Re: Question about start-process and argument list

[Jean Louis <bugs@gnu.support>]

* Eric Abrahamsen <eric@ericabrahamsen.net> [2023-02-03 09:37]:
> I recently got a bug report about the Mairix search engine for Gnus --
> long story short, the gnus-search.el code calls all command-line mail
> indexers (notmuch, mairix, namazu, etc) like this:
> 
> (apply #'start-process (format "search-%s" server)
> 			buffer program cp-list)
> 
> Where `program' is the indexer, and `cp-list' is a list of command-line
> flags. The important thing is that the last element of `cp-list' is the
> search-query string itself, but this string has not been split on
> spaces. Meaning that cp-list could look like:

I would not try to generalize the command for all search engines
unless they really have compatible command lie.

> '("--rcfile" config-file "-r" "another-arg" "from:bob subject:lunch")

Which is OK in itself, as it is safer to run program without using
external shell.

> Other search engines seem to accept this fine, but Mairix fails unless
> the search query is also split on spaces:
> 
> '("--rcfile" config-file "-r" "another-arg" "from:bob" "subject:lunch")
> 
> It occurred to me that this is probably the way it should be done, even
> if the other engines don't happen to be choking on the format. I have
> two questions:
> 
> 1. What does the program actually see, in this case? Is the first
>    example above, is it the equivalent of (on the command line) wrapping
>    the query in double quotes?

It has same effect.

> 2. Should I be using `start-process-shell-command' instead? The docs
>    mention that the main difference is that it will use shell features,
>    which aren't really relevant here, but maybe it's the right thing to
>    do, semantically.

Rather no, as that becomes unsafe. Yes, it would invoke shell and
some environment and the program line. But for programing purposes is
unsafe. 

I learned it from experience ahat `start-process' and `call-process'
are safe way and more conclusive for programming purposes.

-- 
Jean

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