I want to assign the output of a command I run using os.system
to a variable and prevent it from being output to the screen. But, in the below code ,the output is sent to the screen and the value printed for var
is 0, which I guess signifies whether the command ran successfully or not. Is there any way to assign the command output to the variable and also stop it from being displayed on the screen?
var = os.system("cat /etc/services")
print var #Prints 0
This question is related to
python
You might also want to look at the subprocess
module, which was built to replace the whole family of Python popen
-type calls.
import subprocess
output = subprocess.check_output("cat /etc/services", shell=True)
The advantage it has is that there is a ton of flexibility with how you invoke commands, where the standard in/out/error streams are connected, etc.
Python 2.6 and 3 specifically say to avoid using PIPE for stdout and stderr.
The correct way is
import subprocess
# must create a file object to store the output. Here we are getting
# the ssid we are connected to
outfile = open('/tmp/ssid', 'w');
status = subprocess.Popen(["iwgetid"], bufsize=0, stdout=outfile)
outfile.close()
# now operate on the file
I know this has already been answered, but I wanted to share a potentially better looking way to call Popen via the use of from x import x
and functions:
from subprocess import PIPE, Popen
def cmdline(command):
process = Popen(
args=command,
stdout=PIPE,
shell=True
)
return process.communicate()[0]
print cmdline("cat /etc/services")
print cmdline('ls')
print cmdline('rpm -qa | grep "php"')
print cmdline('nslookup google.com')
from os import system, remove
from uuid import uuid4
def bash_(shell_command: str) -> tuple:
"""
:param shell_command: your shell command
:return: ( 1 | 0, stdout)
"""
logfile: str = '/tmp/%s' % uuid4().hex
err: int = system('%s &> %s' % (shell_command, logfile))
out: str = open(logfile, 'r').read()
remove(logfile)
return err, out
# Example:
print(bash_('cat /usr/bin/vi | wc -l'))
>>> (0, '3296\n')```
The commands module is a reasonably high-level way to do this:
import commands
status, output = commands.getstatusoutput("cat /etc/services")
status is 0, output is the contents of /etc/services.
For python 3.5+ it is recommended that you use the run function from the subprocess module. This returns a CompletedProcess
object, from which you can easily obtain the output as well as return code. Since you are only interested in the output, you can write a utility wrapper like this.
from subprocess import PIPE, run
def out(command):
result = run(command, stdout=PIPE, stderr=PIPE, universal_newlines=True, shell=True)
return result.stdout
my_output = out("echo hello world")
# Or
my_output = out(["echo", "hello world"])
i do it with os.system temp file:
import tempfile,os
def readcmd(cmd):
ftmp = tempfile.NamedTemporaryFile(suffix='.out', prefix='tmp', delete=False)
fpath = ftmp.name
if os.name=="nt":
fpath = fpath.replace("/","\\") # forwin
ftmp.close()
os.system(cmd + " > " + fpath)
data = ""
with open(fpath, 'r') as file:
data = file.read()
file.close()
os.remove(fpath)
return data
Source: Stackoverflow.com