Return Value of X = Os.System(..)

Return value of x = os.system(..)

os.system() returns the (encoded) process exit value. 0 means success:

On Unix, the return value is the exit status of the process encoded in the format specified for wait(). Note that POSIX does not specify the meaning of the return value of the C system() function, so the return value of the Python function is system-dependent.

The output you see is written to stdout, so your console or terminal, and not returned to the Python caller.

If you wanted to capture stdout, use subprocess.check_output() instead:

x = subprocess.check_output(['whoami'])

What is the return value of os.system() in Python?

The return value of os.system is OS-dependant.

On Unix, the return value is a 16-bit number that contains two different pieces of information. From the documentation:

a 16-bit number, whose low byte is the signal number that killed the process, and whose high byte is the exit status (if the signal number is zero)

So if the signal number (low byte) is 0, it would, in theory, be safe to shift the result by 8 bits (result >> 8) to get the error code. The function os.WEXITSTATUS does exactly this. If the error code is 0, that usually means that the process exited without errors.

On Windows, the documentation specifies that the return value of os.system is shell-dependant. If the shell is cmd.exe (the default one), the value is the return code of the process. Again, 0 would mean that there weren't errors.

For others error codes:

• on Linux
• on Windows

How to store the return value of os.system that it has printed to stdout in python?

import subprocess
p = subprocess.Popen('my_command', stdout=subprocess.PIPE, stderr=subprocess.PIPE)
out, error = p.communicate()

Assign output of os.system to a variable and prevent it from being displayed on the screen

From "Equivalent of Bash Backticks in Python", which I asked a long time ago, what you may want to use is popen:

os.popen('cat /etc/services').read()

From the docs for Python 3.6,

This is implemented using subprocess.Popen; see that class’s
documentation for more powerful ways to manage and communicate with
subprocesses.

---

Here's the corresponding code for subprocess:

import subprocess

proc = subprocess.Popen(["cat", "/etc/services"], stdout=subprocess.PIPE, shell=True)
(out, err) = proc.communicate()
print "program output:", out

How to get the output from os.system()?

Use subprocess:

import subprocess
print(subprocess.check_output(['nslookup', 'google.com']))

If the return code is not zero it will raise a CalledProcessError exception:

try:
    print(subprocess.check_output(['nslookup', 'google.com']))
except subprocess.CalledProcessError as err:
    print(err)

os.system only returns the exit code of the command. Here 0 means success. Any other number stands for an operating-system-dependent error. The output goes to stdout of this process. subprocess intends to replace os.system.

subprocess.check_output is a convenience wrapper around subprocess.Popen that simplifies your use case.

OS.system- adding the output of OS .system output command to the command of another os system command

os.system does not return the output of the command - it returns the errorlevel.

If you need command output, use

wwn = os.popen(var).read()

That will assign the output from command var to wwn.

Be warned - the output is returned completely, with the trailing newline. You might want to strip() it before using it.

How to hide or delete the 0 when call to `os.system` in Python?

What about this?

from subprocess import check_output
user_name = check_output('whoami').strip()
print user_name
#out: userX

What does the 0 stand for at the end of the text which os.system() returns?

os.system returns the exit status of the process you executed. Since the cat command succeeded, it's exit code is 0, and that's what you see from print(x).

Python: How to get stdout after running os.system?

If all you need is the stdout output, then take a look at subprocess.check_output():

import subprocess

batcmd="dir"
result = subprocess.check_output(batcmd, shell=True)

Because you were using os.system(), you'd have to set shell=True to get the same behaviour. You do want to heed the security concerns about passing untrusted arguments to your shell.

If you need to capture stderr as well, simply add stderr=subprocess.STDOUT to the call:

result = subprocess.check_output([batcmd], stderr=subprocess.STDOUT)

to redirect the error output to the default output stream.

If you know that the output is text, add text=True to decode the returned bytes value with the platform default encoding; use encoding="..." instead if that codec is not correct for the data you receive.

How to return a value using a C file, then pick it up in python using the os.system?

According to os.system documentation:

On Unix, the return value is the exit status of the process encoded in
the format specified for wait(). Note that POSIX does not specify the
meaning of the return value of the C system() function, so the return
value of the Python function is system-dependent.

Use os.WEXITSTATUS to get the return code:

import os
x = os.system("./a.out")
print os.WEXITSTATUS(x)

---

Related Topics