Store output of subprocess Popen call in a string

Question

I m trying to make a system call in Python and store the output to a string that I can manipulate in the Python program      usr bin python import subprocess p2   subprocess Popen  ntpq -p     I ve tried a few things including some of the suggestions here   Retrieving the output of subprocess call    but without any luck

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In Python 3 7 a new keyword argument capture output was introduced for subprocess run  Enabling the short and simple   import subprocess  p   subprocess run  echo  hello world     capture output True  shell True  encoding  utf8   assert p stdout     hello world  n

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For python 3 5 I put up function based on previous answer  Log may be removed  thought it s nice to have  import shlex from subprocess import check output  CalledProcessError  STDOUT   def cmdline command       log  cmdline     format command       cmdArr   shlex split command      try          output   check output cmdArr   stderr STDOUT  decode           log  Success     format output       except  CalledProcessError  as e          output   e output decode           log  Fail     format output       except  Exception  as e          output   str e           log  Fail     format e       return str output    def log msg       msg   str msg      d date   datetime datetime now       now   str d date strftime   Y- m- d  H  M  S        print now         msg      if   LOG FILE  in globals             with open LOG FILE   a   as myfile              myfile write now         msg     n

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This was perfect for me   You will get the return code  stdout and stderr in a tuple   from subprocess import Popen  PIPE  def console cmd       p   Popen cmd  shell True  stdout PIPE      out  err   p communicate       return  p returncode  out  err    For Example   result   console  ls -l   print  returncode   s    result 0  print  output   s    result 1  print  error   s    result 2

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import os     list   os popen  pwd   read     In this case you will only have one element in the list

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The accepted answer is still good  just a few remarks on newer features  Since python 3 6  you can handle encoding directly in check output  see documentation  This returns a string object now   import subprocess  out   subprocess check output   ls    -l    encoding  utf-8     In python 3 7  a parameter capture output was added to subprocess run    which does some of the Popen PIPE handling for us  see the python docs     import subprocess  p2   subprocess run   ls    -l    capture output True  encoding  utf-8   p2 stdout

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This works perfectly for me   import subprocess try       prints results and merges stdout and std     result   subprocess check output  echo  USERNAME    stderr subprocess STDOUT  shell True      print result      causes error and merges stdout and stderr     result   subprocess check output  copy testfds   stderr subprocess STDOUT  shell True  except subprocess CalledProcessError  ex    error code  lt  gt  0      print  --------error------      print ex cmd     print ex message     print ex returncode     print ex output   contains stdout and stderr together

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I wrote a little function based on the other answers here   def pexec  args       return subprocess Popen args  stdout subprocess PIPE  communicate   0  rstrip     Usage   changeset   pexec  hg   id   --id   branch   pexec  hg   id   --branch   revnum   pexec  hg   id   --num   print   s    s   s      revnum  changeset  branch

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subprocess Popen  http   docs python org 2 library subprocess html subprocess Popen  import subprocess  command    ntpq -p     the shell command process   subprocess Popen command  stdout subprocess PIPE  stderr None  shell True    Launch the shell command  output   process communicate    print output 0    In the Popen constructor  if shell is True  you should pass the command as a string rather than as a sequence  Otherwise  just split the command into a list    command     ntpq    -p      the shell command process   subprocess Popen command  stdout subprocess PIPE  stderr None    If you need to read also the standard error  into the Popen initialization  you can set stderr to subprocess PIPE or to subprocess STDOUT   import subprocess  command    ntpq -p     the shell command process   subprocess Popen command  stdout subprocess PIPE  stderr subprocess PIPE  shell True    Launch the shell command  output  error   process communicate

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import subprocess output   str subprocess Popen  ntpq -p  shell   True stdout   subprocess PIPE   stderr   subprocess STDOUT  communicate   0     This is one line solution

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Assuming that pwd is just an example  this is how you can do it   import subprocess  p   subprocess Popen  pwd   stdout subprocess PIPE  result   p communicate   0  print result   See the subprocess documentation for another example and more information

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This worked for me for redirecting stdout  stderr can be handled similarly    from subprocess import Popen  PIPE pipe   Popen path  stdout PIPE  text   pipe communicate   0    If it doesn t work for you  please specify exactly the problem you re having

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for Python 2 7  the idiomatic answer is to use subprocess check output    You should also note the handling of arguments when invoking a subprocess  as it can be a little confusing      If args is just single command with no args of its own  or you have shell True set   it can be a string   Otherwise it must be a list   for example    to invoke the ls command  this is fine   from subprocess import check call check call  ls     so is this   from subprocess import check call check call   ls       however  if you want to pass some args to the shell command  you can t do this   from subprocess import check call check call  ls -al     instead  you must pass it as a list   from subprocess import check call check call   ls    -al      the shlex split   function can sometimes be useful to split a string into shell-like syntax before creating a subprocesses     like this   from subprocess import check call import shlex check call shlex split  ls -al

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In Python 2 7 or Python 3  Instead of making a Popen object directly  you can use the subprocess check output   function to store output of a command in a string   from subprocess import check output out   check output   ntpq    -p      In Python 2 4-2 6  Use the communicate method   import subprocess p   subprocess Popen   ntpq    -p    stdout subprocess PIPE  out  err   p communicate     out is what you want   Important note about the other answers  Note how I passed in the command  The  ntpq -p  example brings up another matter  Since Popen does not invoke the shell  you would use a list of the command and options     ntpq    -p

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The following captures stdout and stderr of the process in a single variable   It is Python 2 and 3 compatible   from subprocess import check output  CalledProcessError  STDOUT  command     ls    -l   try      output   check output command  stderr STDOUT  decode       success   True  except CalledProcessError as e      output   e output decode       success   False   If your command is a string rather than an array  prefix this with   import shlex command   shlex split command

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Use check output method of subprocess module import subprocess  address    192 168 x x  res   subprocess check output   ping   address   -c    3     Finally parse the string for line in res splitlines     Hope it helps  happy coding

[python] Store output of subprocess.Popen call in a string

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