AWS Linux: ensure that flaky script keeps running

Question

I am trying to write a nanny script, to use in AWS's Linux terminal, to run a python script that can be a bit flakey at times. I am very new to using the terminal / bash, etc, so I could be missing something totally obvious / second nature to others. Here is what I have:

#! /usr/bin/env bash

while true:
    script.py
    sleep 1  # pause, so if script.py immediately dies we don't burn a core

I put the above code in a runProgram.sh file, located in the same directory as my python program. I then went into the terminal, and ran:

chmod -x runProgram.sh

followed by:

bash runProgram.sh

The terminal throws the following error:

"line 6: syntax error: unexpected end of file".

I took the bash code right from a stackoverflow response though, so I'm not sure what I'm missing in terms of syntax etc. any help is appreciated!

added the link. I'm not sure what you mean by CRLF line terminators? I'm totally new at this. — keynesiancross, Jul 11 '22 at 14:15
Also - why not have the while loop inside the python script? & call the python script directly? — tenacity, Jul 11 '22 at 14:16
Also why are you doing `chmod -x run Program.sh` Instead you must be giving it execute permissions by doing `chmod +x runProgram.sh` — tenacity, Jul 11 '22 at 14:20
Yeah, I seriously have no clue what I’m doing. If you could lay it out for me like you would a 5yr old that would be great. — keynesiancross, Jul 11 '22 at 14:23
Couple things. **1** remove the space between `#!` and `/usr/bin/env`. **2** you could put the loop and sleep directly in the python script (like @HariharanRagothaman mentionned). **3** CRLF: when a file is created using a Windows editor (ex notepad) the files end with CR (carriage return) and LF (line feed). These can cause issues when you run the files on Linux. See https://stackoverflow.com/questions/2613800/how-to-convert-dos-windows-newline-crlf-to-unix-newline-lf for ways to remove them. — Nic3500, Jul 11 '22 at 14:24

score 1 · Accepted Answer · answered Jul 11 '22 at 14:29

1

I was able to reproduce your issue, by directly copy-pasting the snippet you pasted.

Modified your script slightly. Feel free to copy-paste directly.

#!/bin/bash
while [ True ]
do
  python3 script.py
done

To know more about CRLF

Also this is my current bash version

/tmp:$ bash --version
GNU bash, version 3.2.57(1)-release (arm64-apple-darwin21)
Copyright (C) 2007 Free Software Foundation, Inc.

Why does chmod +x do?

It essentially gives execute level permissions for your script of interest.

answered Jul 11 '22 at 14:29

tenacity

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1
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Thanks a lot. So do I need to do that Chmod thing before I run this file? – keynesiancross Jul 11 '22 at 14:39
Yes, for the bash script & the python script. – tenacity Jul 11 '22 at 14:42
Is everything working for you now? @keynesiancross – tenacity Jul 11 '22 at 14:43
I had to jump away from the computer - I’ll check back in 30min or so – keynesiancross Jul 11 '22 at 15:05
Where should I write this file by the way? I was transferring it from my PyCharm (windows) into my AWS Linux – keynesiancross Jul 11 '22 at 15:06
If you are transferring from PyCharm to your AWS Linux - you are susceptible for CLRF issues again. I would say directly copy it to your linux console from this post (OR) change your Pycharm settings to support Linux line endings. – tenacity Jul 11 '22 at 15:12
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/246349/discussion-between-hariharan-ragothaman-and-keynesiancross). – tenacity Jul 11 '22 at 15:16

score 0 · Answer 2 · answered Jul 11 '22 at 14:43

This command makes the file non executable:

chmod -x runProgram.sh

What you want to do is to make executable like so:

chmod +x runProgram.sh

Turn both, your shell script and python script executable.

then you can run it by typing ./runProgram.sh or bash runProgram.sh.

AWS Linux: ensure that flaky script keeps running

2 Answers2

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