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  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. #include <ctype.h>
  4.  
  5. static void skip_input(FILE *stream)
  6. {
  7.     int c;
  8.     do {
  9.         c = fgetc (stream);
  10.     } while (c != EOF && c != '\n');
  11. }
  12.  
  13. int main()
  14. {
  15.     int a;
  16.     int r;
  17.     char junk[2] = {'\0'};
  18.  
  19.     printf("Please enter a value: ");
  20.  
  21.     for (;;) {
  22.         r = scanf("%d%1[^\n]", &a, junk);
  23.  
  24.         if (r == EOF)
  25.             return EXIT_FAILURE;
  26.         if (r != 1) {
  27.             printf("Number must be numeric!\n");
  28.             skip_input(stdin);
  29.         } else if (a < 0) {
  30.             printf("Number must be postive\n");
  31.             skip_input(stdin);
  32.         } else {
  33.             printf("Everything is goood\n");
  34.             break;
  35.         }
  36.     }
  37.  
  38.     return EXIT_SUCCESS;
  39. }
Success #stdin #stdout 0.01s 1724KB
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stdin
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1a
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stdout
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Please enter a value: Number must be numeric!
Everything is goood
https://ideone.com/WqkJB
language:
C (gcc 8.3)
created:
11 years ago
visibility:
public

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