self-exe#

The absolute path of the currently running executable, cross-platform.

There is no portable way to ask "where is my own binary?": each operating system needs its own mechanism, and one (OpenBSD) cannot answer it reliably at all. self-exe wraps them behind a single call, canonicalised to an absolute, symlink-resolved path. It is the OCaml counterpart of Rust's std::env::current_exe, Go's os.Executable, and the C single-header whereami.

Sys.executable_name does not cover this: it is derived from argv[0] and is unreliable on macOS and under unusual invocation. Reach for self-exe when a program re-execs itself (on-demand daemons, privilege-separated workers), needs to find its install directory (sibling binaries, bundled data), or must be relocatable.

Installation#

$ opam install self-exe

If opam cannot find the package, it may not yet be released in the public opam-repository. Add the overlay repository, then install it:

$ opam repo add samoht https://tangled.org/gazagnaire.org/opam-overlay.git
$ opam update
$ opam install self-exe

Usage#

(* Re-exec ourselves, or locate a sibling tool installed next to us. *)
let me = Self_exe.path ()
let helper = Filename.concat (Self_exe.dir ()) "worker"

(* [path_opt] tells a guess from an authoritative answer. *)
let trustworthy = Self_exe.path_opt () <> None

path always returns a string -- best-effort, which is what re-exec callers want. path_opt is the strict variant: it is Some p only when the OS reported the path authoritatively, and None when only the argv[0] fallback was available.

Platform support#

The fallback resolves Sys.argv.(0) the way the launching shell would: a path is taken relative to the current directory, a bare name is searched along $PATH. It can be wrong if the cwd or $PATH changed since launch, or if the binary was moved -- use path_opt when you must know the answer is reliable.

License#

ISC. See LICENSE.