process.subr

# Copyright 2012 Google Inc.
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#
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# modification, are permitted provided that the following conditions are
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#
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shtk_import cleanup
shtk_import cli


shtk_process_run() {
    local timeout=
    local workdir=

    local OPTIND
    while getopts ':t:w:' arg "${@}"; do
        case "${arg}" in
            t)  # Timeout.
                timeout="${OPTARG}"
                ;;

            w)  # Work directory.
                workdir="${OPTARG}"
                ;;

            :)
                shtk_cli_error "Missing argument to option -${OPTARG} in" \
                    "shtk_process_run"
                ;;

            \?)
                shtk_cli_error "Unknown option -${OPTARG} in shtk_process_run"
                ;;
        esac
    done
    shift $((${OPTIND} - 1))
    OPTIND=1  # Should not be necessary due to the 'local' above.

    shtk_cli_info "Running '${@}' in $(pwd)"

    local ret=
    if [ -z "${timeout}" ]; then
        ret=0
        if [ "${workdir}" = . ]; then
            "${@}" || ret="${?}"
        else
            ( cd "${workdir}" && "${@}" ) || ret="${?}"
        fi
    else
        # Spawning a process with a timeout is tricky because we have to spawn
        # two subprocesses: one to run the actual process and one to act as a
        # watchdog.  Because both of these processes are blocking, we cannot
        # perform their duties on the current process.  These two processes kill
        # themselves mutually on completion regardless of the order in which
        # they finish and, because their interdependency, we need to pass
        # details between them with a file.  Once they are both dead, we have to
        # guess what actually happened.
        #
        # The cookie file below works like this: first, the PID of the
        # subprocess running the desired command is written to it.  The watchdog
        # process uses the content of this file to kill the subprocess if
        # needed.  Once the subprocess has finished, its exit status is written
        # to the cookie.  If the subprocess has been killed, then the magic word
        # TIMEOUT is written to the cookie.

        local pattern="${TMPDIR:-/tmp}/shtk.XXXXXX"
        local cookie="$(mktemp "${pattern}" 2>/dev/null)"
        [ -f "${cookie}" ] || shtk_cli_error "Failed to create temporary file" \
            "using pattern ${pattern}"
        eval "shtk_process_run_remove_cookie() { rm -f '${cookie}'; }"
        shtk_cleanup_register shtk_process_run_remove_cookie

        (
            sleep "${timeout}"
            while [ -z "$(cat "${cookie}")" ]; do
                # Race protection: the process has not yet started.
                sleep 1
            done
            local pid="$(cat "${cookie}")"
            shtk_cli_warning "Timer expired; killing ${pid}"
            kill -9 "${pid}"
            echo "TIMEOUT" >"${cookie}"
        ) &
        local watchdog="${!}"

        (
            local ret=0
            if [ "${workdir}" = . ]; then
                "${@}" || ret="${?}"
            else
                ( cd "${workdir}" && "${@}" ) || ret="${?}"
            fi
            kill -9 "${watchdog}"
            while [ -z "$(cat "${cookie}")" ]; do
                # Race protection: the parent has not yet written the cookie.
                sleep 1
            done
            echo "${ret}" >"${cookie}"
        ) &
        local subprocess="${!}"
        echo "${subprocess}" >"${cookie}"

        wait >/dev/null 2>&1  # Silence 'Killed' notifications.

        ret="$(cat "${cookie}")"
        rm -f "${cookie}"
    fi
    [ -n "${ret}" ] || shtk_cli_error "ret not initialized; something failed"

    if [ "${ret}" = "TIMEOUT" ]; then
        shtk_cli_warning "Command timed out after ${timeout} seconds"
        ret=127
    elif [ "${ret}" -eq 0 ]; then
        shtk_cli_info "Command finished successfully"
    else
        shtk_cli_warning "Command failed with code ${ret}"
    fi
    return "${ret}"
}