c - Read in of a specific amount of variables -

i have read in different coordinates , save them struct. task can use

#include <stdio.h> #include <stdbool.h> 

and scanf read in. have use gcc compiler. 1 struct need 4 coordinates, insert can this:

coordinates: 11 12 13 14 21 22 23 24 //           | first   |  | second | 

for read in have following structure:

int read() {     int a;     scanf("%d",&a);     return a; } 

main:

printf("coordinates: "); int buffer = read(); while(buffer != 0) {     //write current buffer in struct     ...     buffer = read(); } 

so problem is, structure insert needs end 0. task is, read in procedure ends when there no more "foursome pack" of coordinates. example:

coordinates: 11 12 13 14 21 22 23 24 31 //            | first  |  | second |  invalid -> while loop ends 

so dont know how cancel while loop, because dont know how coordinates user feed in.

permissible library functionalities: scanf(), printf(), putchar().

i hope of understand me , can me.

op's code fails distinguish between read "0" , encountering error. not keep track of reading how many of 4 numbers read. not detect prefix "coordinates:"

int read() {     int a;     scanf("%d",&a);     return a; } 

---

read in "fourpack", 1 fourpack @ time.

struct pt4 {   int i[4]; };  // return eof, 0, 1, or 4 struct pt *read_foursome(struct pt4 *fourpack, int count) {   // prefix   if (count == 0) {     // record number of characters read     int n = 0;     if (scanf(" coordinates:%n", &n) == eof) return eof;     if (n == 0) return 1; // unexpected data, prefix not there.   }   // record number of fields successful scanned.   int n = scanf("%d%d%d%d",        &fourpack.i[0], &fourpack.i[1], &fourpack.i[2], &fourpack.i[3]);    // no more data   if (n == eof) return eof;      // no numeric  data   if (n == 0) return 0;    // unexpected data   if (n != 4) return 1;    // expected   return 4; } 

sample usage

int n; int count = 0;   struct pt4 fourpack; printf("coordinates:");  while ((n = read_foursome(&fourpack, count)) == 4) {   // use fourpack   printf(" %d %d %d %d",        fourpack.i[0], fourpack.i[1], fourpack.i[2], fourpack.i[3]);   count++; } printf("\n");   // if n == 0 maybe time line of fourpack // if n == 1, syntax error in line.