python os.system seems to hang for no reason

Question

So I am monitoring the modification time of numerous files. When the file is updated, I copy it over ssh to another machine. Here is a SSCCE of what I have:

import os
import time

send = "/home/pi/PythonScripts/tempData.txt"
check = "/home/pi/PythonScripts/check.txt"

statbuf = os.stat(send)
print "Modification time:",statbuf.st_mtime 

def wr2(data):
    file2 = open(check, 'w')
    file2.write(str(data))
    file2.close()
    return 0

def rd():
    file = open(send, 'r')
    line2 = file.readline()
    file.close()
    return line2

def rd2():
    file2 = open(check, 'r')
    line2 = file2.readline()
    file2.close()
    return line2


while(run):
   try:
    statbuf = os.stat(send)
    line2 = rd2()
    print line2

    if (str(statbuf.st_mtime) == line2):
       print "File has not changed...\n"
       time.sleep(1)
    else:
       data = rd()
       print "Data in File: " + data
       os.system("sudo scp /home/pix/PythonScripts/tempData.txt server1:/home/tix/Server1_SSH/Real_Data.txt")
       wr2(statbuf.st_mtime)
       print "New Modification Time:",statbuf.st_mtime 
       time.sleep(1)



   except (KeyboardInterrupt, SystemExit):
        print '\nKeyboard Interrupt Caught!'
        run = 0
        raise

So when it gets to the os.system() command it hangs there not doing anything... however when I run the same exact code on the python interpreter it works just fine. I can't seem to understand what the issue would be... any help would be great!

Answer 1

The sudo is the likely culprit and is probably asking for a password.

Instead of os.system , try using the subprocess module instead. That will let you see the stdout and stderr streams to see what is going on.

Also, I would question the practice of using sudo inside your script. Normally, the decision to use sudo would be left to the person calling the Python script.