1 #include <stdio.h>

     2 #include <stdlib.h>

     3 #include <string.h>

     4 

     5 // for installation notes see C0.c

     6 // this program can be called with

     7 //

     8 //  ./args2-good | ./C2

     9 //

    10 // or

    11 //

    12 // ./args2-bad | ./C2

    13 

    14 

    15 int match(char *s1, char *s2) {

    16   while( *s1 != '\0' && *s2 != 0 && *s1 == *s2 ){

    17     s1++; s2++;

    18   }

    19   return( *s1 - *s2 );

    20 }

    21 

    22 // since gets() is insecure and produces lots of warnings, 

    23 // I use my own input function instead ;o)

    24 char ch;

    25 int i;

    26 

    27 void get_line(char *dst) {

    28   char buffer[8];

    29   i = 0;

    30   while ((ch = getchar()) != '\n') {

    31     buffer[i++] = ch; 

    32   }

    33   buffer[i] = '\0';

    34   strcpy(dst, buffer);

    35 }

    36 

    37 void welcome() { printf("Welcome to the Machine!\n"); exit(0); }

    38 void goodbye() { printf("Invalid identity, exiting!\n"); exit(1); }

    39 

    40 main(){

    41   char name[8];

    42   char pw[8]; 

    43 

    44   printf("login: "); 

    45   get_line(name);

    46   printf("password: "); 

    47   get_line(pw);

    48 

    49   if(match(name, pw) == 0)

    50     welcome();

    51   else

    52     goodbye();

    53 }

    54