bash_backoff.sh

#!/usr/bin/env bash

# Usage: retry <num-retries> <command> [arguments]
function retry {
    local retries=$1
    shift
    local cmd=("$@")

    case "${retries}" in
    '' | *[!0-9]*)
        echo "retries parameter must be a number greater than 0" >&2
        return 1
        ;;

    *)
        if [ "${retries}" -le 0 ]; then
            echo "retries parameter must be a number greater than 0" >&2
            return 1
        fi
        ;;
    esac

    local delay=1
    local max_delay=60

    local remaining_tries="${retries}"

    # Try to run the command until it succeeds or we run out of retries
    while true; do
        # Check if set -e is set. If it is, toggle it off while running
        # the command, so we don't just exit straight away.
        if [[ "$-" =~ e ]]; then
            set +e
            eval "${cmd[*]}"
            local exit_code=$?
            set -e
        else
            # Set -e is not set, just run the command
            eval "${cmd[*]}"
            local exit_code=$?
        fi

        if [ "${exit_code}" -eq 0 ]; then
            return 0
        fi

        if [ "${remaining_tries}" -eq 0 ]; then
            # Return the exit code of the command
            echo "Command failed, giving up after $((retries + 1)) attempts..." >&2
            return ${exit_code}
        fi

        # Calculate the delay for the next iteration
        delay=$((delay * 2))
        if [ "${delay}" -gt "${max_delay}" ]; then
            delay=${max_delay}
        fi

        echo "Command failed, retrying in ${delay} seconds..." >&2
        sleep ${delay}

        remaining_tries=$((remaining_tries - 1))
    done
}

set -e

FOO=$(retry 2 false)

echo "${FOO}"