What causes "Option %s: missing .env file path " in dotnet/runtime?

Supply the .env file path: 'corerun -e ./.env App.dll'.

Option %s: missing .env file path

Error message

Option %s: missing .env file path

What it means

Printed by parse_args() when -e / --env is the LAST token (i >= argc after i++). The option expects a path to a .env file whose variables corerun will load_into_current_process(). None follows. Parsing breaks and returns false.

Source

Thrown at src/coreclr/hosts/corerun/corerun.cpp:843

            {
                break;
            }
        }
        else if (pal::strcmp(option, W("d")) == 0 || (pal::strcmp(option, W("debug")) == 0))
        {
            config.wait_to_debug = true;
        }
        else if (pal::strcmp(option, W("st")) == 0)
        {
            config.self_test = true;
            return true;
        }
        else if (pal::strcmp(option, W("e")) == 0 || (pal::strcmp(option, W("env")) == 0))
        {
            i++;
            if (i >= argc)
            {
                pal::fprintf(stderr, W("Option %s: missing .env file path\n"), arg);
                break;
            }

            std::ifstream dotenvFile{ pal::convert_to_utf8(argv[i]) };
            config.dotenv_configuration = dotenv{ pal::string_t{ argv[i] }, dotenvFile};
        }
        else if ((pal::strcmp(option, W("?")) == 0 || (pal::strcmp(option, W("h")) == 0 || (pal::strcmp(option, W("help")) == 0))))
        {
            display_usage();
            break;
        }
        else
        {
            pal::fprintf(stderr, W("Unknown option %s\n"), arg);
            break;
        }
    }

View on GitHub (pinned to 290d5ab72c)

Solutions

Supply the .env file path: 'corerun -e ./.env App.dll'.
Ensure the file is readable; it is opened with std::ifstream in UTF-8.
Drop -e and export the variables directly in the shell if simpler.

Example fix

# before
corerun -e App.dll
# after
corerun -e ./config/.env App.dll

Defensive patterns

Strategy: validation

Validate before calling

# ensure -e/--env is never the trailing token
if [ "${@: -1}" = "-e" ] || [ "${@: -1}" = "--env" ]; then
  echo '-e requires a following .env file path'; exit 2
fi

Prevention

Always follow -e with a readable .env file path.
Prefer exporting variables in the shell if you only need a couple.
Confirm the file is UTF-8 (opened with std::ifstream).

When it happens

Trigger: User runs 'corerun -e' with no path after. The dotenv file is later loaded via config.dotenv_configuration.load_into_current_process() inside run().

Common situations: Forgotten .env path; trailing -e; meant to use shell 'source .env' instead.

Related errors

AI-assisted analysis of dotnet/runtime@290d5ab72c (2026-08-06). Data as JSON: /api/errors/f75f6269c6a6e4f0. Report an issue: GitHub.