Re: io.popen() equivalent in nixio?

[Sean Conner <sean@...>]

It was thus said that the Great Jorge once stated:
> With vanilla Lua I can do
> 
> 	local f = io.popen('cat /proc/cpuinfo') -- runs command
> 	local l = f:read("*a") -- read output of command
> 	f:close()
> 
> How do I get the output of a external program under nixio? It will be a
> long running process, so i'll have to feed the filehandle to nixio.poll,
> create an iterator, etc.
> 
> It will be under Linux, if that helps. I suppose I could do a
> nixio.fork() followed by a nixio.execp(), but that gives me only the
> pid... Where is the stdout for it?

  stdin, stdout and stderr (in fact, all open files) are inhereted by the
child process, so what ever is currently stdin and stdout will be the same
with the child process.  You'll also need to check nixio.pipe() and
nixio.dup().  Something like (untested, since I don't use nixio, but it
should be along these lines; you'll need to add appropriate error checking,
etc):

	read,write = nixio.pipe()
	child = nixio.fork()
	
	if child == 0 then	-- child process
	  nixio.dup(0,read)	-- set stdin of child to read end of pipe
	  nixio.dup(1,write)	-- set stdout of child to write end of pipe
	  nixio.exece('/bin/cat',{ '/proc/cpuinfo'} , nil )
	  -- if we get here, there's an error
	else	-- parent process
	  -- here we can read and write to the vars read,write and
	  -- which sends and receives data to/from the child process
	end

Under Unix (so far, every Unix system I've used for the past twenty years)
have had file descriptor 0 as stdin, 1 as stdout and 2 for stderr.  

  -spc (Hope this helps some)