CODEWITHSUNDEEP
pythonsubprocesswaitpopen
michele
michele

Reputation: 26598

Python popen command. Wait until the command is finished

I have a script where I launch with popen a shell command. The problem is that the script doesn't wait until that popen command is finished and go continues right away.

om_points = os.popen(command, "w")
.....

How can I tell to my Python script to wait until the shell command has finished?

Upvotes: 112

Views: 265727

Answers (7)

Barsha Lamichhane
Barsha Lamichhane

Reputation: 1

I think process.communicate() would be suitable for output having small size. For larger output it would not be the best approach.

Upvotes: 0

Alberto
Alberto

Reputation: 396

Force popen to not continue until all output is read by doing:

os.popen(command).read()

Upvotes: 24

simibac
simibac

Reputation: 8610

wait() works fine for me. The subprocesses p1, p2 and p3 are executed at the same. Therefore, all processes are done after 3 seconds. 

import subprocess

processes = []

p1 = subprocess.Popen("sleep 3", stdout=subprocess.PIPE, shell=True)
p2 = subprocess.Popen("sleep 3", stdout=subprocess.PIPE, shell=True)
p3 = subprocess.Popen("sleep 3", stdout=subprocess.PIPE, shell=True)

processes.append(p1)
processes.append(p2)
processes.append(p3)

for p in processes:
    if p.wait() != 0:
        print("There was an error")

print("all processed finished")

Upvotes: 7

Chidhambararajan NRM
Chidhambararajan NRM

Reputation: 423

Let the command you are trying to pass be 

os.system('x')

then you covert it to a statement

t = os.system('x')

now the python will be waiting for the output from the commandline so that it could be assigned to the variable t.

Upvotes: 15

unholysampler
unholysampler

Reputation: 17341

Depending on how you want to work your script you have two options. If you want the commands to block and not do anything while it is executing, you can just use subprocess.call.

#start and block until done
subprocess.call([data["om_points"], ">", diz['d']+"/points.xml"])

If you want to do things while it is executing or feed things into stdin, you can use communicate after the popen call.

#start and process things, then wait
p = subprocess.Popen([data["om_points"], ">", diz['d']+"/points.xml"])
print "Happens while running"
p.communicate() #now wait plus that you can send commands to process

As stated in the documentation, wait can deadlock, so communicate is advisable.

Upvotes: 139

Touchstone
Touchstone

Reputation: 5982

You can you use subprocess to achieve this.

import subprocess

#This command could have multiple commands separated by a new line \n
some_command = "export PATH=$PATH://server.sample.mo/app/bin \n customupload abc.txt"

p = subprocess.Popen(some_command, stdout=subprocess.PIPE, shell=True)

(output, err) = p.communicate()  

#This makes the wait possible
p_status = p.wait()

#This will give you the output of the command being executed
print "Command output: " + output

Upvotes: 45

Olivier Verdier
Olivier Verdier

Reputation: 49236

What you are looking for is the wait method.

Upvotes: 7

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