Path: utzoo!attcan!uunet!munnari.oz.au!cluster!atom!rjc
From: rjc@atom.OZ (Robert Cawley)
Newsgroups: comp.sys.ibm.pc
Subject: Re: How can I set a PATH longer than 128 bytes?
Message-ID: <1486@atom.OZ>
Date: 9 Mar 90 13:35:16 GMT
References: <5762@ncrcae.Columbia.NCR.COM> <31300010@inmet> <25f1ea76.25da@polyslo.CalPoly.EDU>
Reply-To: rjc@atom.oz.au (Robert Cawley)
Organization: Australian Nuclear Science & Technology Organisation
Lines: 227

In article <25f1ea76.25da@polyslo.CalPoly.EDU> jdudeck@polyslo.CalPoly.EDU (John R. Dudeck) writes:
>
>In article <31300010@inmet> gjs@inmet.inmet.com writes:
>>One method is to use SUBST to assign some of the directories in your
>>path to "virtual drives," then include the drives in your path.  For
>>example:
>>    subst E: C:\utility\word
>>    subst F: C:\utility\database
>>    subst G: C:\utility\sprdsht
>>    subst H: C:\utility\comm
>>
>>    path C:\bin;E:;F:;G:;H:

I missed the start of all this, but here is a program I wrote some years ago
to enable me to have a path of any size (up to the size reserved in the
environment by 
    SHELL = command.com /p /e=xxx
in config.sys, where xxx is the environment size.
The program checks for either COMSPEC=, or PATH= as the first entry in the
master environment table. This could probably be deleted, but as I only use
this in my AUTOEXEC.BAT I have not bothered to do so.
Usage is:
in autoexec.bat
    PATH=c:\;c:\bin
    PATHEX c:\usr\bin;c:\ms\c5
    PATHEX d:\zortech\bin
each PATHEX line adds the listed directories to the path.

I have used this little program for over 5 years without problems. It has been
tested with MSDOS 3.3 and 3.2, PCDOS 4.0, 3.3, 3.2, 3.1, 2.1 and 2.0 and seems
to have no problems with these.

This is compiled with Microsoft C.


#include <dos.h>
#include <malloc.h>

#define	PARA	0x10000l

char tststr[] = "COMSPEC=";
char tststr2[] = "PATH=";    
int dos33 = 0;
   
int mycmp(a, b, len)
    char huge *a;
    char *b;
    int len;
{
    int i;
    for (i = 0; i < len; i++)
        if ( *a++ != *b++ )
            return(1);
    return(0);
}

char huge *findmast(el)
    int *el;
{
    unsigned char huge *p = (unsigned char huge *) 0l;
    unsigned char huge *q;
    unsigned int    owner = 0;
    unsigned int    priown = 0;
    int len;
    int i;
    int first = 0;
    
    while (1)
    {
        while (*p != 'M')
            (long int) p += PARA;
        (long int) q = (long int) p + PARA;
        if ( (owner = *((unsigned int huge *)(p+1))) != FP_SEG(q) )
        {
            if (
                (priown &&
                 (owner == priown) &&
                 ( ( ( (len = ( *((int huge *)(p+3)) ) * 16) > strlen(tststr) ) &&
                     !mycmp(q, tststr, strlen(tststr)) ) ||
                     ( (len > strlen(tststr2)) && !mycmp(q, tststr2, strlen(tststr2))))
                )
               )
            {
                *el = len;
                return(q);
            }
            else
                p = q;
        }
        else
        {
            if ( (*((unsigned int huge *)(p + 0x2c + 0x10)) == 0)
               )
            {
                priown = FP_SEG(q);
                p = q;
            }
            else if (dos33)
            {
       	        char huge *p33;
        	FP_SEG(p33) = *((unsigned int huge *)(p + 0x2c +0x10));
            	FP_OFF(p33) = 0;
            	q = p33;
            	(long int) p33 -= PARA;
            	len = ( *((int huge *)(p33+3)) ) * 16;
            	if ( !(!mycmp(q, tststr, strlen(tststr)) ||
            	       !mycmp(q, tststr2, strlen(tststr2)) )
            	   )
                    return( (char huge *) 0l);
                *el = len;
                return(q);
            }
            else
                return( (char huge *) 0l );
       }
    }
}



addpath(ep, esv, len, path)
    char huge *ep;
    char *esv;
    int  len;
    char *path;
{
    int l;
    char huge *eps;
    char huge *oldep;
    char *oldesv;
    
    oldep = ep;
    oldesv = esv;
    l = 0;
    
    while (*ep)
    {
        eps = ep;
        while (*ep)
        {
            if (l+3 > len)
                return(1);
            *esv++ = *ep++;
            l++;
        }
        if (!mycmp(eps, "PATH=", 5))
        {
            if ( *path && ((esv[-1] == ';') ? 0 : ((esv[-1] == '=') ? 0 : 1)) )
            {
                *esv++ = ';';
                l++;
            }
            while (*path)
            {
                if (l+3 > len)
                    return(1);
                *esv++ = toupper(*path++);
                l++;
            }
        }
        *esv++ = '\0';
        ep++;
    }
    *esv++ = '\0';
    
    ep = oldep;
    esv = oldesv;
    
    while (*esv)
    {
        while (*esv)
            *ep++ = *esv++;
        *ep++ = '\0';
        esv++;
    }
    *ep++ = '\0';
    
    return(0);
}


main(argc, argv)
    int argc;
    char *argv[];
{
    char huge *ep;
    int len;
    char *esv;
    union REGS dosregs;
    
    if (argc != 2)
    {
        printf("Usage: pathex pathstring\n");
        exit(0);
    }
    dosregs.h.ah = 0x30;        /* to get dos version */
    intdos(&dosregs, &dosregs);
    switch (dosregs.h.al)
    {
        case 2:
            break;
        case 3:
            if (dosregs.h.ah == 30)
                dos33 = 1;
			break;
		case 4:                 /* I don't know if this will work */
			dos33 = 1;
			break;
        default:
            printf("Dos version %d.%d not supported\n", dosregs.h.al, dosregs.h.ah);
            exit(0);
    }
    if ( (long int) (ep = findmast(&len)) )
    {
        esv = malloc(len);
        if (addpath(ep, esv, len, argv[1]))
            printf("Failed to update Master Environment table (insufficient space)\n");
    }
    else
        printf("Cannot locate Master Environment table\n");
}




Robert Cawley             rjc@atom.oz.au
ANSTO