- #GET DATA RETURN FROM PYTHON SUBPROCESS CALL HOW TO#
- #GET DATA RETURN FROM PYTHON SUBPROCESS CALL CODE#
When executing the command with os.system() we see the output for each ping attempt being printed one at the time, in the same way we would see it in the Linux shell.Įxecution with os.popen > os.popen('ping -c 5 localhost') We will use the ping command with the -c flag to stop the execution of the command after a specific number of ECHO_RESPONSE packets (in this example 5): $ ping -c 5 localhostĮxecution with os.system > os.system('ping -c 5 localhost')
Makes sense? Do OS System and OS Popen Wait for Command Completion?īefore moving to a different way of running shell commands in Python, I want to see the behaviour of os.system() and os.popen() with a command that takes few seconds to complete. We can use the value of output.close() for error handling in our Python scripts. Success scenario > output = os.popen('date')įailure scenario > output = os.popen('daet')
#GET DATA RETURN FROM PYTHON SUBPROCESS CALL CODE#
It provides the return code of the subprocess in case of error. The close method returns None if the command is executed successfully. To do that we can use the close method of the file object returned by os.popen. When executing shell commands in Python it’s important to understand if a command is executed successfully or not. We can use os.popen and the read function in a single line: > import os The result is an empty string because we can only read from the file object once. Have a look at what happens if we use the read method again on the same object: > output.read() The popen function returns an open file object and to read its value you can use the read method: > import os To be able to store the output of a command in a variable you can use the os.popen() function.
You usually run commands, store their output in a variable and then implement some logic in your script that does whatever you need to do with that variable (e.g. And this is one of the most useful things to do when you write a script.
Using os.system() we cannot store the output of the Linux command into a variable. Later on in this article we will make a comparison between os.system and a different Python module called subprocess. I have written another article that explains Bash exit codes if it’s something you would like to know more about. Notice how the exit status is different from the one returned by the Bash shell: $ daet Let’s confirm that, by introducing a spelling mistake in the date command: > os.system('daet') That’s the exit code of the Linux command.Ī successful command in Linux returns a 0 exit code and a non-zero exit code is returned in case of failure. We still see the output of the date command but we also see a 0 in the last line. Let’s see what happens when we run the same code in the Python shell: > import os This is the output of the os.system() function: $ python shell_command.py It uses the system function of the os module to run the Linux date command: import os I have created a simple Python script called shell_command.py.
Print Shell Environment Variables in Python.
#GET DATA RETURN FROM PYTHON SUBPROCESS CALL HOW TO#