Automate repetitive tasks using shell scripts

In day to day application development especially building Microservice architecture based application using Spring Boot and Kubernetes, during development we tend to build artifacts and images multiple times for validating the changes.

In this blog have detail how to automate day to day development tasks like using mvn and kubectl commands, both the commands configured in the Git Bash as alias in the .bashrc file. Demonstrated how to run the commands in bash terminal by passing arguments.

Prerequisites

Basic understanding of Shell scripting
Kind CLI installed (Docker Desktop)
Git Bash Installed

Automate mvn command as a alias in Git Bash

To set an alias command for maven command
- Add below command in $HOME/.bashrc file in windows.

alias runMvn='mvnFunc(){ POMFILE="pom.xml"; if [ -f "$POMFILE" ]; then mvn "$@" clean install; else echo "$POMFILE not found"; fi; unset -f mvnFunc; }; mvnFunc'

If the Git Bash is already opened, to apply the changes to reflect on the open shell issue $ source ~/.bashrc.
About the above code,
- Defines a simple shell function, which checks is the pom.xml file exist in the current directory.
- The usage of "$@" is to use the argument in the mvn command passed as argment.

Command usage in Git Bash

Executing the alias command (without any argument) like below will run mvn clean install
```
$ runMvn
```
Executing alias command (with argument -DskipTest) like below will execute mvn -DskipTests clean install

$ runMvn -DskipTests

Automate kubectl create and delete resource from yaml file

To automate the kubectl apply and delete resources we create a simple shell script.
The shell script will be configured in the ~/.bashrc,

alias runK8SScript='kubeFunc(){ TMPPWD=$(pwd); cd /c/shellScript/; sh runK8SScript.sh "$@" ; cd $TMPPWD; unset -f kubeFunc; }; kubeFunc'

Create a Script (.sh) file named runK8SScript.sh with the below content.
- Below script can be extended say if we have mulitple yaml file we can utilize it.
- Likewise we can use helm to deploy charts as well.
Logic in below script is self explanatory, script uses getopts, to get user option based on which the kubectl apply and kubectl delete command will be executed.

#!/usr/bin/env bash

ACTION=

handleResource()
{
  INPUT_ACTION=$1
  CONTEXT=$2
  MANIFEST_PATH=$3
  MANIFEST_FILE=$4

  echo "[DEBUG] Executing .. kubectl --context $CONTEXT $INPUT_ACTION -f $MANIFEST_PATH$MANIFEST_FILE"
  # if namespace not provied within the manifest 
  # pass it to this function to a new variable
  kubectl --context $CONTEXT $INPUT_ACTION $MANIFEST_PATH$MANIFEST_FILE
}

info() { echo -e "$0 -<option> <action> \nusage:" && grep " .)\ #" $0 | sed 's/)\ ##//g' | sed 's/\([cd] \)/-\1/g';}

while getopts ":c:d:" option; do
  case $option in
    c) ## create
      echo "option provided $OPTARG"
      ACTION="C"
      ;;
    d) ## delete
      echo "option provided $OPTARG"
      ACTION="D"
      ;;
    *) 
       echo "not correct usage, use "
       info;
       exit 0;
  esac
done

if [[ -z "$ACTION" ]]; then 
  echo "other available options"
  info
fi

# using kind and the cluster context is defined
CONTEXT_TO_DEPLOY="kind-demo1"
# use / at the end
MANIFEST_FOLDER="/c/shellScript/manifest/"

#yaml file
MANIFEST_FILE_NAME="nginxDeploy.yaml"


if [[ "$ACTION" == "C" || -z "$ACTION" ]]; then
    SKIP=0
    read -p "Do you want to create resource (y/n)? - " input
    if [[ ! -z "$input" && !( "$input" == "y" || "$input" == "Y" || "$input" == "yes" || "$input" == "YES" ) ]]; then 
       echo "Resource creation ignored"
       SKIP=1
    fi
    if (( $SKIP == 0 )); then 
      echo "Creating resources"
      handleResource "apply" $CONTEXT_TO_DEPLOY $MANIFEST_FOLDER $MANIFEST_FILE_NAME
    fi
fi

if [[ "$ACTION" == "D" || -z "$ACTION" ]]; then 
    SKIP=0
    read -p "Do you want to delete resource (y/n)? - " input
    if [[ ! -z "$input" && !( "$input" == "y" || "$input" == "Y" || "$input" == "yes" || "$input" == "YES" ) ]]; then 
       echo "Resource deletion ignored"
       SKIP=1
    fi
    if (( $SKIP == 0 )); then 
        echo "Deleting resource"
        handleResource "delete" $CONTEXT_TO_DEPLOY $MANIFEST_FOLDER $MANIFEST_FILE_NAME
    fi
fi

Usage of the alias command

$ runK8SScript

Output with no argument

$ runK8SScript -c create

Output with create argument

$ runK8SScript -d delete

thirumurthi