How to execute an external command?
The simplest way is os.execute which works like the C system call; it calls out to the shell to execute shell commands and external programs. The return code of the execution is usually zero for success. io.popen calls a command but returns a file object so you can read the output of the command, if the second argument is ‘r’, but you can also pass input to a command with a second argument of ‘w’. Unfortunately, you don’t get a io.popen2, and you don’t get the return code. There are also two serious weaknesses of these two functions when operating in Windows GUI mode; (a) you will get the dreaded black box flashing from os.execute and (b) io.popen just doesn’t work. A way around this is to use COM via LuaCOM. This is part of Lua for Windows LuaCOM allows you to access the Windows Scripting Host (WSH) objects.
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