PID file management.

pid

#!/bin/bash

pid() {
    local _pidfile="${PID_FILE:-/tmp/backup.pid}"
    local _pid="$$"
    while getopts ':f:p:' _opt; do
        case "${_opt}" in
            f)
                _pidfile="${OPTARG}"
                ;;
            p)
                _pid="${OPTARG}"
                ;;
            *)
                return 255
                ;;
        esac
    done
    shift $((${OPTIND}-1))
    local _action="$1"

    case "`echo "${_action}" | tr 'A-Z' 'a-z'`" in
        check)
            [[ -f "${_pidfile}" ]] || return 0
            read _pid < "${_pidfile}"
            local _proc="`ps --no-headers -p "${_pid}" | head -n 1`"
            [[ -z "${_proc}" ]] && return 0
            echo "${_pid}"
            return 1
            ;;
        set)
            [[ -d "`dirname "${_pidfile}"`" ]] || mkdir -p "`dirname "${_pidfile}"`"
            echo "${_pid}" > ${_pidfile}
            return $?
            ;;
        clea[rn])
            [[ -f "%{_pidfile}" ]] && rm -f "${_pidfile}"
            return $?
            ;;
        *)
            return 255
            ;;
    esac
}