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Re: Setting DOS Environment Variables

by Rex(Wrecks) (Curate)
on Apr 20, 2004 at 18:20 UTC ( #346737=note: print w/replies, xml ) Need Help??

in reply to Setting DOS Environment Variables

Check this thread as I suspect this is what you are trying to do: SetEnviron.bat

"Nothing is sure but death and taxes" I say combine the two and its death to all taxes!

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Re: Re: Setting DOS Environment Variables
by DrHyde (Prior) on Apr 21, 2004 at 09:01 UTC
    An alternative approach would be to use this C code and some XS magic, or Inline::C. Assuming, of course, that getting a DOSsy perl and C to talk to each other is practical:
    /* Call the set() function with two pointers to char as the + parameters. The first points to the environment variable + NAME, the second to the VALUE. The NAME is made + upper-case automatically. */ #include <dos.h> #include <stdio.h> #include <string.h> #include <ctype.h> #include <conio.h> #define VLEN 80 #define BUFLEN 1000 unsigned int _psp; unsigned short peekw(); unsigned char peekb(); void pokeb(); set (char *varname, char *value) { unsigned short x, p, y, envsize, free; int found; char c, var[VLEN+BUFSIZ+1]; int i, varlen; varlen = strlen(varname); for (i=0; i <= varlen; i++) var[i] = toupper(varname[i]); strcat(var,"="); varlen++; p = _psp; do { x = p; p = peekw(x,0x16); } while (p != x); if (peekb(x-1,0) != 0x4d) { cputs("Wrong DOS segment - weirdness is occuring - PANIC!\n\01 +5"); exit(2); } p = peekw(x,0x2c); envsize = peekw(p-1, 3) << 4; x = 0; found = 0; do { if (mystrncmp(p,x,var,varlen) == 0) { y = x; found = 1; } while (c=peekb(p,x)) { if (found == 2) { pokeb(p,y,c); y++; } x++; } switch (found) { case 1: found=2; break; case 2: pokeb(p,y,c); y++; break; } } while (peekb(p,++x)); if (found) { pokeb(p,y,'\0'); x = y; } free = envsize - x - 1; for (i=2; i < strlen(value) + 2; i++) value[i] = tolower(value[i]) +; strcat(var,value); y = strlen(var); if (y+1 > free) { cputs("Sorry, your environment space is full, program abort.\n +\015"); cputs("Try \"shell=c:\ /p /e:62\" in config.sys to\ +n\015"); cputs("increase your environment space to 992 bytes\n\015"); exit(3); } for (i=0; i <= y; i++) pokeb(p, x++, var[i]); pokeb(p, x, 0); } mystrncmp(seg,offset,source,n) short seg,offset; int n; char *source; { int i, dif; for (i=0; i < n; i++) { dif = peekb(seg,offset+i) - source[i]; if (dif) return dif; }; return 0; } unsigned char peekb(seg,offset) short seg,offset; { char far *fptr; FP_SEG(fptr) = seg; FP_OFF(fptr) = offset; return *fptr; } void pokeb(seg,offset,what) short seg,offset; char what; { char far *fptr; FP_SEG(fptr) = seg; FP_OFF(fptr) = offset; *fptr = what; } unsigned short peekw(seg,offset) short seg,offset; { unsigned far *fptr; FP_SEG(fptr) = seg; FP_OFF(fptr) = offset; return *fptr; }
    Note that I have only used that with MS Quick C, it may or may not work with other compilers. No, I no longer have any idea how it works. There are probably cut n' paste errors. It may turn your cat into an almond. Caveat Programmer.

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