How to execute awk command inside python

Question

I am trying to run the following awk command inside python but I get a syntax error related to the quotes:

import subprocess
COMMAND = "df /dev/sda1 | awk /'NR==2 {sub("%","",$5); if ($5 >= 80) {printf "Warning! Space usage is %d%%", $5}}"

subprocess.call(COMMAND, shell=True)

I tried to escape the quotes but I am still getting the same error.

Possible duplicate of Python subprocess: pipe an image blob to imagemagick shell command — Maurice Meyer
– Maurice Meyer, Commented Dec 4, 2017 at 9:22
Proper escaping would be like this: COMMAND = "df /dev/sda1 | awk 'NR==2 {sub(\"%\",\"\",$5); if ($5 >= 80) {printf \"Warning! Space usage is %d%%\", $5}}'" — yolenoyer
– yolenoyer, Commented Dec 4, 2017 at 9:24
You have a unclosed quote. I suggest you running it in your terminal before you actually do it in python. — danieltan95
– danieltan95, Commented Dec 4, 2017 at 9:25
Use triple quotes on the COMMAND string. But why are you doing it like this? Just use awk, or just use Python. What's the point of using both of them? — PM 2Ring
– PM 2Ring, Commented Dec 4, 2017 at 9:26

Kaleb McGregor · Accepted Answer · 2017-12-04 09:25:47Z

4

You may want to put ''' or """ around the string since you have both ' and ".

import subprocess
COMMAND = '''"df /dev/sda1 | awk /'NR==2 {sub("%","",$5); if ($5 >= 80) {printf "Warning! Space usage is %d%%", $5}}"'''

subprocess.call(COMMAND, shell=True)

There also seems to be a relevant answer already for this as well: awk commands within python script

answered Dec 4, 2017 at 9:25

Kaleb McGregor

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2 Comments

user1919 Over a year ago

In that case I get a: No such file or directory

Kaleb McGregor Over a year ago

That could be the output for the df command. df should be used on filesystems and not on disks.

Yoni Rabinovitch · Accepted Answer · 2017-12-04 09:31:31Z

2

Try this:

import subprocess
COMMAND="df /dev/sda1 | awk 'NR==2 {sub(\"%\",\"\",$5); if ($5 >= 80) {printf \"Warning! Space usage is %d%%\", $5}}'"

subprocess.Popen(COMMAND,stdin=subprocess.PIPE,stdout=subprocess.PIPE, shell=True).stdout.read()

answered Dec 4, 2017 at 9:31

Yoni Rabinovitch

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1 Comment

alper Over a year ago

shell=True is not recommended

alper · Accepted Answer · 2021-01-03 22:10:02Z

I was writing a python script for my deployment purpose and one part of the script was to explicitely kill the process if its not stopped successfully.

Below is the python code which actually performs Find the processId of the process named myApplication ps -ef | grep myApplication | grep -v grep | awk {'print $2'} and then perform kill -9 PID //where PID is output of earlier command

  import subprocess
  import signal

  def killApplicationProcessIfStillRunning(app_name):
      p1 = subprocess.Popen(['ps', '-ef'], stdout=subprocess.PIPE)
      p2 = subprocess.Popen(['grep', app_name],stdin=p1.stdout, stdout=subprocess.PIPE)
      p3 = subprocess.Popen(['grep', '-v' , 'grep'],stdin=p2.stdout, stdout=subprocess.PIPE)
      p4 = subprocess.Popen(['awk', '{print $2}'],stdin=p3.stdout, stdout=subprocess.PIPE)
      out, err = p4.communicate()
      if out:
          print 'Attempting to kill '+app_name +' process with PID ' +out.splitlines()[0]
          os.kill(int(out.splitlines()[0]),signal.SIGKILL)

Now invoke the above method as

killApplicationProcessIfStillRunning(myApplication)

Hope it helps someone.

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