Various interpreter modes such as Shell script mode or AWK mode will
automatically insert or update the buffer’s magic number, a special
comment on the first line that makes the
exec systemcall know
how to execute the script. To this end the script is automatically
made executable upon saving, with
executable-chmod as argument
to the system
chmod command. The magic number is prefixed by
the value of
Any file whose name matches
executable-magicless-file-regexp is not
furnished with a magic number, nor is it made executable. This is mainly
intended for resource files, which are only meant to be read in.
executable-insert says what to do when
executable-set-magic is called non-interactively, e.g., when file has no
or the wrong magic number:
Insert or update magic number.
Insert or update magic number, but mark as unmodified.
executable-query controls whether to ask about
inserting or updating the magic number. When this is
is only done with M-x executable-set-magic. When this is
function you are queried whenever
called as a function, such as when Emacs puts a buffer in Shell script
mode. Otherwise you are always queried.