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I am trying to automate fdisk utility on Linux in order to delete partitions on the attached disk device (USB /dev/sdb in this case) by using Python 3.

The script should execute the following commands:

1). sudo fdisk /dev/sdb // Executing fdisk on /dev/sdb

Welcome to fdisk (util-linux 2.29). Changes will remain in memory only, until you decide to write them. Be careful before using the write command.

Command (m for help): 2). d /dev/sdb // Trying to delete /dev/sdb partition.

Partition number (1-4, default 4): 3). 2 // Partition number 2

This is my Python code so far:

proc = subprocess.Popen(["sudo", "fdisk", "/dev/sdb"], stdin=subprocess.PIPE)    
proc.communicate(b'd /dev/sdb')    
proc.communicate(b'2')

Line1 and Line2 works perfectly fine, however Line3 gives me the following error:

Welcome to fdisk (util-linux 2.29).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.


Command (m for help): Partition number (1-4, default 4): Traceback (most recent call last):
File "./testing.py", line 83, in <module>    
proc.communicate(b'2')    
File "/usr/lib/python3.5/subprocess.py", line 786, in communicate    
self._stdin_write(input)   
File "/usr/lib/python3.5/subprocess.py", line 741, in _stdin_write    
self.stdin.write(input)    
ValueError: write to closed file

Is it possible to use subprocesses to achieve this task without a user having to interact with the program? Any assistance will be highly appreciated. Thanks.

BrightA
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1 Answers1

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The Proc.communicate() function will effectively end the bytes with an EOF signal. So what you can do is treat all your commands as being part of the same file. Try:

proc.communicate(b'd /dev/sdb\n2')

The \n is what you're sending to the program when you hit the enter key.

Daniel Abercrombie
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