[Caml-list] opam local switch

[Caml-list] opam local switch

[Yotam Barnoy]

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I have a question about opam. I would like to play with certain compiler
versions, but I don't want the switch to happen globally, because I still
need to compile regular code. Is it possible to switch to another compiler
locally (within a particular shell session) via environment variables,
while using my regular compiler in another shell session?

If this is the way things work already, I apologize in advance -- it
appeared to me that running opam switch modifies some global state that
directly affects other pre-existing shell sessions.

-Yotam

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Re: [Caml-list] opam local switch

[Anil Madhavapeddy]

On 18 Sep 2014, at 22:20, Yotam Barnoy <yotambarnoy@gmail.com> wrote:

> I have a question about opam. I would like to play with certain compiler versions, but I don't want the switch to happen globally, because I still need to compile regular code. Is it possible to switch to another compiler locally (within a particular shell session) via environment variables, while using my regular compiler in another shell session?
> 
> If this is the way things work already, I apologize in advance -- it appeared to me that running opam switch modifies some global state that directly affects other pre-existing shell sessions.

It's worth reading the man page for OPAM ("man opam" or "opam --help"), which lists all the environment variables and command-line options available.

There is OPAMSWITCH (or the command line --switch option) which will fix a particular switch to run the opam command set in.

best,
Anil

Re: [Caml-list] opam local switch

[Yotam Barnoy]

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OPAMSWITCH appears undocumented, though it's referred to in the man page
under opam --switch ("This is equivalent to setting $OPAMSWITCH")

My question is, if I set OPAMSWITCH, will I then be able to run regular
(non-opam) ocaml build commands in the local shell in the given compiler,
while running commands in a different shell with a different compiler? If
not, is such a feature planned?

-Yotam

On Thu, Sep 18, 2014 at 5:24 PM, Anil Madhavapeddy <anil@recoil.org> wrote:

> On 18 Sep 2014, at 22:20, Yotam Barnoy <yotambarnoy@gmail.com> wrote:
>
> > I have a question about opam. I would like to play with certain compiler
> versions, but I don't want the switch to happen globally, because I still
> need to compile regular code. Is it possible to switch to another compiler
> locally (within a particular shell session) via environment variables,
> while using my regular compiler in another shell session?
> >
> > If this is the way things work already, I apologize in advance -- it
> appeared to me that running opam switch modifies some global state that
> directly affects other pre-existing shell sessions.
>
> It's worth reading the man page for OPAM ("man opam" or "opam --help"),
> which lists all the environment variables and command-line options
> available.
>
> There is OPAMSWITCH (or the command line --switch option) which will fix a
> particular switch to run the opam command set in.
>
> best,
> Anil
>
>

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Re: [Caml-list] opam local switch

[Grégoire Henry]

Hi,

> My question is, if I set OPAMSWITCH, will I then be able to run regular
> (non-opam) ocaml build commands in the local shell in the given compiler,
> while running commands in a different shell with a different compiler?

No, it is not. But, what you are looking for is probably:

  eval $(opam config env --switch 3.12.1)

This will setup the proper environment for ocaml-3.12.1 in the current
terminal (including the OPAMSWITCH variable) without changing the
"global default switch".

The previous command is equivalent to:

  export OPAMSWITCH=3.12.1
  eval $(opam config env)

-- Grégoire

Re: [Caml-list] opam local switch

[Yotam Barnoy]

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Awesome, thanks.

On Thu, Sep 18, 2014 at 6:28 PM, Grégoire Henry <gregoire.henry@ocamlpro.com
> wrote:

> Hi,
>
> > My question is, if I set OPAMSWITCH, will I then be able to run regular
> > (non-opam) ocaml build commands in the local shell in the given compiler,
> > while running commands in a different shell with a different compiler?
>
> No, it is not. But, what you are looking for is probably:
>
>   eval $(opam config env --switch 3.12.1)
>
> This will setup the proper environment for ocaml-3.12.1 in the current
> terminal (including the OPAMSWITCH variable) without changing the
> "global default switch".
>
> The previous command is equivalent to:
>
>   export OPAMSWITCH=3.12.1
>   eval $(opam config env)
>
> -- Grégoire
>

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Re: [Caml-list] opam local switch

[Louis Gesbert]

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Le jeudi 18 septembre 2014, 17:20:37 Yotam Barnoy a écrit :
> I have a question about opam. I would like to play with certain compiler
> versions, but I don't want the switch to happen globally, because I still
> need to compile regular code. Is it possible to switch to another compiler
> locally (within a particular shell session) via environment variables,
> while using my regular compiler in another shell session?
> 
> If this is the way things work already, I apologize in advance -- it
> appeared to me that running opam switch modifies some global state that
> directly affects other pre-existing shell sessions.
> 
> -Yotam
> 
> 

This is already in our new FAQ [1] :)
We're just waiting for 1.2 to be out before we post the new doc pages, because some of it doesn't apply to the current 1.1 stable release. OPAM 1.2 is still in RC stage.


[1] 
http://opam.ocaml.org/doc/1.2/FAQ.html#CanIworkondifferentswitchesatthesametimeindifferentshells

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Re: [Caml-list] opam local switch

[Gabriel Scherer]

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Note that you can also use

  opam config exec --switch=<SWITCH> -- <COMMAND>

to execute a command with a local switch choice. This is very helpful in
contexts where you don't exactly remember how to setup the environment (eg.
when prompted for an in-Emacs compilation command), or you want to play
with several versions alternatively in a single terminal (testing a
regression in new OCaml versions).

On Fri, Sep 19, 2014 at 9:21 AM, Louis Gesbert <louis.gesbert@ocamlpro.com>
wrote:

>  Le jeudi 18 septembre 2014, 17:20:37 Yotam Barnoy a écrit :
>
> > I have a question about opam. I would like to play with certain compiler
>
> > versions, but I don't want the switch to happen globally, because I still
>
> > need to compile regular code. Is it possible to switch to another
> compiler
>
> > locally (within a particular shell session) via environment variables,
>
> > while using my regular compiler in another shell session?
>
> >
>
> > If this is the way things work already, I apologize in advance -- it
>
> > appeared to me that running opam switch modifies some global state that
>
> > directly affects other pre-existing shell sessions.
>
> >
>
> > -Yotam
>
> >
>
> >
>
>
>
> This is already in our new FAQ [1] :)
>
> We're just waiting for 1.2 to be out before we post the new doc pages,
> because some of it doesn't apply to the current 1.1 stable release. OPAM
> 1.2 is still in RC stage.
>
>
>
>
>
> [1]
>
>
> http://opam.ocaml.org/doc/1.2/FAQ.html#CanIworkondifferentswitchesatthesametimeindifferentshells
>

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