Program working with shell-command but not call-process

Program working with shell-command but not call-process

[John Mastro]

Does anyone know what situation would result in this working:

    (shell-command-to-string "git --version")
    ;=> it returns "git version 2.0.1"

But not this:

    (with-output-to-string
      (call-process "git" nil standard-output nil "--version"))
      ;=> it returns ""
      ;=> `call-process' alone returns 53

This git is built and installed from source on Cygwin. It works fine
from the shell but not via `call-process', which means it doesn't work
with `magit'.

It's in my path (both $PATH and `exec-path'), and `executable-find'
finds it without problem at c:/usr/local/bin/git.exe.

The git that's availablefor install via Cygwin (quite old, v1.7.9),
succeeds with both the calls above. It's still installed at
c:/bin/git.exe.

Thanks,

John

Re: Program working with shell-command but not call-process

[Michael Heerdegen]

John Mastro <john.b.mastro@gmail.com> writes:

> Does anyone know what situation would result in this working:
>
>     (shell-command-to-string "git --version")
>     ;=> it returns "git version 2.0.1"
>
> But not this:
>
>     (with-output-to-string
>       (call-process "git" nil standard-output nil "--version"))
>       ;=> it returns ""
>       ;=> `call-process' alone returns 53

Don't know anything about this, sorry.  But considering the doc of
`call-process` - when you don't get a lisp error, Emacs found and
actually called git, and git exited with return value 53.

Dunno what makes the difference when you use a shell.

Michael.

Re: Program working with shell-command but not call-process

[Joost Kremers]

John Mastro wrote:
> Does anyone know what situation would result in this working:
>
>     (shell-command-to-string "git --version")
>     ;=> it returns "git version 2.0.1"
>
> But not this:
>
>     (with-output-to-string
>       (call-process "git" nil standard-output nil "--version"))
>       ;=> it returns ""
>       ;=> `call-process' alone returns 53

`with-output-to-string' takes whatever is sent to `standard-output',
converts it to a string and returns it. `call-process' sends its output
to a buffer, or optionally to a file, but not to stdout. So you won't
get any output from this construct unless `standard-output' is set to a
buffer.

However, that is probably not the source of the problem you hint at (the
fact that magit doesn't work). That is most likely due to the fact that
`call-process' alone returns 53. If git were successful, it should
return 0.


-- 
Joost Kremers                                   joostkremers@fastmail.fm
Selbst in die Unterwelt dringt durch Spalten Licht
EN:SiS(9)

Re: Program working with shell-command but not call-process

[Michael Heerdegen]

Joost Kremers <joost.m.kremers@gmail.com> writes:

> >     (with-output-to-string
> >       (call-process "git" nil standard-output nil "--version"))
> >       ;=> it returns ""
> >       ;=> `call-process' alone returns 53
>
> `with-output-to-string' takes whatever is sent to `standard-output',
> converts it to a string and returns it. `call-process' sends its output
> to a buffer, or optionally to a file, but not to stdout. So you won't
> get any output from this construct unless `standard-output' is set to a
> buffer.

I don't think this is true.  `with-output-to-string` binds
`standard-output` to a temporary buffer and returns its content, so the
above should work (and actually does work here).

Michael.