Scripting Classroomnotes 27/Apr/2023

Contents

What is Scripting and How is it different from programming?

• Every scripting language is a Programming Language, The one theoritical difference is programming languages are compile and then executed where as scripting languages donot have extra compilation step.

Live Example

• We have written two programs
• shell script

#!/bin/bash
tempfile="/tmp/available.$$"
trap "rm -f $tempfile" EXIT

cat << 'EOF' > $tempfile
    { sum += $4 }
END { mb = sum/1024
      gb = mb/1024
      printf "%.0f MB (%.2fGB) of availble diskspace\n", mb, gb
    }
EOF

df -k | awk -f $tempfile
exit 0

• Python script

#!/usr/bin/env python3

import shutil
path = "/"
total, used, free = shutil.disk_usage(path)
print("Total: %d GiB" % (total // (2**30)))
print("used: %d GiB" % (used // (2**30)))
print("free: %d GiB" % (free // (2**30)))

Approach – Part 1

• Any script is a set of instructions executed line by line
• To become effective understanding flow of the program/script is essentioal

Lets write a script to install docker

• create a file (installdocker.sh) with following content

#!/bin/bash
curl -fsSL https://get.docker.com -o get-docker.sh
sh get-docker.sh

• Now give execute permissions and run the script <path>/installdocker.sh

Exercises

• Write a shell script
  • to install jenkins with java 11
  • to install jenkins with java 17
  • to install kubernetes (using kubeadm) skip init
• Note: all the scripts will be run as a root user