After each printed line there are 2 blank lines

Question

I am trying to create a function which with read from a file some grades with the student names and print the grades in decreasing order. This is the function:

char studenteUN[50];
int punti;
int maxP = MAX_LNG;
int max = -1000;
int min = MAX_LNG;

FILE *ftemp = f;
while(fscanf(ftemp, "%s", studenteUN) != EOF){
  fscanf(ftemp, "%d", &punti);
  if(punti < min)
    min = punti;
}

while (maxP != min) {
  max = -1000;
  ftemp = muovi(f);
  while(fscanf(ftemp, "%s", studenteUN) != EOF){
    fscanf(ftemp, "%d", &punti);
    if(punti > max && punti < maxP)
      max = punti;
  }
  maxP = max;
  ftemp = muovi(f);
  while(fscanf(ftemp, "%s", studenteUN) != EOF){
    fscanf(ftemp, "%d", &punti);
    if(punti == max)
      printf("%s %d\n", studenteUN, punti);
  }
}

Te output is the following:

asdas 8


asdas 7


asdsa 6


andrea 5


asd 4


asd 1
asdsad 1


asdas 0
asd 0

I can not figure it out why this happens. The file I read from is the following:

2
1- askd a
   1- asd
   2- asd as
   3- asd as d
   4- asdas
   5- Non lo so.
1
2- asdsad asd as d
   1- asd a
   2- asd
   3- asd
   4- as df
   5- Non lo so.
2
andrea 5
asdsa 6
asdas 7
asd 1
asdas 0
asd 0
asdsad 1
asdas 8
asd 4

The muovi function:

FILE *muovi(FILE *f){
 fseek(f, 0, SEEK_SET);
 char resultato[MAX_LNG];
 int nD;
 fscanf(f, "%d", &nD);
 printf("\n");
 for(int i = 0; i <= nD*7;i++)
  fgets(resultato, MAX_LNG, f);
 return f;
}

Answer 1

I've written a demo sample: it reads input of the form 'name grade':

student1 1
student2 7
student3 -4
student4 11
student5 1111
student6 -11111

And outputs:

student5 1111
student4 11
student2 7
student1 1
student3 -4
student6 -11111

Here is the code behind, perhaps you can make an idea

#include <stdio.h>
#include <stdlib.h>

struct studs {
    int grade;
    char name[50];
};

int md_comparator(const void *v1, const void *v2)
{
    const struct studs *p1 = (struct studs *)v1;
    const struct studs *p2 = (struct studs *)v2;
    
    if (p1->grade < p2->grade)
        return 1;
    else if (p1->grade > p2->grade)
        return -1;
    else
        return 0;
}


int main()
{
    struct studs students[1000];
    struct studs temp;
    
    //read all students into students[] array
    int idx = 0;
    for (; fscanf(stdin, "%s %d", temp.name, &temp.grade) == 2; students[idx++] = temp)
        ;
    
    //sort descending, with the help of qsort and md_comparator function above
    qsort(students, idx, sizeof(students[0]), md_comparator);
    
    //print
    for (int i = 0; i < idx; i++)
        printf("%s %d\n", students[i].name, students[i].grade);
    
    return 0;
}

Answer 2

When reading lines of data from a file, you want to use a line-oriented input function such as fgets() or POSIX getline(). This ensures a complete line of input is consumed during each read. Otherwise when looking for a pattern, like a string followed by an integer, partial reads will likely lead to false-matches depending on what parts of the line are left in the input-buffer unread.

After reading each line into a buffer, you can simply parse the needed information from each line using sscanf() instead of your attempt to both read and parse with fscanf().

Putting that together, it is no problem at all to read and isolate only the student name and number from the file, e.g.

#include <stdio.h>
#include <stdlib.h>

#define NAMC 50         /* if you need a constant, #define one (or more) */
#define MAXC 1024

typedef struct {        /* struct for student name and number */
    char name[NAMC];
    int no;
} student;

int cmpstd (const void *a, const void *b)   /* qsort descending by student.no */
{
    const student *pa = a, *pb = b;
    
    return (pa->no < pb->no) - (pa->no > pb->no);
}

int main (int argc, char **argv) {
    
    student std[NAMC];      /* array of student */
    char buf[MAXC];         /* buffer to hold line */
    int n = 0;              /* student counter */
    /* use filename provided as 1st argument (stdin by default) */
    FILE *fp = argc > 1 ? fopen (argv[1], "r") : stdin;
    
    if (!fp) {  /* validate file open for reading */
        perror ("file open failed");
        return 1;
    }
    
    while (n < NAMC && fgets (buf, MAXC, fp)) { /* limit to array sz, read line */
        student tmp;        /* temporary struct for student */
        /* parse name and number from line, validating return */
        if (sscanf (buf, "%s %d", tmp.name, &tmp.no) == 2)
            std[n++] = tmp; /* add to array */
    }
    
    if (fp != stdin)   /* close file if not stdin */
        fclose (fp);
    
    qsort (std, n, sizeof *std, cmpstd);    /* sort by student.no descending */
    
    for (int i = 0; i < n; i++)             /* output results */
        printf ("%-10s %d\n", std[i].name, std[i].no);
}

Example Use/Output

With your input file in dat/prefixedstd.txt you would receive the following:

$ ./bin/read_prefixstd dat/prefixedstd.txt
asdas      8
asdas      7
asdsa      6
andrea     5
asd        4
asd        1
asdsad     1
asdas      0
asd        0

Look things over and let me know if you have further questions.