Changing rc to understand about shell scripts with no magic number

Changing rc to understand about shell scripts with no magic number

[Solid Hogan]

On most systems there are many shell scripts without the #! magic number.
These are supposed to be interpreted by /bin/sh; their authors assumed
that this would automatically happen.

Under rc, however, something different happens.  If you were to attempt to
run, for instance, clear, on our system you would get:

clear: Exec format error

The following patch to exec.c detects the ENOEXEC error, and runs /bin/sh
on the offending file:

*** exec.c.old	Sun Jun 30 22:17:04 1991
--- exec.c	Sun Jun 30 22:16:20 1991
***************
*** 6,11 ****
--- 6,12 ----
  
  #include <setjmp.h>
  #include <signal.h>
+ #include <sys/errno.h>
  #include "rc.h"
  #include "utils.h"
  #include "exec.h"
***************
*** 98,103 ****
--- 99,119 ----
  			rc_exit(getstatus());
  		}
  		execve(path, (char **)av, (char **)ev); /* bogus, huh? */
+ 		if (errno == ENOEXEC)
+ 		{
+ 			char	**av2;
+ 			int	num, i;
+ 
+ 			num = listnel(s);
+ 			av2 = (char **) nalloc((num + 2) * sizeof (char *));
+ 			for (i = 1; i <= num; i++)
+ 				av2[i+1] = av[i];
+ 			av2[0] = av[0];
+ 			av2[1] = path;
+ 			execve("/bin/sh", (char **)av2, (char **)ev);
+ 			uerror(*av);
+ 			rc_exit(1);
+ 		}
  		uerror(*av);
  		rc_exit(1);
  		/* NOTREACHED */