python + run complicated shell command via python script

Question

We want to run the following shell command by python script ( we use python version 2.7 )

echo hadoop-hdfs-namenode - 2.6.4.0-91| grep hadoop-hdfs-namenode | awk '{print $NF}' | awk '{printf "%.1f\n", $NF}'
2.6

So I create the following python script to get the results - 2.6

import os

os.system("echo hadoop-hdfs-namenode - 2.6.4.0-91| grep hadoop-hdfs-namenode | awk '{print $NF}' | awk '{printf "%.1f\n", $NF}' ")

but when I run it we get

 os.system("echo hadoop-hdfs-namenode - 2.6.4.0-91| grep hadoop-hdfs-namenode | awk '{print $NF}' | awk '{printf "%.1f\n", $NF}' ")
                                                                                                                        ^
SyntaxError: invalid syntax

Is it possible to run this complicated shell via python ? , in order to get the expected results - 2.6

And how to fix my syntax?

You could also use the newer subprocess module that is intended to replace os.system calls. — mabergerx
– mabergerx, Commented Jul 8, 2020 at 11:20
in addition to what @mabergerx said its always a good idea to check return codes from each step so you know when an error happens — John Scott Stensland
– John Scott Stensland, Commented Jul 8, 2020 at 11:23
I get this after the update per you recommendation - awk: cmd. line:1: {printf %.1f awk: cmd. line:1: ^ syntax error awk: cmd. line:1: {printf %.1f awk: cmd. line:1: ^ unexpected newline or end of string sh: line 1: , $NF}: command not found — jessica
– jessica, Commented Jul 8, 2020 at 11:31

dejanualex · Accepted Answer · 2020-07-08 12:01:03Z

4

escape " and \n : os.system("echo hadoop-hdfs-namenode - 2.6.4.0-91| grep hadoop-hdfs-namenode | awk '{print $NF}' | awk '{printf \" %.1f\\n \", $NF}' ") .

As a side note os.system will execute the command (a string) in a subshell and return the return code of the command , if you need the output take a look at the subprocess module: https://docs.python.org/3/library/subprocess.html

edited Jul 8, 2020 at 12:01

answered Jul 8, 2020 at 11:18

dejanualex

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2 Comments

jessica Over a year ago

I get this error - awk: cmd. line:1: {printf "%.1f awk: cmd. line:1: ^ unterminated string awk: cmd. line:1: {printf "%.1f awk: cmd. line:1: ^ syntax error

dejanualex Over a year ago

Be careful you need to escape :

os.system("echo hadoop-hdfs-namenode - 2.6.4.0-91| grep hadoop-hdfs-namenode | awk '{print $NF}' | awk '{printf \" %.1f\\n \", $NF}' ")

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