Retrieving the output of subprocess call

Question

How can I get the output of a process run using subprocess call     Passing a StringIO StringIO object to stdout gives this error   Traceback  most recent call last     File   lt stdin gt    line 1  in  lt module gt    File   Library Frameworks Python framework Versions 2 6 lib python2 6 subprocess py   line 444  in call     return Popen  popenargs    kwargs  wait     File   Library Frameworks Python framework Versions 2 6 lib python2 6 subprocess py   line 588  in   init       errread  errwrite    self  get handles stdin  stdout  stderr    File   Library Frameworks Python framework Versions 2 6 lib python2 6 subprocess py   line 945  in  get handles     c2pwrite   stdout fileno   AttributeError  StringIO instance has no attribute  fileno   gt  gt  gt

User · Accepted Answer

Output from subprocess call   should only be redirected to files   You should use subprocess Popen   instead  Then you can pass subprocess PIPE for the stderr  stdout  and or stdin parameters and read from the pipes by using the communicate   method   from subprocess import Popen  PIPE  p   Popen   program    arg1    stdin PIPE  stdout PIPE  stderr PIPE  output  err   p communicate b input data that is passed to subprocess  stdin   rc   p returncode   The reasoning is that the file-like object used by subprocess call   must have a real file descriptor  and thus implement the fileno   method  Just using any file-like object won t do the trick   See here for more info

User · Answer

I recently just figured out how to do this  and here s some example code from a current project of mine   Getting the random picture   First find all pictures  import shlex  subprocess cmd    find    Pictures  -regex  quot     JPG  NEF  jpg   quot     cmd   raw input  quot shell  quot   args   shlex split cmd  output error   subprocess Popen args stdout   subprocess PIPE  stderr  subprocess PIPE  communicate    Another way to get output  output   subprocess Popen args stdout   subprocess PIPE  stdout ber   raw input  quot search complete  display results  quot   print output      and on to the selection process      You now have the output of the command stored in the variable  quot output quot     quot stdout   subprocess PIPE quot  tells the class to create a file object named  stdout  from within Popen   The communicate   method  from what I can tell  just acts as a convenient way to return a tuple of the output and the errors from the process you ve run   Also  the process is run when instantiating Popen

User · Answer

If you have Python version    2 7  you can use subprocess check output which basically does exactly what you want  it returns standard output as string    Simple example  linux version  see note    import subprocess  print subprocess check output   ping    -c    1    8 8 8 8      Note that the ping command is using linux notation  -c for count   If you try this on Windows remember to change it to -n for same result   As commented below you can find a more detailed explanation in this other answer

User · Answer

I have the following solution  It captures the exit code  the stdout  and the stderr too of the executed external command   import shlex from subprocess import Popen  PIPE  def get exitcode stdout stderr cmd               Execute the external command and get its exitcode  stdout and stderr              args   shlex split cmd       proc   Popen args  stdout PIPE  stderr PIPE      out  err   proc communicate       exitcode   proc returncode           return exitcode  out  err  cmd            arbitrary external command  e g   python mytest py  exitcode  out  err   get exitcode stdout stderr cmd    I also have a blog post on it here   Edit  the solution was updated to a newer one that doesn t need to write to temp  files

User · Answer

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

User · Answer

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   from subprocess import PIPE  run  command     echo    hello   result   run command  stdout PIPE  stderr PIPE  universal newlines True  print result returncode  result stdout  result stderr

User · Answer

In Ipython shell   In  8   import subprocess In  9   s subprocess check output   echo    Hello World     In  10   s Out 10    Hello World  n    Based on sargue s answer  Credit to sargue

[python] Retrieving the output of subprocess.call()

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