[TUHS] Shell control through external commands

Random832 random832 at fastmail.com
Mon Sep 12 08:13:19 AEST 2016


On Sun, Sep 11, 2016, at 14:50, Sven Mascheck wrote:
> I tried to follow all the traces of #! and collected the results on
> http://www.in-ulm.de/~mascheck/various/shebang/
> I'd be happy to add and fix stuff, if somebody spots anything.

DEMOS (the soviet version of Unix) seems to have an independent
implementation that supports some features no-one else does

- use $* to define where the passed-in arguments [including the script
name] go between the interpreter-arguments specified on the #!-line
- alternate magic "/*#!"

I don't remember where I downloaded it from, I think maybe someone
posted it here a few years ago.

Relevant bits from sys1.c:

# define SCRMAG  "#!"
# define SCRMAG2 "/*#!"
# define ARGPLACE "$*"

     /* формат:
         пусть есть файл   /.../.../x
         со следующим содержимым:
         -------------------------------
         |#!CMD A1 A2 A3
         | .......

        Вызываем команду:
                x B1 B2

        Запустится на самом деле такая команда:
                CMD A1 A2 A3 /.../.../x B1 B2

        Один из аргументов Ai может иметь вид $*
        Тогда аргументы запуска подставятся на это место, а не в конец:
         -------------------------------
         |#!CMD A1 $* A2 A3
         | .......

        Вызываем:
                x B1 B2

        Запустится:
                CMD A1 /.../.../x B1 B2 A2 A3
     */

There's no comment describing the SCRMAG2 feature but you can see it
used in code:

        if (indir < NSYMLNK && u.u_offset > (off_t)2 ){
            cp = (char *) &u.u_exdata;
            if( !bcmp(cp, SCRMAG, 2 ))
                off = (off_t) 2;
            else if( u.u_offset > (off_t)4 && !bcmp( cp, SCRMAG2, 4))
                off = (off_t) 4;


Sole uses of these features in the source tree:

cmd/OPQRS/spline.c,v:@/*#!/bin/cc -O $* -o spline
cmd/EFGHIJK/glob.c,v:@/*#!/bin/cc -o glob


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