A Bash command to keep trying running a command until it succeeds or is canceled.

keeptrying

#!/usr/bin/env bash

set -eu

COLOR_ERROR='\033[0;31m'
COLOR_RESET='\e[0m'

prog_name="$(basename "$0")"

function usage() {
    if [[ ${1:-} = '--with-desc' ]]
    then
        >&2 echo 'Run a given command until it succeeds or is cancelled.'
    fi

    >&2 cat <<USG
Usage:
    ${prog_name} [-d|--debug] [-c|--clear] [-e|--redirect-stderr DEST] [-b|--backoff BACKOFF] [--] COMMAND ARGS
USG
    exit
}

function unexpected_arg() {
    >&2 echo -e "${COLOR_ERROR}Error: unexpected argument '$1'.${COLOR_RESET}"
    usage
}

backoff=1s
debug_mode=off
clear_mode=off
cmd_stderr=/dev/stderr

while [[ $# -gt 0 ]]
do
    case "$1" in
        -h|--help)
            usage --with-desc
            ;;
        -b|--backoff)
            shift # flag
            backoff="${1:-}"
            shift # value
            ;;
        -c|--clear)
            shift # flag
            clear_mode=on
            ;;
        -d|--debug)
            shift # flag
            debug_mode=on
            ;;
        -e|--redirect-stderr)
            shift # flag
            cmd_stderr="${1:-}"
            shift # value
            ;;
        --)
            shift
            break
            ;;
        -*)
            unexpected_arg "$1"
            ;;
        *)
            break
            ;;
    esac
done

debug() {
    if [[ $debug_mode = on ]]
    then
        >&2 echo "$@"
    fi
}

cmd="${1:-}"
if [[ $cmd = '' ]]
then
    >&2 echo -e "${COLOR_ERROR}Error: no command provided.${COLOR_RESET}"
    usage
fi
shift

EXIT_SUCCESS=0
EXIT_CMD_NOT_FOUND=127
EXIT_CANCEL=130

while true
do
    if [[ $clear_mode = on ]]
    then
        clear
    fi

    debug "Running command:" "$cmd" "$@"
    set +e
    "$cmd" "$@" 2> "$cmd_stderr"
    exit_code=$?
    set -e
    debug -n "Command exited with: $exit_code."

    if [[ $exit_code = $EXIT_SUCCESS || $exit_code = $EXIT_CMD_NOT_FOUND || $exit_code = $EXIT_CANCEL ]]
    then
        debug ''
        exit $exit_code
    fi

    debug " Waiting $backoff before retry…"
    sleep "$backoff"
done