Category : Assembly Language Source Code
Archive   : UNDOC2E.ZIP
Filename : UNDOC.C

/*
* Program Description:
* This programs shows the usage of the undocumented DOS interrupt
* 2eh. By executing this interrupt, you can permanently modify the
* DOS environment variables.
*
* Compilation:
* CL /c /Ox /Zp /Gs /AS undoc.c
*
* Linking:
* LINK undoc+int2e;
*
* Execution:
* UNDOC env-variable=new-value
* where env-variable is the variable to set
* new-value is the new value of the environment variable
*
* Example: UNDOC PATH=C:\DOS
*/

/*
* make sure we use the standard functions properly
* by including function prototypes for common routines
*/
#include
#include
#include

/*
* make a prototype for int_2e()
*/
extern void int_2e(char *);

/*
* this string holds the command to execute via int 2eh
*/
static char command_to_execute[129];

/*
* main program entry point
*/
main(int argc, char *argv[])
{

/*
* if the user doesn't know how to use this utility, tough shit . . .
*/
if (argc != 2)
{
printf("Syntax error\n");
exit(1);
}

/*
* see if we are running under small model
*/
if (sizeof(char *) != sizeof(int))
{
printf("Only works under small model!\n");
exit(1);
}

/*
* byte zero needs the string length of the command
*/
command_to_execute[0] = strlen(argv[1]) + 5;
strcpy(&command_to_execute[1],"SET ");
strcat(command_to_execute,argv[1]);

/*
* we need to terminate the string with a
*/
command_to_execute[command_to_execute[0]+1] = 0x0d;

/*
* call the undocumented interrupt
*/
int_2e(command_to_execute);

/*
* terminate program
*/
exit(0);

}