Genspio is a typed EDSL to generate shell scripts and commands from OCaml.
The idea is to build values of type 'a EDSL.t
with the
combinators in the Genspio.EDSL
module, and compile them to POSIX
shell scripts (or one-liners) with functions from Genspio.Compile
.
See the file
src/examples/small.ml
which generates a useful list of usage examples, or the
section “Getting Started” below.
The tests run the output of the compiler against a few shells that it tries to
find on the host (e.g. dash
, bash
, busybox
, mksh
, zsh
… cf. the
example test results summary below).
If you have any questions, do not hesitate to submit an issue.
Genspio's documentation root is at https://smondet.gitlab.io/genspio-doc/.
You can install the library though opam
:
opam install genspio
Or get the development version with opam pin
:
opam pin add genspio https://github.com/hammerlab/genspio.git
You can also build locally:
You need OCaml ≥ 4.03.0 together with base
, fmt
, and
dune
:
dune build @install
Here is a quick example:
utop> open Genspio.EDSL;;
utop>
let c =
let username_one_way : str t =
(* We lift the string "USER" to EDSL-land and use function `getenv`: *)
getenv (str "USER") in
let username_the_other_way : str t =
(* The shell-pipe operator is `||>` *)
(exec ["whoami"] ||> exec ["tr"; "-d"; "\\n"])
(* `get_stdout` takes `stdout` from a `unit t` as a `byte_array t` *)
|> get_stdout
in
let my_printf : string -> str t list -> unit t = fun fmt args ->
(* The function `call` is like `exec` but operates on `str t` values
instead of just OCaml strings: *)
call (str "printf" :: str fmt :: args) in
(* The operator `=$=` is `str t` equality, it returns a `bool t` that
we can use with `if_seq`: *)
if_seq Str.(username_one_way =$= username_the_other_way)
~t:[
my_printf "Username matches: `%s`\\n" [username_one_way];
]
~e:[
my_printf "Usernames do not match: `%s` Vs `%s`\\n"
[username_one_way; username_the_other_way];
]
;;
val c : unit t
utop> Sys.command (Genspio.Compile.to_one_liner c);;
Username matches: `smondet`
- : int = 0
Genspio.EDSL
provides the Embedded Domain Specific Language API to build
shell script expressions (there is also a lower-level, not recommended,
Genspio.EDSL_v0
API).Genspio.Compile
has the 3 “compilers” provided by the library:
'a EDSL.t
values as expressions of a
lisp-like pseudo-language.To_posix
” compiler generates POSIX-compliant shell
scripts (with the option of avoiding new-lines).bash
version is buggy and has been
witnessed to choke on generated POSIX-valid scripts.To_slow_flow
” compiler generates POSIX shell scripts which
are much simpler, hence more portable across shell implementations, but
use (a lot of) temporary files and are generally slower.Genspio.Transform
implements code transformations:
Visitor
provides an extensible AST visitor.Constant_propagation
does some basic constant propagation
(using the visitor).src/examples/small.ml
which are used to generate the usage examples documentation webpage.src/examples/service_composer.ml
is the code generator for the “COSC” project (Github:
smondet/cosc
), a family of scripts which
manage long-running processes in a GNU-Screen session.src/examples/downloader.ml
contains another big example: a script that downloads and unpacks archives
from URLs.src/examples/vm_tester.ml
is a “Makefile + scripts” generator to setup Qemu virtual machines, they can
be for instance used to run the tests on more exotic platforms.hammerlab/secotrec
is a real-world,
larger-scale use of Genspio (uses Genspio version 0.0.0).From here, one can explore:
Genspio.EDSL_v0
is an older version of the API, which can still
be useful as it is lower-level: it gives full access to the two “string-like”
types, byte-arrays and C-strings while of course becoming more cumbersome to
use.
To run the tests you also need make
and there is an additional dependency on
the uri
library, see:
genspio_test=_build/default/src/test/main.exe
dune build $genspio_test
$genspio_test --help
Try this:
$genspio_test --important-shells bash,dash /tmp/gtests/
cd /tmp/gtests/
make run-all # Attempts to run all the tests on all the shells
make check # Checks that all the tests for the important ones succeeded
You can generate a markdown report with make report
and check report.md
.
Some failures are expected with not-really-POSIX or buggy shells like
KSH93, or on some corner cases
cf. #35
.
You can check failures in the <shell-test>/failures.md
files, see for instance
ksh-StdML/failures.md
for the failures of the “KSH with standard Genspio
compilation to multi-line scripts” (similarly there are
<shell-test>/successes.md
files).
To build the documentation one needs pandoc
and caml2html
:
sh tools/build-doc.sh
The build of the whole website, including the web-based demo, happens in a different repository: https://gitlab.com/smondet/genspio-doc.
It's Apache 2.0.