lfe_init.erl - Runtime Initialization

Purpose: Initialize LFE runtime environment when starting Erlang with LFE as the default shell.

Location: src/lfe_init.erl Size: 118 LOC, 4.1KB

Module Classification: Runtime infrastructure, launcher

Public API

start() -> ok

Entry point for -user lfe_init. Located at lfe_init.erl:49-74.

Startup Modes

Interactive Shell:

erl -user lfe_init

Starts LFE REPL as default shell.

Eval Mode:

erl -user lfe_init -e "(+ 1 2)"

Evaluates expression and exits.

Script Mode:

erl -user lfe_init script.lfe arg1 arg2

Runs script with arguments.

Implementation

Main Entry (start/0 at lines 49-74):

start() ->
    OTPRelease = erlang:system_info(otp_release),
    Repl = case init:get_argument(repl) of
        {ok, [[R|_]]} -> list_to_atom(R);
        _Other -> ?DEFAULT_REPL  % lfe_shell
    end,
    case collect_args(init:get_plain_arguments()) of
        {[],[]} ->
            % Start interactive shell
            if OTPRelease >= "26" ->
                user_drv:start(#{initial_shell => {Repl,start,[]}});
               true ->
                user_drv:start(['tty_sl -c -e',{Repl,start,[]}])
            end;
        {Evals,Script} ->
            % Run evals and/or script
            if OTPRelease >= "26" ->
                user_drv:start(#{initial_shell => noshell});
               true ->
                user:start()
            end,
            run_evals_script(Repl, Evals, Script)
    end.

OTP Version Handling:

OTP 26 changed user_drv API:

OTP <26: user_drv:start(['tty_sl -c -e', {Repl,start,[]}])
OTP ≥26: user_drv:start(#{initial_shell => {Repl,start,[]}})

Argument Collection (collect_args/1 at lines 76-86):

collect_args(Args) ->
    {Evals, Rest} = collect_evals(Args, []),
    {Evals, Rest}.

collect_evals(["-e", Eval|Args], Evals) ->
    collect_evals(Args, [Eval|Evals]);
collect_evals(["-lfe_eval", Eval|Args], Evals) ->
    collect_evals(Args, [Eval|Evals]);
collect_evals(Args, Evals) ->
    {lists:reverse(Evals), Args}.

Script Execution (run_evals_script/3 at lines 88-97):

run_evals_script(Repl, Evals, Script) ->
    Run = fun () ->
        St = Repl:run_strings(Evals),  % Run eval strings
        case Script of
            [F|As] -> Repl:run_script(F, As, St);
            [] -> {[],St}
        end
    end,
    spawn_link(fun () -> run_script(Repl, Run) end).

Error Handling (run_script/2 at lines 102-118):

run_script(_Repl, Run) ->
    try
        Run(),
        timer:sleep(1),
        init:stop(?OK_STATUS)  % Exit 0
    catch
        ?CATCH(Class, Error, Stack)
            Skip = fun (M, _F, _A) -> M =/= lfe_eval end,
            Format = fun (T, I) -> lfe_io:prettyprint1(T, 15, I, 80) end,
            Cs = lfe_error:format_exception(Class, Error, Stack,
                                            Skip, Format, 1),
            io:put_chars(Cs),
            halt(?ERROR_STATUS)  % Exit 127
    end.

Exit Codes: