From: John Carter <john.carter@...>
Date: 2007-06-28T11:57:29+09:00
Subject: Hash banging #! - Distributing precompiled sharable linux binaries

This may, in a very odd set of circumstances, be useful to somebody....

If you try interpret a #! script with another #! script it fails. (I wrote about this problem before..)
   http://tinyurl.com/287pez

One fix is to use #!/usr/bin/env in the interpreted script, but
doesn't help you is you wish, as I did, to interpose something between
lots and lots of #!/usr/bin/ruby scripts and ruby.

Here is another way, write a wee C program that does it for you....

In this case it wraps a ruby in an invocation of ld-linux.so.2 that
loads up the copies of the latest libraries so a precompiled version
will run on an old machine / distro....


// Autogenerated

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>

const char LD_LINUX   []="/opt/ruby/ruby-1.8.6-p36/dll_hell-1.0/ld-linux.so.2";
const char DLL_HELL   []="/opt/ruby/ruby-1.8.6-p36/dll_hell-1.0";
const char BARE_RUBY  []="/opt/ruby/ruby-1.8.6-p36/bin/.__bare__ruby";
/* We've been called as...
    ruby arg_1 arg_2... arg_argc-1

    must call..
     ld-linux-so.2 --library-path dll_hell /opt/..../bare_ruby
*/

int main( int argc, char * argv[])
{
    int i;
    int new_argc = argc+3;
    const char ** new_argv = (const char**)malloc( sizeof(char*)*new_argc + 1);

/*
    printf("argc=%d\n",argc);
    for( i = 0; i <= argc; ++i) {
       printf( "argv[%3d]=%s\n",i, argv[i]);
    }
*/
    new_argv[0] = "ruby";
    new_argv[1] = "--library-path";
    new_argv[2] = DLL_HELL;
    new_argv[3] = BARE_RUBY;

    for( i = 1; i <= argc; ++i) {
       new_argv[i+3] = argv[i];
    }
/*
    printf("\nnew_argc=%d\n",new_argc);
    for( i = 0; i <= new_argc; ++i) {
       printf( "new_argv[%3d]=%s\n",i, new_argv[i]);
    }

*/
    execv( LD_LINUX, (char * const *)new_argv);

    perror( "Should haved execv'ed!");
    return 1;
}




John Carter                             Phone : (64)(3) 358 6639
Tait Electronics                        Fax   : (64)(3) 359 4632
PO Box 1645 Christchurch                Email : john.carter@tait.co.nz
New Zealand