Bdtjtk

So there's a file I'm using fscanf() in. I've set a condition in my code that when (fscanf(...) == EOF, the program needs to break out of the function I'm currently in. The thing is, this condition is never satisfied in any of the cases where there's no more lines of text in the file. EOF is always -1, whereas fscanf(...) returns 4 each time there's a line of code, and 3 when there's nothing left for it to search through (instead of -1). If I add a line of code similar to the other ones, I will simply get one more instance of fscanf() returning 4, and then again, it'll give me a 3.

What could possibly be the issue? Thank you in advance!

Sample text file content:

CHRISTOU GIORGOS,140,VAS. OLGAS 112

MALAKOU MALAKOS,150,DRAS. BAGAS 12

TSIKOU GIJRAN,140,JABS. DRALGAS 1

TSIKOU BIRBAN,140,JABS. DRALGAS 1

DELHDHMHTRIOU SPYROS,50,SPEED. BAGAS 62

FOX SIN,40,BAN. NINJA 1

Code:

#include <stdio.h>

#define M 100



typedef struct {

    char name[30];

    int apousies;

} studentT;



void readInput (FILE* infile, studentT students, int *pApousies, int *pStudents);





int main()

{

    char inputfilename[30];

    FILE* infile;



    while (1) {

        printf("Input file name :");

        gets(inputfilename);



        infile  = fopen(inputfilename, "r");



        if (infile != NULL) break;

        printf("Cannot open input file %s. Try again.n", inputfilename);

    }



    studentT students[M];

    int numberOfStudents = 0, numberOfApousies = 0;

    readInput(infile, students, &numberOfApousies, &numberOfStudents);

    fclose(infile);

    return 0;

}



void readInput (FILE* infile, studentT students, int *pApousies, int *pStudents)

{

    int nscan, apousies, studcount, apouscount, line;

    char name[30], comments[68], termch;



    line = 0;

    while (1)

    {

        nscan = fscanf(infile, "%30[^,], %d, %68[^n]%c", name, &apousies, comments, &termch);

       /* printf("onoma: %s apousies: %d sxolia: %s terma: %cn", name, apousies, comments, termch);

        printf("%dn", nscan);

        printf("%dn", EOF);*/

        if (nscan == EOF) break; 

        line++;



        if (nscan != 4 || termch != 'n')

        {

            printf("Error in line %d. Program terminationn", line);

            exit(1);

        }

    }

}

fscanf returns 3 instead of -1 (EOF) at the end of the file

Because the last line lacks a 'n'.

OP's code "works" with the "tmp.txt" the below code makes.

fscanf() is hard to use right. Easier to code and debug with fgets(). Discussion follows.

"%30[^,]" allows too much for char name[30]. Use char name[30+1] or "%29[^,]"

OP's approach can readily fail with seemingly minor parsing problems such as a missing 'n' on the last line. After such a failure, recovery is extraordinary difficult with fscanf()

Debug: Importantly, the below print should not be attempted until code insures nscan >= 4

if (nscan >= 4) // add

  printf("onoma: %s apousies: %d sxolia: %s terma: %cn", name, apousies,  comments, termch);

Instead, use fgets(). With line orientated data, this really is the best first step.

fscanf() is challenging to use and cope with errors. Far simpler to read a line with fgets() and then parse.

Using " %n" is a nice way to detect if all the line parsed.

#include <stdio.h>

#include <stdlib.h>

#define M 100



typedef struct {

  char name[30];

  int apousies;

} studentT;



void readInput(FILE* infile, studentT students, int *pApousies,

    int *pStudents) {

  (void) students;

  (void) pApousies;

  (void) pStudents;

  int line = 0;

  char buf[200];

  while (fgets(buf, sizeof buf, infile)) {

    int apousies;

    char name[30], comments[68];

    int n = 0;



    line++;

    sscanf(buf, " %29[^,],%d , %67[^n] %n", name, &apousies, comments, &n);

    if (n == 0 || buf[n]) {

      fprintf(stderr, "Error in line %d <%s>. Program terminationn", line, buf);

      exit(1);

    }

    printf("Success %d <%s> %d <%s>n", line, name, apousies, comments);

  }

}

Sample use

int main() {

  FILE *f = fopen("tmp.txt", "w");

  fputs("CHRISTOU GIORGOS,140,VAS. OLGAS 112n"

      "MALAKOU MALAKOS,150,DRAS. BAGAS 12n"

      "TSIKOU GIJRAN,140,JABS. DRALGAS 1n"

      "TSIKOU BIRBAN,140,JABS. DRALGAS 1n"

      "DELHDHMHTRIOU SPYROS,50,SPEED. BAGAS 62n"

      "FOX SIN,40,BAN. NINJA 1n", f);

  fclose(f);



  f = fopen("tmp.txt", "r");

  studentT st[M];

  readInput(f, st, NULL, NULL);

  fclose(f);

}

Output

Success 1 <CHRISTOU GIORGOS> 140 <VAS. OLGAS 112>

Success 2 <MALAKOU MALAKOS> 150 <DRAS. BAGAS 12>

Success 3 <TSIKOU GIJRAN> 140 <JABS. DRALGAS 1>

Success 4 <TSIKOU BIRBAN> 140 <JABS. DRALGAS 1>

Success 5 <DELHDHMHTRIOU SPYROS> 50 <SPEED. BAGAS 62>

Success 6 <FOX SIN> 40 <BAN. NINJA 1>