[BusyBox] sh valid char for variable

[Larry Doolittle]

Vladimir -

> I see good work with sh.c

Thanks!

> strpbrk(dst+1, " \t~`!$^&*()=|\\[];\"'<>?./"); is VERY strange.

:-)

> See patch to sh.c base from real sh parser.

First question: what "real sh parser"?
I'd love to get a look at the original Bell Labs code.

+       local_pending_command = xstrdup(cmd);

Of course.

-       const char *out_of_space = "out of space during expansion";
+       static const char out_of_space[] = "out of space during expansion";

That's a clear improvement, too.

+             if(isascii(*src) && (isalpha(*src) || *src == '_')) {
+                      src++;
+                      while(isascii(*src) && (isalpha(*src)
+                                      || *src == '_'
+                                      || isdigit(*src)))
+                                            src++;

I don't understand the purpose to isascii, or why you explicitly
call out isalpha || isdigit, instead of using isalnum. Apart from
those minor details, your suggested behavior is more correct, so
I support changing it to something like this.  You see that code
size is probably larger.  The desire for small size probably
motivated the original usage of strpbrk().

-                       delim_hold=*src;
+                       delim_hold = *src;
                        *src='\0';  /* temporary */
-                       var = getenv(dst + num_skip_chars);
-                       *src=delim_hold;
-                       if (num_skip_chars==2) {
-                               src++;
-                       }
+                       var = getenv(dst + num_skip_chars + 1);
+                       *src = delim_hold + num_skip_chars;

That last line is totally bogus.  You have to restore the
original string with "*src = delim_hold;" no matter what
num_skip_chars is.

        - Larry