Bash script to retry a failed command

retry.sh

#!/bin/bash

# Retries a command on failure.

HELP=\
"$0: $0 [flags] [options] [--] COMMAND
    Runs a command, retrying if the command fails

    Arguments:
      COMMAND                    The command to run

    Flags:
      -h, --help                 Display this message and exit
      --forever                  Retry until the command succeeds

    Options:
      -n, --num-attempts number  The maximum number of times to retry the command (default: 10)
      -d, --delay number         The number of seconds to wait between attempts (default: 3)"

sleep_duration=3
num_attempts=10
params=""
forever=""

while (( "$#" ));
do
    case "$1" in
        -h|--help)
            echo "$HELP"
            exit 0
            ;;
        --forever)
            forever=true
            shift
            ;;
        -d|--delay)
            sleep_duration="$2"
            shift 2
            ;;
        -n|--num-attempts)
            num_attempts="$2"
            shift 2
            ;;
        --)
            shift 1
            params="$params $@"
            break
            ;;
        *)
            params="$params $1"
            shift
            ;;
    esac
done

eval set -- "$params"

retry () {
    local -r -i max_attempts="$1"; shift
    local -r cmd="$@"
    local -i attempt_num=1

    until $cmd
    do
        attempt_str="$attempt_num/$max_attempts"
        if [ "$forever" = true ];
        then
            attempt_str="$attempt_num"
        fi
        if (( attempt_num == max_attempts )) && [ "$forever" != true ];
        then
            echo "Attempt $attempt_str failed. Giving up."
            return 1
        else
            echo "Attempt $attempt_str failed. Retrying in $sleep_duration seconds..."
            ((attempt_num++))
            sleep "$sleep_duration"
        fi
    done
}

retry "$num_attempts" "$@"