Rust rewrite.

The Python version was taking hundreds of millis for a small number of
env vars on my machine - enough that starting a new shell was a bit
itchy. The compiled version, even in debug mode, is ~10x faster.

16 files changed, 495 insertions, 295 deletions

diff --git a/.envrc b/.envrc
deleted file mode 100644
index 1caca09..0000000
--- a/.envrc
+++ /dev/null
@@ -1,5 +0,0 @@
-if has pyenv; then
-    pyenv install --skip-existing
-fi
-
-layout python3
diff --git a/.gitignore b/.gitignore
index a1b52c5..162885f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,21 +1,2 @@
-# If you're using direnv, the .envrc file will generate .direnv automatically
-# when loaded.
-/.direnv/
-
-# Generated metadata created by `pip install`, `python setup.py sdist`, and
-# friends. Will be reconstituted from setup.py as needed.
-*.egg-info
-
-# Compiled Python bytecode. Will be regenerated on import, for the current
-# Python version.
-*.pyc
-
-# Dependencies installed via setup_requires; will be recreated from setuptools
-# as needed.
-/.eggs/
-
-# Intermediate build artifacts generated by `python setup.py sdist`.
-/build/
-
-# Final outputs generated by `python setup.py bdist`.
-/dist/
+# Cargo build output, recreated by any Cargo command.
+/target/
diff --git a/.pylintrc b/.pylintrc
deleted file mode 100644
index c590644..0000000
--- a/.pylintrc
+++ /dev/null
@@ -1,16 +0,0 @@
-[MASTER]
-# No lint failures allowed.
-fail-under=10.0
-
-# Prevent litter in ~/.pylint.d
-persistent=no
-
-[MESSAGES CONTROL]
-disable=
-      # None of the modules in this are designed for import. This is a tool,
-      # with no library attached.
-      missing-module-docstring,
-      # I fundamentally disagree with pylint's assertion that stdlib imports go
-      # before library imports. All libraries are created more or less equal;
-      # the stdlib merely happens to come with the language.
-      wrong-import-order,
diff --git a/.python-version b/.python-version
deleted file mode 100644
index a5c4c76..0000000
--- a/.python-version
+++ /dev/null
@@ -1 +0,0 @@
-3.9.0
diff --git a/Cargo.lock b/Cargo.lock
new file mode 100644
index 0000000..26dcf56
--- /dev/null
+++ b/Cargo.lock
@@ -0,0 +1,282 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
+name = "atty"
+version = "0.2.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d9b39be18770d11421cdb1b9947a45dd3f37e93092cbf377614828a319d5fee8"
+dependencies = [
+ "hermit-abi",
+ "libc",
+ "winapi",
+]
+
+[[package]]
+name = "autocfg"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cdb031dd78e28731d87d56cc8ffef4a8f36ca26c38fe2de700543e627f8a464a"
+
+[[package]]
+name = "bitflags"
+version = "1.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cf1de2fe8c75bc145a2f577add951f8134889b4795d47466a54a5c846d691693"
+
+[[package]]
+name = "clap"
+version = "3.0.0-beta.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4bd1061998a501ee7d4b6d449020df3266ca3124b941ec56cf2005c3779ca142"
+dependencies = [
+ "atty",
+ "bitflags",
+ "clap_derive",
+ "indexmap",
+ "lazy_static",
+ "os_str_bytes",
+ "strsim",
+ "termcolor",
+ "textwrap",
+ "unicode-width",
+ "vec_map",
+]
+
+[[package]]
+name = "clap_derive"
+version = "3.0.0-beta.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "370f715b81112975b1b69db93e0b56ea4cd4e5002ac43b2da8474106a54096a1"
+dependencies = [
+ "heck",
+ "proc-macro-error",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "envdir-helper"
+version = "0.2.0"
+dependencies = [
+ "clap",
+ "libc",
+ "shlex",
+ "thiserror",
+]
+
+[[package]]
+name = "hashbrown"
+version = "0.9.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d7afe4a420e3fe79967a00898cc1f4db7c8a49a9333a29f8a4bd76a253d5cd04"
+
+[[package]]
+name = "heck"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "87cbf45460356b7deeb5e3415b5563308c0a9b057c85e12b06ad551f98d0a6ac"
+dependencies = [
+ "unicode-segmentation",
+]
+
+[[package]]
+name = "hermit-abi"
+version = "0.1.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5aca5565f760fb5b220e499d72710ed156fdb74e631659e99377d9ebfbd13ae8"
+dependencies = [
+ "libc",
+]
+
+[[package]]
+name = "indexmap"
+version = "1.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4fb1fa934250de4de8aef298d81c729a7d33d8c239daa3a7575e6b92bfc7313b"
+dependencies = [
+ "autocfg",
+ "hashbrown",
+]
+
+[[package]]
+name = "lazy_static"
+version = "1.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
+
+[[package]]
+name = "libc"
+version = "0.2.81"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1482821306169ec4d07f6aca392a4681f66c75c9918aa49641a2595db64053cb"
+
+[[package]]
+name = "os_str_bytes"
+version = "2.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "afb2e1c3ee07430c2cf76151675e583e0f19985fa6efae47d6848a3e2c824f85"
+
+[[package]]
+name = "proc-macro-error"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "da25490ff9892aab3fcf7c36f08cfb902dd3e71ca0f9f9517bea02a73a5ce38c"
+dependencies = [
+ "proc-macro-error-attr",
+ "proc-macro2",
+ "quote",
+ "syn",
+ "version_check",
+]
+
+[[package]]
+name = "proc-macro-error-attr"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a1be40180e52ecc98ad80b184934baf3d0d29f979574e439af5a55274b35f869"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "version_check",
+]
+
+[[package]]
+name = "proc-macro2"
+version = "1.0.24"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1e0704ee1a7e00d7bb417d0770ea303c1bccbabf0ef1667dae92b5967f5f8a71"
+dependencies = [
+ "unicode-xid",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "991431c3519a3f36861882da93630ce66b52918dcf1b8e2fd66b397fc96f28df"
+dependencies = [
+ "proc-macro2",
+]
+
+[[package]]
+name = "shlex"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7fdf1b9db47230893d76faad238fd6097fd6d6a9245cd7a4d90dbd639536bbd2"
+
+[[package]]
+name = "strsim"
+version = "0.10.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "73473c0e59e6d5812c5dfe2a064a6444949f089e20eec9a2e5506596494e4623"
+
+[[package]]
+name = "syn"
+version = "1.0.55"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a571a711dddd09019ccc628e1b17fe87c59b09d513c06c026877aa708334f37a"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-xid",
+]
+
+[[package]]
+name = "termcolor"
+version = "1.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2dfed899f0eb03f32ee8c6a0aabdb8a7949659e3466561fc0adf54e26d88c5f4"
+dependencies = [
+ "winapi-util",
+]
+
+[[package]]
+name = "textwrap"
+version = "0.12.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "203008d98caf094106cfaba70acfed15e18ed3ddb7d94e49baec153a2b462789"
+dependencies = [
+ "unicode-width",
+]
+
+[[package]]
+name = "thiserror"
+version = "1.0.22"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0e9ae34b84616eedaaf1e9dd6026dbe00dcafa92aa0c8077cb69df1fcfe5e53e"
+dependencies = [
+ "thiserror-impl",
+]
+
+[[package]]
+name = "thiserror-impl"
+version = "1.0.22"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9ba20f23e85b10754cd195504aebf6a27e2e6cbe28c17778a0c930724628dd56"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "unicode-segmentation"
+version = "1.7.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bb0d2e7be6ae3a5fa87eed5fb451aff96f2573d2694942e40543ae0bbe19c796"
+
+[[package]]
+name = "unicode-width"
+version = "0.1.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9337591893a19b88d8d87f2cec1e73fad5cdfd10e5a6f349f498ad6ea2ffb1e3"
+
+[[package]]
+name = "unicode-xid"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f7fe0bb3479651439c9112f72b6c505038574c9fbb575ed1bf3b797fa39dd564"
+
+[[package]]
+name = "vec_map"
+version = "0.8.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f1bddf1187be692e79c5ffeab891132dfb0f236ed36a43c7ed39f1165ee20191"
+
+[[package]]
+name = "version_check"
+version = "0.9.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b5a972e5669d67ba988ce3dc826706fb0a8b01471c088cb0b6110b805cc36aed"
+
+[[package]]
+name = "winapi"
+version = "0.3.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5c839a674fcd7a98952e593242ea400abe93992746761e38641405d28b00f419"
+dependencies = [
+ "winapi-i686-pc-windows-gnu",
+ "winapi-x86_64-pc-windows-gnu",
+]
+
+[[package]]
+name = "winapi-i686-pc-windows-gnu"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
+
+[[package]]
+name = "winapi-util"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "70ec6ce85bb158151cae5e5c87f95a8e97d2c0c4b001223f33a334e3ce5de178"
+dependencies = [
+ "winapi",
+]
+
+[[package]]
+name = "winapi-x86_64-pc-windows-gnu"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "712e227841d057c1ee1cd2fb22fa7e5a5461ae8e48fa2ca79ec42cfc1931183f"
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..e266d8c
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,11 @@
+[package]
+name = "envdir-helper"
+version = "0.2.0"
+authors = ["Owen Jacobson <owen@grimoire.ca>"]
+edition = "2018"
+
+[dependencies]
+clap = "~3.0.0-beta.2"
+libc = "~0.2.40"
+shlex = "~0.1.1"
+thiserror = "~1.0"
diff --git a/README.md b/README.md
index f5f4439..63f46b5 100644
--- a/README.md
+++ b/README.md
@@ -13,8 +13,9 @@ I've replaced all of that with a single line:
     eval "$(envdir-helper)"
 
 This program also supports setting non-exported shell variables, using the
-`--no-export` flag. This is useful for prompts and other shell configuration
-that should not be propagated through to subshells and other programs. This behaviour is the default if the env directory's name ends in `rc`:
+`--export false` flag. This is useful for prompts and other shell configuration
+that should not be propagated through to subshells and other programs. This
+behaviour is the default if the env directory's name ends in `rc`:
 
     eval "$(envdir-helper .envdir.rc)"
 
@@ -37,18 +38,6 @@ This program does relatively little to manage this directly. One approach that h
 
 ## Installation
 
-Some familiarity with Python is assumed, here:
+Some familiarity with Rust is assumed, here:
 
-* Make a virtual environment;
-* `$VIRTUALENV/bin/pip install git+https://github.com/ojacobson/envdir-helper/#egg=envdir-helper`; and
-* Add its `bin` directory to `PATH` by other means, or invoke it by full path.
-
-## Development
-
-I use [pyenv] and [`direnv`] to manage development. The configuration in
-`.envrc` will automatically create a virtual Python environment using Pyenv (if
-possible) or your current Python version (otherwise), and load it, once the
-configuration is allowed. See the `direnv` documentation and the included
-`.envrc` script for details.
-
-[pyenv]: https://github.com/pyenv/pyenv
+* `cargo install --git https://github.com/ojacobson/envdir-helper`
diff --git a/dev-requirements.in b/dev-requirements.in
deleted file mode 100644
index 60ced2c..0000000
--- a/dev-requirements.in
+++ /dev/null
@@ -1,3 +0,0 @@
-black
-pylint
-pip-tools
diff --git a/dev-requirements.txt b/dev-requirements.txt
deleted file mode 100644
index a8f9e72..0000000
--- a/dev-requirements.txt
+++ /dev/null
@@ -1,26 +0,0 @@
-#
-# This file is autogenerated by pip-compile
-# To update, run:
-#
-#    pip-compile dev-requirements.in
-#
-appdirs==1.4.4            # via black
-astroid==2.4.2            # via pylint
-black==20.8b1             # via -r dev-requirements.in
-click==7.1.2              # via black, pip-tools
-isort==5.6.4              # via pylint
-lazy-object-proxy==1.4.3  # via astroid
-mccabe==0.6.1             # via pylint
-mypy-extensions==0.4.3    # via black
-pathspec==0.8.1           # via black
-pip-tools==5.4.0          # via -r dev-requirements.in
-pylint==2.6.0             # via -r dev-requirements.in
-regex==2020.11.13         # via black
-six==1.15.0               # via astroid, pip-tools
-toml==0.10.2              # via black, pylint
-typed-ast==1.4.1          # via black
-typing-extensions==3.7.4.3  # via black
-wrapt==1.12.1             # via astroid
-
-# The following packages are considered to be unsafe in a requirements file:
-# pip
diff --git a/envdir/__init__.py b/envdir/__init__.py
deleted file mode 100644
index a7b85bd..0000000
--- a/envdir/__init__.py
+++ /dev/null
@@ -1,7 +0,0 @@
-from importlib.metadata import version, PackageNotFoundError
-
-try:
-    __version__ = version("envdir-helper")
-except PackageNotFoundError:
-    # package is not installed
-    pass
diff --git a/envdir/cli.py b/envdir/cli.py
deleted file mode 100644
index 9a06baf..0000000
--- a/envdir/cli.py
+++ /dev/null
@@ -1,145 +0,0 @@
-import click
-import os
-import os.path as op
-import pathlib
-import shlex
-import stat
-import subprocess as sp
-
-
-@click.command()
-@click.pass_context
-@click.version_option()
-@click.option(
-    "--export/--no-export",
-    default=None,
-    help="Export generated environment variables [default: --export]",
-)
-@click.argument(
-    "envdir",
-    default=str(pathlib.Path.home() / ".envdir"),
-    metavar="DIR",
-)
-def main(context, export, envdir):
-    r"""Load environment variables from DIR (or ~/.envdir).
-
-    For each non-directory entry in DIR, this will output a brief shell script
-    to set an environment with the same name. If the entry is an executable
-    program, it will be run (with the current environment) and its output will
-    be used as the value of the environment variable. Otherwise, it will be
-    read, and its content will be used. In either case, a single trailing
-    newline will be removed, if present.
-
-    This process skips any file which can't be run or read, as appropriate, and
-    outputs a warning on stderr.
-
-    The intended use case for this is in shell profiles, in the form:
-
-        eval "$(envdir-helper)"
-
-    The generated output is compatible with sh, and thus with bash and zsh.
-    """
-
-    def warn_on_skipped(path, reason):
-        """Log any skipped paths to stderr."""
-        stderr = click.get_text_stream("stderr")
-        click.echo(f"{context.info_name}: skipping {path}: {reason}", file=stderr)
-
-    if export is None:
-        env_script = detect_env_script(
-            envdir, rc=no_export_env_script, default=export_env_script
-        )
-    elif export:
-        env_script = export_env_script
-    else:
-        env_script = no_export_env_script
-
-    for name, content in walk_entries(envdir, on_skipped=warn_on_skipped):
-        script = env_script(name, content)
-        click.echo(script)
-
-
-def detect_env_script(path, rc, default):  # pylint: disable=invalid-name
-    """Detect which of two values to use based on whether `path` ends with
-    `"rc"`. If it does, returns `rc`; otherwise, returns `default`.
-    """
-    if path.endswith("rc"):
-        return rc
-    return default
-
-
-def export_env_script(name, content):
-    """Given a name and contents, generate a shell script that will set and
-    export the corresponding environment variable, with that content."""
-    # use sh-friendly syntax here: don't assume `export` can have assignment
-    # side effects, so don't use `export FOO=BAR`. `FOO=BAR; export FOO` is
-    # portable to all posix shells.
-    qname = shlex.quote(name)
-    qcontent = shlex.quote(content)
-    return f"{qname}={qcontent}; export {qname}"
-
-
-def no_export_env_script(name, content):
-    """Given a name and contents, generate a shell script that will set and NOT
-    export the corresponding environment variable, with that content."""
-    qname = shlex.quote(name)
-    qcontent = shlex.quote(content)
-    return f"{qname}={qcontent}"
-
-
-def walk_entries(envdir, on_skipped):
-    """Yields a name, value pair for each environment file in envdir.
-
-    The path for any skipped items (generally, failing or unrunnable programs,
-    or unreadable files) will be passed to the `on_skipped` callback, along with
-    the exception that caused it to be skipped.
-    """
-    for name in sorted(os.listdir(envdir)):
-        path = op.join(envdir, name)
-        try:
-            path_stat = os.stat(path)
-            if directory(path_stat):
-                continue
-
-            if executable(path_stat):
-                content = from_program(path)
-            else:
-                content = from_file(path)
-        except Exception as reason:  # pylint: disable=broad-except
-            on_skipped(path, reason)
-            continue
-        if content.endswith("\n"):
-            content = content[:-1]
-        yield name, content
-
-
-def directory(item):
-    """True iff item is a stat_result representing a directory."""
-    return stat.S_ISDIR(item.st_mode)
-
-
-def executable(item):
-    """True iff item is a stat_result representing something executable.
-
-    This doesn't distinguish between dirs and files; both are considered
-    executable if any +x bit is set.
-    """
-    mode = stat.S_IMODE(item.st_mode)
-    mask = stat.S_IXUSR | stat.S_IXGRP | stat.S_IXOTH
-    return mode & mask != 0
-
-
-def from_program(path):
-    """Reads a program's complete stdout into a string."""
-    result = sp.run(
-        [path],
-        check=True,
-        stdout=sp.PIPE,
-    )
-    return result.stdout.decode("UTF-8")
-
-
-def from_file(path):
-    """Reads a file's complete content into a string."""
-    with open(path, "r") as file:
-        return file.read()
diff --git a/setup.py b/setup.py
deleted file mode 100644
index 8b2b5af..0000000
--- a/setup.py
+++ /dev/null
@@ -1,25 +0,0 @@
-from setuptools import setup, find_packages
-
-setup(
-    name="envdir-helper",
-    use_scm_version=True,
-
-    author="Owen Jacobson",
-    author_email="owen@grimoire.ca",
-
-    packages=find_packages(),
-
-    setup_requires=[
-        "setuptools_scm ~= 4.1",
-    ],
-
-    install_requires=[
-        "click ~= 7.1.0",
-    ],
-
-    entry_points={
-        "console_scripts": [
-            "envdir-helper=envdir.cli:main",
-        ],
-    },
-)
diff --git a/src/main.rs b/src/main.rs
new file mode 100644
index 0000000..df34235
--- /dev/null
+++ b/src/main.rs
@@ -0,0 +1,195 @@
+use std::env;
+use std::ffi::OsString;
+use std::fmt::Debug;
+use std::fs::{DirEntry, metadata, read_dir, read_to_string};
+use std::io;
+use std::path::{Path, PathBuf};
+use std::process::{Command, Stdio, ExitStatus};
+use std::string::FromUtf8Error;
+
+use clap::Clap;
+use thiserror::Error;
+
+/// Load environment variables from DIR (or ~/.envdir).
+///
+/// For each non-directory entry in DIR, this will output a brief shell script
+/// to set an environment variable with the same name. If the entry is an
+/// executable program, it will be run (with the current environment) and its
+/// output will be used as the value of the environment variable. Otherwise, it
+/// will be read, and its content will be used. In either case, a single
+/// trailing newline will be removed, if present.
+///
+/// This process skips any file which can't be run or read, as appropriate, and
+/// outputs a warning on stderr.
+///
+/// The intended use case for this is in shell profiles, in the form:
+///
+///     eval "$(envdir-helper)"
+///
+/// The generated output is compatible with sh, and thus with bash and zsh.
+#[derive(Clap)]
+#[clap(version=env!("CARGO_PKG_VERSION"))]
+struct Opts {
+    /// Directory to read environment variables from [default: ~/.envdir]
+    envdir: Option<PathBuf>,
+    /// Export generated environment variables [default: true]
+    #[clap(long)]
+    export: Option<bool>,
+}
+
+#[derive(Error, Debug)]
+enum EnvdirError {
+    #[error("failed to locate default envdir")]
+    NoDefaultEnvdir(#[from] DefaultDirError),
+    #[error("failed to read envdir directory")]
+    EnvdirListFailed(#[from] io::Error),
+    #[error("failed to decode a filename")]
+    PathStringError(#[from] PathStringError),
+}
+
+const SELF: &str = env!("CARGO_BIN_NAME");
+
+fn main() -> Result<(), EnvdirError> {
+    let opts: Opts = Opts::parse();
+
+    let envdir = match opts.envdir {
+        None => default_envdir()?,
+        Some(envdir) => envdir,
+    };
+
+    let output_fn = match opts.export {
+        None => detect_env_script(&envdir)?,
+        Some(true) => export_env_script,
+        Some(false) => no_export_env_script,
+    };
+
+    for path in read_dir(envdir)?
+        .filter_map(skip_failing_direntry)
+        .map(|entry| entry.path())
+        .filter(|path| !path.is_dir())
+    {
+        let name = path_to_string(&path)?;
+        match env_content(&path) {
+            Ok(content) => println!("{}", output_fn(name, &content)),
+            Err(e) => eprintln!("{}: error reading env value for {:?}: {:?}", SELF, name, e),
+        };
+    }
+
+    Ok(())
+}
+
+fn skip_failing_direntry<E: Debug>(result: Result<DirEntry, E>) -> Option<DirEntry> {
+    match result {
+        Ok(direntry) => Some(direntry),
+        Err(e) => {
+            eprintln!("{}: error reading envdir: {:?}", SELF, e);
+            None
+        }
+    }
+}
+
+#[derive(Error, Debug)]
+#[error("a required environment variable was not set")]
+struct DefaultDirError(#[from] env::VarError);
+
+fn default_envdir() -> Result<PathBuf, DefaultDirError> {
+    let mut envdir = PathBuf::from(env::var("HOME")?);
+    envdir.push(".envdir");
+
+    Ok(envdir)
+}
+
+type ExportScript = fn(&str, &str) -> String;
+
+fn detect_env_script(path: &Path) -> Result<ExportScript, PathStringError> {
+    let file_name = path_to_string(path)?;
+    Ok(if file_name.ends_with("rc") {
+        no_export_env_script
+    } else {
+        export_env_script
+    })
+}
+
+fn no_export_env_script(name: &str, content: &str) -> String {
+    let name = shlex::quote(name);
+    let content= shlex::quote(content);
+    format!("{}={}", name, content)
+}
+
+fn export_env_script(name: &str, content: &str) -> String {
+    let name = shlex::quote(name);
+    let content= shlex::quote(content);
+    format!("{}={}; export {}", name, content, name)
+}
+
+#[derive(Error, Debug)]
+enum PathStringError {
+    #[error("path has no name: {0}")]
+    NamelessPath(PathBuf),
+    #[error("path has a non-unicode name: {0:?}")]
+    NonUnicodePath(OsString),
+}
+
+fn path_to_string(path: &Path) -> Result<&str, PathStringError> {
+    use PathStringError::*;
+    let file_name = path.file_name()
+        .ok_or_else(|| NamelessPath(path.into()))?;
+    file_name.to_str()
+        .ok_or_else(|| NonUnicodePath(file_name.into()))
+}
+
+#[derive(Error, Debug)]
+enum EnvContentError {
+    #[error("io error: {0}")]
+    IoError(#[from] io::Error),
+    #[error("program produced non-UTF-8 output: {0}")]
+    NonUnicodeOutput(#[from] FromUtf8Error),
+    #[error("program {0:?} exited with status: {1}")]
+    ProgramFailed(PathBuf, ExitStatus)
+}
+
+fn env_content(path: &Path) -> Result<String, EnvContentError> {
+    let mut content = if is_program(path)? {
+        env_program_content(path)?
+    } else {
+        env_file_content(path)?
+    };
+
+    if content.ends_with("\n") {
+        content.pop();
+    }
+    
+    Ok(content)
+}
+
+fn is_program(path: &Path) -> io::Result<bool> {
+    const EXEC_MASK: u32 = (libc::S_IXUSR | libc::S_IXGRP | libc::S_IXOTH) as u32;
+
+    use std::os::unix::fs::PermissionsExt;
+
+    let metadata = metadata(path)?;
+    let permissions = metadata.permissions();
+
+    Ok(permissions.mode() & EXEC_MASK != 0)
+}
+
+fn env_program_content(path: &Path) -> Result<String, EnvContentError> {
+    use EnvContentError::*;
+
+    let output = Command::new(path)
+        .stdin(Stdio::piped())
+        .stdout(Stdio::piped())
+        .stderr(Stdio::inherit())
+        .output()?;
+    
+    if output.status.success() {
+        let output = String::from_utf8(output.stdout)?;
+        Ok(output)
+    } else {
+        Err(ProgramFailed(path.to_path_buf(), output.status))
+    }
+}
+
+fn env_file_content(path: &Path) -> Result<String, EnvContentError> {
+    Ok(read_to_string(path)?)
+}
diff --git a/tools/check b/tools/check
deleted file mode 100755
index 269a23d..0000000
--- a/tools/check
+++ /dev/null
@@ -1,10 +0,0 @@
-#!/bin/bash -e
-
-cd "$(dirname "$0")/.."
-
-## tools/check
-##
-## Run checks on the project, exiting with a zero status if all checks pass.
-
-tools/check-lint
-tools/check-style
diff --git a/tools/check-lint b/tools/check-lint
deleted file mode 100755
index eaebdf0..0000000
--- a/tools/check-lint
+++ /dev/null
@@ -1,10 +0,0 @@
-#!/bin/bash -e
-
-cd "$(dirname "$0")/.."
-
-## tools/check-lint
-##
-## Run lint checks on the project, exiting with a zero status if there are no lint
-## issues.
-
-exec pylint envdir
diff --git a/tools/check-style b/tools/check-style
deleted file mode 100755
index adb2499..0000000
--- a/tools/check-style
+++ /dev/null
@@ -1,10 +0,0 @@
-#!/bin/bash -e
-
-cd "$(dirname "$0")/.."
-
-## tools/check-style
-##
-## Run style checks on the project, exiting with a zero status if there are no style
-## issues.
-
-exec black --check --diff envdir