watch_files.sh

#!/usr/local/bin/bash
set -e

usage() {
cat << EOF
Usage: ./dev.sh [options...]
Options:
  -p, --pattern    Pattern of files to watch
  -s, --sleep      Time to wait between scans
  -c, --command    Command to run when changes are detected
  -h, --help       This help text
EOF
}

bash_version_check() {
    local bash_major_version=$(echo $BASH_VERSION | head -c 1)
    if [ $bash_major_version -lt 4 ]; then
        echo "This script requires associative arrays, which are supported in bash >= 4." >&2
        exit 1
    fi
}

assert_args() {
    if [ -z ${PATTERN+x} ]; then echo "Please provide a value for -p|--pattern." >&2; exit 1; fi
    if [ -z ${SLEEP_SECONDS+x} ]; then echo "Please provide a value for -s|--sleep." >&2; exit 1; fi
    if [ -z ${BUILD_COMMAND+x} ]; then echo "Please provide a value for -c|--command." >&2; exit 1; fi
}

scan_files() {
    for file in $(find . -name *.go); do
        local md5=$(md5 -q $file)
        local time_modified=$(GetFileInfo -d $file)

        # hash key name can't have periods or slashes
        file=${file//\./}
        file=${file//\//}

        if [ ! "${FILE_MD5S[$file]+_}" ]; then
            echo "[$time_modified]: new file: $file"
            FILE_MD5S[$file]=$md5
            build_project
            return
        fi

        if [ "${FILE_MD5S[$file]}" != "$md5" ]; then
            echo "[$time_modified]: file changed: $file"
            FILE_MD5S[$file]=$md5
            build_project
            return
        fi
    done
}

build_project() {
    $($BUILD_COMMAND)
    #godep go build
}

start_loop() {
    while true; do
        scan_files
        sleep $SLEEP_SECONDS
    done
}

bash_version_check

while [[ $# -gt 1 ]]; do
    key="$1"

    case $key in
        -p|--pattern)
            PATTERN="$2"
            shift
        ;;
        -s|--sleep)
            SLEEP_SECONDS="$2"
            shift
        ;;
        -c|--command)
            BUILD_COMMAND="$2"
            shift
        ;;
        -h|--help)
            usage
            exit 0
        ;;
        *)
            usage
            exit 1
        ;;
    esac
    shift
done

assert_args

cd "$(dirname "$0")"
declare -A FILE_MD5S

start_loop