Using xterm to open a new console: How to while the current console is printing, to print on the new console also.

Question

I'm using python right now. I have a thread that represents my entire program. I want to open another console window using os.system(xterm&) as a thread which works. The only thing is, is it possible to print to the new window while the other thread is printing to the older window?

import sys




import os

def my_fork():
    child_pid = os.fork()
    if child_pid == 0:

        function=open('SMITH747.txt','r')
        f=function.readlines()
        fd = open("output", "w")
        # Open xterm window with logs from that file
        p = subprocess.Popen(["xterm", "-e", "tail", "-f", "output"])
        # Do logging


        while(True):
            for i in range(1):
                fd.write("Hello, world!")
                time.sleep(2)

            if f==[]:
                pass
            else:
                bud=False

            fd.flush()

    else:
        function=open('SMITH747.txt','w')
        var=input('Enter ')
        if var=='q':
            function.write('yo')

if __name__ == "__main__":
    my_fork()

this is what I have right now: It works except I can't get it to read my file and terminate if f is not []. I would appreciate it so much if someone can help me debug this part. Then it will be perfect!

Answer 1

You could probably create a named pipe, have your new thread write to that, then spawn a new terminal that runs tail -f on the pipe.

Answer 2

Use subprocess.Popen() for creation of the children process. In that case you can specify PIPE and write to stdin of the children.

import subprocess
p = subprocess.Popen(["xterm"], stdin=subprocess.PIPE, stdout=subprocess.PIPE)
output = p.communicate("inputmessage")[0]

Update:

Directly xterm does not received input, so here is not so direct way.

import subprocess
# Open file for output
fd = open("output", "w")
# Open xterm window with logs from that file
p = subprocess.Popen(["xterm", "-e", "tail", "-f", "output"])
# Do logging
fd.write("Hello, world!")
fd.flush()

Now you can redirect stdout descriptor to the fd, so the "print" will write output to the file. But it will be for all threads...

Answer 3

For a unix solution:

The command tee is meant to allow output to a log file while still outputing to the console. You second term can just follow that file with tail -f on the output file.

Answer 4

the reason why I want to open a new console is so that I can var=input('Enter q here: ') >in new window and wait for user to press enter thus terminating the old thread...

Simplest way i see, is helper script for asking user in separate terminal. And it is not stdin/stdout redirection hacks :)

main.py:

import os
os.mkfifo("/tmp/1234");
os.system("xterm -e python input.py &")
f = open("/tmp/1234")
print(f.read())

input.py:

var=input('Enter q here: ')
fifo = open('/tmp/1234','w')
fifo.write(str(var))
fifo.flush()

Answer 5

import os, subprocess, time, threading

# Reads commands from fifo in separate thread.
# if kill command is received, then down continue flag.
class Killer(threading.Thread):
   def __init__ (self):
        threading.Thread.__init__(self)
        self.continueFlag = True
   def run(self):
        fd=open('ipc','r')
        command = fd.read()
        if command == "kill\n":
            self.continueFlag = False

def my_fork():

    # create fifo for reliable inter-process communications
    # TODO: check existence of fifo
    os.mkfifo('ipc')

    # Be careful with threads and fork
    child_pid = os.fork()
    if child_pid == 0:

        fd = open("output", "w")
        subprocess.Popen(["xterm", "-e", "tail", "-f", "output"])

        # Create and start killer, be careful with threads and fork
        killer = Killer()
        killer.start()

        # Perform work while continue flag is up
        while(killer.continueFlag):
            fd.write("Hello, world!\n")
            fd.flush()
            time.sleep(2)

        # need to kill subprocess with opened xterm

    else:
        # File must be fifo, otherwise race condition is possible.
        fd=open('ipc','w')
        var=input('Enter ')
        if var=='q':
            fd.write('kill\n')

if __name__ == "__main__":
    my_fork()

P.S. discussion is far away from topic, probably you should change it.