Pipes

steve64

I'm not able to get any output from pipes.
I also tried the simple example in the documentation:

local pipe = sys.Pipe('systeminfo | findstr /B /C:"OS Name" /C:"OS Version"')
local output = pipe:read(1000)
print(output)

Samir

It works, but the example might not work on all computers as it depends on the current Windows language configuration.

Try this one :

local pipe = sys.Pipe('cmd.exe /K "time /T"')
local output = pipe:read(1000)
print(output)

The string argument in the Pipe constructor must be the fullpath of an existing executable. For example, you cannot use cmd internal commands like "time" or "dir".

The system PATH is not used to resolve executables names too.

steve64

I tried with a full path but I'm not yet able to run an exe.
My use case here is to start a python interpreter as a pipe.
Example:

local pipe = sys.Pipe('C:\\Users\\<myself>\\AppData\\Local\\Programs\\Python\\Python310\\python.exe')
local output = pipe:read(100)
print(output)

Samir

You are right, your example using the python interpreter don't work.
I am investigating it. Thank you for your feedback on this.

Samir

Ok, I've done some investigations, and it's not LuaRT related. It caused me a lot of headaches !

In fact, Python on Windows will detect if it is executed with stdout, stderr and stdin redirected.
In this case (when using LuaRT Pipe object), the python interpreter don't send anything to stdout, only to stderr.
Except if you set the -i flag when executing the python interpreter.

It's a very strange behaviour if you ask me...

So here is the solution :

-- force python to run in interactive mode even if stdout, stderr and stdin are redirected to pipe
local pipe = sys.Pipe("python.exe -i")
-- python interpreter prints to stderr when its output is redirected to pipe
print(pipe:readerror(500))
-- execute the python command: print('Hello World !')
pipe:write("print('Hello World !')\n")
-- prints the result (here, the result is on stdout because we used the python print  function)
print(pipe:read(500))