Shexp is composed of two parts: a library providing a process monad for shell scripting in OCaml as well as a simple s-expression based shell interpreter. Shexp works on both Unix and Windows.

Shexp defines a few libraries that can be used independently.

Shexp_spawn is a small library exposing only one function: Shexp_spawn.spawn. Its purpose is to start command in the background. Shexp_spawn aims to provide a few missing features of Unix.create_process such as providing a working directory as well as improving errors reporting and performances.

Errors such as directory or program not found are properly reported as Unix.Unix_error exceptions, on both Unix and Windows.

On Unix, Shexp_spawn uses vfork by default as it is often a lot faster than fork. There is a benchmark comparing Shexp_spawn.spawn to Unix.create_process in spawn-lib/bench. If you don’t trust vfork, you can set the environment variable SHEXP_USE_FORK to make Shexp_spawn use fork instead.