compile mode and $EMACS

compile mode and $EMACS

[Sebastian Wiesner]

Hello,

I just discovered that compile mode adds "EMACS=t" to the process
environment (see "compilation-start").

What is this variable for?  How is it supposed to be interpreted by
the invoked program?  Which programs do actually use it?

Greetings

Re: compile mode and $EMACS

[Xue Fuqiao]

On Sun, Aug 11, 2013 at 12:47 AM, Sebastian Wiesner <lunaryorn@gmail.com> wrote:
> Hello,
>
> I just discovered that compile mode adds "EMACS=t" to the process
> environment (see "compilation-start").
>
> What is this variable for?  How is it supposed to be interpreted by
> the invoked program?  Which programs do actually use it?

In (info "(emacs) Interactive Shell"):

     Emacs sets the environment variable `INSIDE_EMACS' in the subshell
  to `VERSION,comint', where VERSION is the Emacs version (e.g., `24.1').
  Programs can check this variable to determine whether they are running
  inside an Emacs subshell.  (It also sets the `EMACS' environment
  variable to `t', if that environment variable is not already defined.
  However, this environment variable is deprecated; programs that use it
  should switch to using `INSIDE_EMACS' instead.)

-- 
Best regards, Xue Fuqiao.
http://www.gnu.org/software/emacs/

Re: compile mode and $EMACS

[Sebastian Wiesner]

2013/8/11 Xue Fuqiao <xfq.free@gmail.com>:
> On Sun, Aug 11, 2013 at 12:47 AM, Sebastian Wiesner <lunaryorn@gmail.com> wrote:
>> Hello,
>>
>> I just discovered that compile mode adds "EMACS=t" to the process
>> environment (see "compilation-start").
>>
>> What is this variable for?  How is it supposed to be interpreted by
>> the invoked program?  Which programs do actually use it?
>
> In (info "(emacs) Interactive Shell"):

Thank you.

Re: compile mode and $EMACS

[Pascal J. Bourguignon]

Sebastian Wiesner <lunaryorn@gmail.com> writes:

> Hello,
>
> I just discovered that compile mode adds "EMACS=t" to the process
> environment (see "compilation-start").
>
> […] How is it supposed to be interpreted by the invoked program?  […]

Some compilers may have different error message output formats depending
on whether they're run INSIDE_EMACS or not.

For example, ant has the -e option to output emacs friendly formatted
error messages.

(Of course, emacs can also adapt itself to the various compiler error
message output formats, cf. C-h v compilation-error-regexp-alist)


-- 
__Pascal Bourguignon__
http://www.informatimago.com/

Re: compile mode and $EMACS

[Sebastian Wiesner]

2013/8/11 Pascal J. Bourguignon <pjb@informatimago.com>:
> Sebastian Wiesner <lunaryorn@gmail.com> writes:
>
>> Hello,
>>
>> I just discovered that compile mode adds "EMACS=t" to the process
>> environment (see "compilation-start").
>>
>> […] How is it supposed to be interpreted by the invoked program?  […]
>
> Some compilers may have different error message output formats depending
> on whether they're run INSIDE_EMACS or not.

Which ones?  Can you name *concrete* examples?

> For example, ant has the -e option to output emacs friendly formatted
> error messages.

Yes, uhm, that's an explicit option to enable Emacs-friendly
formatting.  Many tools have those.  But I see no $EMACS variable
involved here…

Re: compile mode and $EMACS

[Andreas Schwab]

Sebastian Wiesner <lunaryorn@gmail.com> writes:

> Which ones?  Can you name *concrete* examples?

bash:
  /*
   * M-x term -> TERM=eterm EMACS=22.1 (term:0.96)	(eterm)
   * M-x shell -> TERM=dumb EMACS=t			(no line editing)
   * M-x terminal -> TERM=emacs-em7955 EMACS=		(line editing)
   */
  if (interactive_shell)
    {
      char *term, *emacs;

      term = get_string_value ("TERM");
      emacs = get_string_value ("EMACS");

      /* Not sure any emacs terminal emulator sets TERM=emacs any more */
      no_line_editing |= term && (STREQ (term, "emacs"));
      no_line_editing |= emacs && emacs[0] == 't' && emacs[1] == '\0' && STREQ (term, "dumb");

      /* running_under_emacs == 2 for `eterm' */
      running_under_emacs = (emacs != 0) || (term && STREQN (term, "emacs", 5));
      running_under_emacs += term && STREQN (term, "eterm", 5) && emacs && strstr (emacs, "term");

      if (running_under_emacs)
	gnu_error_format = 1;
    }

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."