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Annotation of 42BSD/games/compat/modshell/compat.c, revision 1.1

1.1     ! root        1: #include "defs.h"
        !             2: #define BS 8
        !             3: #define        MAXARGS 300
        !             4: short buf[BS];
        !             5: /*
        !             6:  *     Check for possible program to run under alternate runtime system
        !             7:  *     If it checks out, start the rts and pass file and args
        !             8:  *     Art Wetzel 3/13/80
        !             9:  */
        !            10: compat(file, argv, envp) char *file, *argv[], *envp[]; {
        !            11:        register int fd;
        !            12:        register char *rts;
        !            13:        register char **nargv;
        !            14:        char    *nargs[MAXARGS];
        !            15:        /* alternate rts images must be readable */
        !            16:        /* if not just go back and let rest of shell worry about it */
        !            17:        if((fd = open(file,0))<0)
        !            18:                return(0);
        !            19:        /* read first BS pdp-11 words */
        !            20:        if(read(fd,buf,sizeof buf) != sizeof buf) {
        !            21:                close(fd);
        !            22:                /* if can't, go back as it may be a short shell file */
        !            23:                return(0);
        !            24:        }
        !            25:        close(fd);
        !            26:        /* check type of image and set up run time system name */
        !            27:        if(buf[0]==0407 || buf[0]==0410 || buf[0]==0411 || buf[0]==0405) {
        !            28:                /* looks like UNIX a.out file */
        !            29:                /* RTS or default rts */
        !            30:                if((rts = rtsnod.namval) == 0)
        !            31:                        rts = defrts;
        !            32:                /* if header unused is set to 1 force version 6 */
        !            33:                /* this is not a real difference between v6 and v7 a.outs */
        !            34:                /* rather, version 6 a.outs were patched to be identifiable */
        !            35:                if(buf[6] == 1)
        !            36:                        rts = "/usr/bin/v6run";
        !            37:        } else if(buf[6] == 0) {
        !            38:                /* it looks like almost all RT-11 save images have 0 here */
        !            39:                rts = "/usr/bin/rtrun";
        !            40:        } else {
        !            41:                /* was not a recognizable file type */
        !            42:                return(0);
        !            43:        }
        !            44:        /* must make a new argv list with runtime system prefix */
        !            45:        nargv = &nargs[0];
        !            46:        *nargv++ = rts;
        !            47:        /* have to pass full file name to rts */
        !            48:        *nargv++ = file;
        !            49:        argv++;
        !            50:        while(*argv && nargv < &nargs[MAXARGS-1])
        !            51:                *nargv++ = *argv++;
        !            52:        /* force in final null */
        !            53:        *nargv++ = (char *)0;
        !            54:        /* try to start rts */
        !            55:        execve(nargs[0], nargs, envp);
        !            56:        /* if that failed, report no runtime system */
        !            57:        failed(nargs[0], norts);
        !            58: }

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