From: ara.t.howard@...
Date: 2006-04-25T12:07:55+09:00
Subject: Re: Format of RUBYOPT

On Tue, 25 Apr 2006, Ryan Leavengood wrote:

> On 4/24/06, ara.t.howard@noaa.gov <ara.t.howard@noaa.gov> wrote:
>>
>> if you look in ruby.c you'll see that it's literally parsed as part of the
>> commandline - except only the switchs 'IdvwrK' and 'T' are accepted.  it looks
>> like it is indeed space separated.
>>
>>    harp:~ > cat rubylib/a.rb
>>    A=42
>>
>>    harp:~ > RUBYOPT="-ryaml -Irubylib/ -ra" ruby -e "p [YAML, A]"
>>    [YAML, 42]
>>
>> seems to work.
>
> Hmmm, OK. Then why does setting RUBYOPT to just rubygems work (it has
> no dash?) That doesn't work on the command-line (at least on Windows):
>
> C:\_Ryan\ruby_installer\svn\NSIS>ruby rubygems -e 'puts "hello"'
> ruby: No such file or directory -- rubygems (LoadError)
>
> C:\_Ryan\ruby_installer\svn\NSIS>ruby -rubygems -e 'puts "hello"'
> hello
>
> Maybe to be safe I should always just add -rubygems (i.e with a dash prefix.)

ruby.c, in proc_options:


     731     if (rb_safe_level() == 0 && (s = getenv("RUBYOPT"))) {
     732         while (ISSPACE(*s)) s++;
     733         if (*s == 'T' || (*s == '-' && *(s+1) == 'T')) {
     734             int numlen;
     735             int v = 1;
     736
     737             if (*s != 'T') ++s;
     738             if (*++s) {
     739                 v = scan_oct(s, 2, &numlen);
     740                 if (numlen == 0) v = 1;
     741             }
     742             rb_set_safe_level(v);
     743         }


in the else block we eat the dash and any space, iff present.  then we look
for the opt char


     744         else {
     745             while (s && *s) {
     746                 if (*s == '-') {
     747                     s++;
     748                     if (ISSPACE(*s)) {
     749                         do {s++;} while (ISSPACE(*s));
     750                         continue;
     751                     }
     752                 }
     753                 if (!*s) break;
     754                 if (!strchr("IdvwrK", *s))
     755                     rb_raise(rb_eRuntimeError, "illegal switch in RUBYOPT: -%c", *s);


now, given RUBYOPT=-rubygems, and *s==r, we call moreswitches


     756                 s = moreswitches(s);
     757             }
     758         }
     759     }


so in this function


     433 static char*
     434 moreswitches(s)
     435     char *s;
     436 {
     437     int argc; char *argv[3];
     438     char *p = s;
     439
     440     argc = 2; argv[0] = argv[2] = 0;
     441     while (*s && !ISSPACE(*s))
     442         s++;
     443     argv[1] = ALLOCA_N(char, s-p+2);
     444     argv[1][0] = '-';
     445     strncpy(argv[1]+1, p, s-p);
     446     argv[1][s-p+1] = '\0';
     447     proc_options(argc, argv);
     448     while (*s && ISSPACE(*s))
     449         s++;
     450     return s;
     451 }


we eat whitespace, setup argv=[0, "-rubygems", 0] and argc == 2.  then recurse
into proc_options (the first method shown).


so, as far as i can tell (and i've had three beers), proc_options finds the
'r', jumps into moreswitches which restores the '-', and the were back into
proc_options with '-rubygems', which works because of the 'ubygems' hack.  the
parsing of RUBYOPT looks as if it ignores '-' or lack thereof be design, but i
certainly can't be knowing.

good luck!  ;-)

-a
-- 
be kind whenever possible... it is always possible.
- h.h. the 14th dali lama