bash Cookbook

Automating a Process Using Phases

Problem

You have a long job or process you need to automate, but it may require manual intervention and you need to be able to restart at various points in the progress. You might use a GOTO to jump around, but bash doesn’t have that.

Solution

Use a case statement to break your script up into sections or phases.

First, we’ll define a standardized way to get answers from the user:

# cookbook filename: func_choice

function choice {
    # Let the user make a choice about something and return a standardized
    # answer. How the default is handled and what happens next is up to
    # the if/then after the choice in main

    local answer
    printf "%b" "\a"        # Ring the bell
    read -p "$*" answer
    case "$answer" in
        [yY1] ) choice='y';;
        [nN0] ) choice='n';;
        *     ) choice="$answer";;
    esac
} # end of function choice

Then, we’ll set up our phases:

# cookbook filename: using_phases # Main Loop until [ "$phase" = "Finished." ]; do case $phase in phase0 ) ThisPhase=0 NextPhase="$(( $ThisPhase + 1 ))" echo '############################################' echo "Phase$ThisPhase = Initialization of FooBarBaz build" # Things that should only be initialized at the beginning of a # new build cycle go here # ... echo "Phase${ThisPhase}=Ending" phase="phase$NextPhase" ;; # ... phase20 ) ThisPhase=20 NextPhase="$(( $ThisPhase + 1 ))" echo '############################################' echo "Phase$ThisPhase = Main processing for FooBarBaz build" # ... choice "[P$ThisPhase] Do we need to stop and fix anything? ...