/* Demonstration of error and EOF checking.  Attempts to read integers
   from lst10-3.dat.  Displays any line in error, and stops at EOF */

#include <stdio.h>  /* This contains the definition for the EOF macro */
#include <stdlib.h>
FILE * file_open(char name[], char access_mode[]);

main() {
    FILE * intfile;
    int intval, result;
    char buf[81];

    /* Open file with file_open from lst10-2 (not repeated for brevity) */
    intfile = file_open("lst10-3.dat", "r");

    /* Read first value, remembering the fscanf result. */
    result = fscanf(intfile, "%d", &intval);

    /* Loop as long as fscanf result is not EOF */
    while (result != EOF) {
        /* But perhaps fscanf hit an error (a non-integer in the file).
           Input the troublemaker as a string, and display. */
        if (result != 1) {   /* Since correct input assigns value 1 */
            /* Read the line as a string. */
            fgets(buf, 81, intfile);
            /* Display error message. */
            printf("fscanf result %d! Input was: \"%s\"\n", result, buf);
        } else {  /* Fscanf must have worked - just print the integer. */
            printf("fscanf result %d. Integer is %d\n", result, intval);
        }
        /* Input next value. */
        result = fscanf(intfile, "%d", &intval);
    }

    /* After the loop, let's find out what value fscanf returned. */
    printf("After last input, fscanf result was %d.\n", result);
    return 0;
}

FILE * file_open (char name[], char access_mode[]) {
    FILE * f;
    f = fopen (name, access_mode);
    if (f == NULL) { /* error? */
        /* Library function perror prints an informative message. */
        perror ("Cannot open file");
        exit (1);  /* Terminate after printing error message. */
    }
    return f;      /* Only happens if fopen succeeded. */
}