running multiple bash commands with subprocess

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")
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>>> command = "echo a; echo b"
>>> shlex.split(command);
['echo', 'a; echo', 'b']

so, the problem is shlex module do not handle ";"

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最佳答案

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
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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.

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Join commands with "&&".

os.system('echo a > outputa.txt && echo b > outputb.txt')
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If you're only running the commands in one shot then you can just use subprocess.check_output convenience function:

def subprocess_cmd(command):
output = subprocess.check_output(command, shell=True)
print output
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import subprocess
cmd = "vsish -e ls /vmkModules/lsom/disks/  | cut -d '/' -f 1  | while read diskID  ; do echo $diskID; vsish -e cat /vmkModules/lsom/disks/$diskID/virstoStats | grep -iE 'Delete pending |trims currently queued' ;  echo '====================' ;done ;"




def subprocess_cmd(command):
process = subprocess.Popen(command,stdout=subprocess.PIPE, shell=True)
proc_stdout = process.communicate()[0].strip()
for line in proc_stdout.decode().split('\n'):
print (line)


subprocess_cmd(cmd)
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Got errors like when I used capture_output=True

TypeError: __init__() got an unexpected keyword argument 'capture_output'

After made changes like as below and its works fine

import subprocess


command = '''ls'''


result = subprocess.run(command, stdout=subprocess.PIPE,shell=True)


print(result.stdout.splitlines())

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