How to use subprocess command with pipes

Question

I want to use subprocess check output   with ps -A   grep  process name   I tried various solutions but so far nothing worked  Can someone guide me how to do it

User · Accepted Answer

To use a pipe with the subprocess module  you have to pass shell True   However  this isn t really advisable for various reasons  not least of which is security  Instead  create the ps and grep processes separately  and pipe the output from one into the other  like so   ps   subprocess Popen   ps    -A    stdout subprocess PIPE  output   subprocess check output   grep    process name    stdin ps stdout  ps wait     In your particular case  however  the simple solution is to call subprocess check output   ps    -A    and then str find on the output

User · Answer

Or you can always use the communicate method on the subprocess objects   cmd    ps -A grep  process name   ps   subprocess Popen cmd shell True stdout subprocess PIPE stderr subprocess STDOUT  output   ps communicate   0  print output    The communicate method returns a tuple of the standard output and the standard error

User · Answer

JKALAVIS solution is good  however I would add an improvement to use shlex instead of SHELL TRUE  below im grepping out Query times     bin python import subprocess import shlex  cmd    dig  8 8 4 4  notcp www google com grep  Query   ps   subprocess Popen cmd shell True stdout subprocess PIPE stderr subprocess STDOUT  output   ps communicate   0  print output

User · Answer

Using subprocess run import subprocess      ps   subprocess run   ps    -A    check True  capture output True  processNames   subprocess run   grep    process name                                  input ps stdout  capture output True  print processNames stdout

User · Answer

You can try the pipe functionality in sh py   import sh print sh grep sh ps  -ax     process name

User · Answer

See the documentation on setting up a pipeline using subprocess  http   docs python org 2 library subprocess html replacing-shell-pipeline  I haven t tested the following code example but it should be roughly what you want   query    process name  ps process   Popen   ps    -A    stdout PIPE  grep process   Popen   grep   query   stdin ps process stdout  stdout PIPE  ps process stdout close      Allow ps process to receive a SIGPIPE if grep process exits  output   grep process communicate   0

User · Answer

Also  try to use  pgrep  command instead of  ps -A   grep  process name

User · Answer

command    quot ps -A   grep  process name  quot  output   subprocess check output   quot bash quot    quot -c quot   command

User · Answer

After Python 3 5 you can also use       import subprocess      f   open  test txt    w       process   subprocess run   ls    -la    stdout subprocess PIPE  universal newlines True      f write process stdout      f close     The execution of the command is blocking and the output will be in process stdout

[python] How to use `subprocess` command with pipes

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