Paul-
Minor historical note. The `#!' processing was never done by the
shell, this was always done in the kernel. Think about about it,
the `#' character denotes a comment line, the shell ignores that
line. `#!' was used to create a way for the kernel to execute
a shell script directly. Since the kernel recognized the type of
executable based on a 16-bit magic number `#!' became a new magic
number that meant "break the remainder of the line into `program'
and `args' and then execute `program' with `args'".
A nice side effect of this is that it became a way to create shell
scripts that worked no matter what shell a user was running. For
efficiency, most shells just read and execute a shell script so
releasing a Bourne shell script to a group of CSH users created
problems. At the expense of a `fork' and `exec' the `#!' magic
number solved this problem.
On Tue, Mar 06, 2001 at 12:33:49PM +0000, Paul Flinders wrote:
> Andreas Schwab wrote:
>
> > Paul Flinders <[EMAIL PROTECTED]> writes:
> >
> > |> Andreas Schwab wrote:
> > |>
> > |> > This [isspace('\r') == 1] has no significance here. The right thing to
> > |>
> > |> > look at is $IFS, which does not contain \r by default. The shell only splits
> > |>
> > |> > words by "IFS whitespace", and the kernel should be consistent with it:
> > |> >
> > |> > $ echo -e 'ls foo\r' | sh
> > |> > ls: foo: No such file or directory
> > |>
> > |> The problem with that argument is that #!<interpreter> can be applied
> > |> to more than just shells which understand $IFS, so which environment
> > |> variable does the kernel pick?
> >
> > The kernel should use the same default value of IFS as the Bourne shell,
> > ie. the same value you'll get with /bin/sh -c 'echo "$IFS"'. This is
> > independent of any settings in the environment.
> >
> > |> It's a difficult one - logically white space should terminate the interpreter
> >
> > No, IFS-whitespace delimits arguments in the Bourne shell.
>
> Way back whenever processing #! was moved from the
> shell to the kernel** this argument would have made sense -
> today I'm not so sure.
>
> But I'm quite happy for the kernel to use just space and
> tab if it wishes, or anything else for that matter but it _is_
> confusing that the error code doesn't distinguish problems
> with the script from problems with the interpreter.
>
> **Did linux ever rely on the shell for this?
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to [EMAIL PROTECTED]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
--
Don Dugger
"Censeo Toto nos in Kansa esse decisse." - D. Gale
[EMAIL PROTECTED]
Ph: 303/938-9838
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
