denv

A fast, minimal direnv. Zero dependencies, single static Rust binary (378K stripped), direnv-compatible .envrc scripts.

direnv runs on every cd. It's an 8MB Go binary that has to initialize its runtime even when nothing changed. denv solves this by being small, doing as little work as possible on the noop path, and avoiding the subprocess entirely as much as possible in the hook.

Install

Download to ~/.local/bin/denv and add the hook for your shell:

Fish (~/.config/fish/config.fish):

denv hook fish | source

Bash (~/.bashrc):

eval "$(denv hook bash)"

Zsh (~/.zshrc):

eval "$(denv hook zsh)"

Usage

cd myproject
echo 'export SECRET=hunter2' > .envrc
denv allow    # trust and activate
# denv: +SECRET

cd ..
# denv: -SECRET

.env files load automatically (no trust needed). .envrc files are bash scripts and require denv allow since they execute code.

When both exist, .env is loaded after .envrc — .env wins on conflicts.

Commands

Command	Purpose
denv allow	Trust .envrc, activate
denv deny	Revoke trust, unload
denv reload	Force re-evaluate

How it works

On cd, the shell hook runs denv export <shell>. denv walks up from the current directory looking for .envrc or .env. If found and trusted, it spawns one bash subprocess to evaluate the script, diffs the environment before/after, and emits shell-appropriate commands (set -gx/export/unset) for the shell to source.

Per-shell state is tracked by PID so multiple terminals stay independent. When you leave a directory, previous values are restored exactly.

Editing .envrc changes its mtime, which invalidates trust until you re-run denv allow. This prevents stale or tampered scripts from running silently.

Noop fast path

The common case — cd'ing within a project where nothing changed — is heavily optimized:

• All shells: The hook checks __DENV_STATE and uses test -nt against a sentinel file to detect edits and deletions. If the directory matches and no files changed, it returns immediately — zero subprocesses, zero forks. direnv spawns the full binary unconditionally on every prompt.
• Binary (when the subprocess is needed): 378K stripped Rust with fat LTO, panic = "abort", zero runtime dependencies. direnv is 8MB of Go.

direnv compat

.envrc scripts can use common direnv stdlib functions: PATH_add, path_add, has, source_env, source_up, dotenv, strict_env, log_status, and others.

layout* and some nontrivial or specialized things are not supported. And of course, direnv-daemon specific stuff are not supported.