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good_practices.md

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Bash scripting good practices

  • Script should return zero on success and non-zero on failure.

Good practices on functions

  • Function documentation example
function hello_world() {
  # @description This function prints the message
  # @description hello world on to the terminal
  echo "Hello world"

}
  • Functions are like scripts they return only integers. Use global variables RESULT, EXCEPTION and EXCEPTION_MSG to store the result, error code and error message respectively.

Variables

  • use local keyword to define local variables, else the variables become globally available within the script after the function has been executed atleast once. Use readonly variables whenever possible. Use the readonly shell builtin. help readonly to knwo about the usage of this shell builtin.

  • Assign meaningful names to the function parameters since functions receive parameters as special variables like $1, $2 etc.

  • Raise error on accessing unset variable access using the command set -o nounset.

Traps

function Main__interruptHandler() {
    # @description signal handler for SIGINT
    echo "SIGINT caught"
    exit
}
function Main__terminationHandler() {
    # @description signal handler for SIGTERM
    echo "SIGTERM caught"
    exit
}
function Main__exitHandler() {
    # @description signal handler for end of the program (clean or unclean).
    # probably redundant call, we already call the cleanup in main.
    exit
}

trap Main__interruptHandler INT
trap Main__terminationHandler TERM
trap Main__exitHandler EXIT

function Main__main() {
    # body
}

# catch signals and exit
trap exit INT TERM EXIT

Main__main "$@"

References