the shell script in the claculation of NLO

I wanted to compute NLO process (p p> t t~) [QCD] for 50 times in MG5, I wrote a shell script for this computation, but I got an error every time I run it, as following:
ablikim@ablikim:~/ttbar555/bin$ bash run_PDF.sh
No module named madgraph
INFO: ************************************************************
* *
* W E L C O M E to M A D G R A P H 5 *
* a M C @ N L O *
* *
* * * *
* * * * * *
* * * * * 5 * * * * *
* * * * * *
* * * *
* *
* VERSION 5.2.3.3 20xx-xx-xx *
* *
* The MadGraph5_aMC@NLO Development Team - Find us at *
* http://amcatnlo.cern.ch *
* *
* Type 'help' for in-line help. *
* *
************************************************************
INFO: load configuration from /home/ablikim/ttbar555/Cards/amcatnlo_configuration.txt
INFO: load configuration from /home/ablikim/Documents/tools/MG5_aMC_v2_3_3/input/mg5_configuration.txt
INFO: load configuration from /home/ablikim/ttbar555/Cards/amcatnlo_configuration.txt
Using default text editor "vi". Set another one in ./input/mg5_configuration.txt
Using default eps viewer "evince". Set another one in ./input/mg5_configuration.txt
Using default web browser "firefox". Set another one in ./input/mg5_configuration.txt
launch launch.txt
Command "launch launch.txt" interrupted with error:
InvalidCmd : launch.txt is not a valid mode, please use "LO", "NLO", "aMC@NLO" or "aMC@LO"
Please report this bug on https://bugs.launchpad.net/madgraph5
More information is found in 'ME5_debug'.
Please attach this file to your report.
quit
INFO:

#!/bin/bash
function main {

 for (( i=1; i<=50; i++ ))
 do

  #run MadGraph
  ./generate_events launch.txt

 done
}
main

launch.txt :

fixed_order=ON

please help me soon, thank you so much!

Best regards
 Ablikim