring Conference I kind of decided that there weren’t enough different dynamic languages being talked about; in fact it was pretty much divided into Python land and Perl land (at least as far as dynamic languages were concerned). So I decided to give a 5 minute lightning talk at the end of the conference, on embedding Lua into an application in 5 minutes.

This was my first lightning talk and it was a bit scary and a lot of fun. I highly recommend the experience.

I decided that instead of talking about embedding Lua, I would actually do it, standing in front of the conference live. Including downloading the Lua sources and compiling them (yay for working conference wifi). I thought this was hilarious, I have no idea what anyone else thought. I surprised myself by being able to type code in vi and talk at the same time, though I’m not sure I made much sense.

Here’s an example using the new command line option I added to yes:

$ ./a.out -l 'x=x or 1; x=x*2; return x' | head
2
4
8
16
32
64
128
256
512
1024

For the sake of completeness here is the modified version of yes.c that I ended up with:

#include <sys/cdefs.h>

#include <stdio.h>
#include "lua.h"
#include "lauxlib.h"

int main __P((int, char **));

int
main(argc, argv)
        int argc;
        char **argv;
{
  if(argc >= 3 && strcmp(argv[2], "-l")) {
    lua_State *l = luaL_newstate();
    luaL_openlibs(l);

    while(1) {
      luaL_dostring(l, argv[2]);
      puts(lua_tostring(l, -1));
      lua_settop(l, 0);
    }
  }

        if (argc > 1)
                for(;;)
                        (void)puts(argv[1]);
        else for (;;)
                (void)puts("y");
}

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