Question

I am a Python Novice so please help me out…

#!/usr/bin/python -tt

import sys
import commands

def runCommands():
  f = open("a.txt", 'r')
  for line in f:  # goes through a text file line by line
    cmd = 'ls -l ' + line 
    print "printing cmd = " + cmd,
    (status, output) = commands.getstatusoutput(cmd)
  if status:    ## Error case, print the command's output to stderr and exit
      print "error"
      sys.stderr.write(output)
      sys.exit(1)
  print output
  f.close()

def main():
  runCommands()

# Standard boilerplate at end of file to call main() function.
if __name__ == '__main__':
  main()

I run it as follows:

$python demo.py
sh: -c: line 1: syntax error near unexpected token `;'
sh: -c: line 1: `; } 2>&1'
error

Running less $(which python) says:

#!/bin/sh bin=$(cd $(/usr/bin/dirname "$0") && pwd) exec -a "$0" "$bin/python2.5" "$@"

If i remove for loop then it works fine

$cat a.txt
dummyFile


$ls -l dummyFile
-rw-r--r-- 1 blah blah ...................

$python demo.py
printing cmd = ls -l dummyFile
sh: -c: line 1: syntax error near unexpected token `;'
sh: -c: line 1: `; } 2>&1'
error

I am using ‘ls’ just for showing the problem. Actually i wanna use some internal shell scripts so i have to run this python script in this way only.

Answer 1

The problem is caused by this line:

    cmd = 'ls -l ' + line

it should be modified to:

    cmd = 'ls -l ' + line.strip() 

When you read the line from your text file, you also read the trailing \n. You need to strip this so that it works. The getstatusoutput() doesn’t like the trailing newline. See this interactive test (which is how I verified it):

In [7]: s, o = commands.getstatusoutput('ls -l dummyFile')

In [8]: s, o = commands.getstatusoutput('ls -l dummyFile\n')
sh: Syntax error: ";" unexpected