running multiple bash commands with subprocess

Question

If I run echo a; echo b in bash the result will be that both commands are run. However if I use subprocess then the first command is run, printing out the whole of the rest of the line. The code below echos a; echo b instead of a b, how do I get it to run both commands?

import subprocess, shlex def subprocess_cmd(command):     process = subprocess.Popen(shlex.split(command), stdout=subprocess.PIPE)     proc_stdout = process.communicate()[0].strip()      print proc_stdout  subprocess_cmd("echo a; echo b") 

Answer 1

You have to use shell=True in subprocess and no shlex.split:

import subprocess  command = "echo a; echo b"  ret = subprocess.run(command, capture_output=True, shell=True)  # before Python 3.7: # ret = subprocess.run(command, stdout=subprocess.PIPE, shell=True)  print(ret.stdout.decode()) 

returns:

a b 

Answer 2

I just stumbled on a situation where I needed to run a bunch of lines of bash code (not separated with semicolons) from within python. In this scenario the proposed solutions do not help. One approach would be to save a file and then run it with Popen, but it wasn't possible in my situation.

What I ended up doing is something like:

commands = ''' echo "a" echo "b" echo "c" echo "d" '''  process = subprocess.Popen('/bin/bash', stdin=subprocess.PIPE, stdout=subprocess.PIPE) out, err = process.communicate(commands) print out 

So I first create the child bash process and after I tell it what to execute. This approach removes the limitations of passing the command directly to the Popen constructor.