fscanf in a structure which has a string - c

Question

I'm in trouble with my code.
I want to fscanf result.txt to structures, but it don't work;
result.txt format:
point name (for examples)
623 john
457 peter
312 chuck
etc.
First I count the lines then I malloc. For the structures' strings I have to malloc again, but I don't know the string's length. So I count it in the for loop.
#include <stdio.h>
#include <stdlib.h>
typedef struct ranklist {
int point;
char* name;
} ranklist;
int how_many_lines (FILE *fp){
rewind(fp);
int ch;
int line=0;
while (EOF != (ch = fgetc(fp)))
if (ch=='\n')
++line;
rewind(fp);
return line+1;
}
int how_many_letter(FILE *fp){
int ch;
int letter = 0;
int space=0;
while ('\n' != (ch = fgetc(fp)))
if (ch==' ')
space=1;
if (space == 1)
letter++;
return letter;
}
int main()
{
FILE *fp;
int y;
int name_length;
ranklist** r;
fp = fopen("result.txt","r");
int lines;
lines = how_many_lines(fp);
r = (ranklist**) malloc(lines * sizeof(ranklist*));
for (y = 0; y < lines; ++y){
name_length = how_many_letter(fp);
r[y] = (ranklist*) malloc(name_length * sizeof(ranklist));
}
for(y = 0; y < lines; y++){
fscanf(fp,"%d %s", &(r[y]->point), r[y]->name);
}
for( y = 0; y < lines; y++){
printf("%d %s", (r[y]->point), r[y]->name);
}
for (y = 0; y < lines; ++y)
free(r[y]);
free(r);
fclose(fp);
return 0;
}

Answer 1

sample to fix
int how_many_records(FILE *fp){
char ch;
int line=0;
int status;
rewind(fp);
while((status=fscanf(fp, "%*d %*[^\n]%c", &ch))==1)
++line;
if(status != EOF){
++line;
}
rewind(fp);
return line;
}
int how_many_letter(FILE *fp){
int letter = 0;
long pos = ftell(fp);
//fscanf(fp, " %*[^\n]%n", &letter);
fscanf(fp, " %*s%n", &letter);
fseek(fp, pos, SEEK_SET);
return letter;
}
int main(void){
FILE *fp = fopen("result.txt","r");
int y;
int name_length;
int lines = how_many_records(fp);
ranklist *r = malloc(lines * sizeof(*r));//just pointer, Do not need double pointer
for (y = 0; y < lines; ++y){
fscanf(fp, "%d", &r[y].point);
name_length = how_many_letter(fp);
r[y].name = malloc(name_length + 1);
fscanf(fp,"%s", r[y].name);
}
fclose(fp);
for( y = 0; y < lines; y++){
printf("%d %s\n", r[y].point, r[y].name);
free(r[y].name);
}
free(r);
return 0;
}

Answer 2

I did a few changes into your code and add some comments to explain. Just comment bellow any doubts.
int how_many_lines (FILE *fp){
rewind(fp);
int ch;
int line=0;
while (EOF != (ch = fgetc(fp)))
if (ch=='\n')
++line;
rewind(fp);
return line+1;
}
int how_many_letter(FILE *fp){
int ch;
int letter = 0;
// find first space since we
// know the input format <number> <name>
while ((ch = fgetc(fp)) != ' ');
// count the number of characters until end of file
// or '\n'
while ((ch = fgetc(fp)) != '\n' && ch != EOF )
letter++;
return (letter);
}
int main()
{
FILE *fp;
int y;
int name_length;
ranklist** r;
fp = fopen("file.txt","r");
int lines;
lines = how_many_lines(fp);
printf("[%d]\n", lines);
r = (ranklist**) malloc(lines * sizeof(ranklist*));
for (y = 0; y < lines; ++y){
name_length = how_many_letter(fp);
// you must allocate memory for ranklist element and string name
r[y] = (ranklist *) malloc(sizeof(ranklist));
r[y]->name = (char *) malloc(name_length * sizeof(char));
}
// rewind pointer again
rewind(fp);
for(y = 0; y < lines; y++){
fscanf(fp,"%d %s", &(r[y]->point), r[y]->name);
}
for( y = 0; y < lines; y++){
printf("%d %s\n", (r[y]->point), r[y]->name);
}
for (y = 0; y < lines; ++y)
free(r[y]);
free(r);
fclose(fp);
return 0;
}