get the values for each line in the file in c - c

Question

I need to read this main.txt file:
STUDENT ID 126345
TEACHER MATH CLASS 122
And i need to get each values from this file . If this main.txt file was like this:
STUDENT ID 126345
TEACHER ID 3654432
I could do it like this:
#include <stdio.h>
int main(){
FILE *ptr_file;
int id;
char string1[100],string2[100];
ptr_file = fopen("main.txt","r");
while(fscanf(ptr_file,"%s %s %d",string1,string2,id) != EOF){
}
}
But I can't use fscanf() function because space amount between these values is not equal for each line. How can i get every value in line by line like this code ?

Answer 1

If every line has 3 values separated by empty spaces (or tabs), then
fscanf(ptr_file,"%s %s %d",string1,string2,&id);
is OK (and note that I used &id instead of id), because %s matches a sequence of non-white-space characters, so it
doesn't matter how many empty spaces are between the values, %s will consume
the empty spaces:
#include <stdio.h>
int main(void)
{
const char *v = "STUDENT \t ID \t 126345";
int id;
char string1[100],string2[100];
sscanf(v, "%s %s %d", string1, string2, &id);
printf("'%s' '%s' %d\n", string1, string2, id);
return 0;
}
which prints
$ ./a
'STUDENT' 'ID' 126345
In general the most robost solution would be to read line by line with fgets
and parse the line with sscanf as you have more control over when a line has a
wrong format:
char buffer[1024];
while(fgets(buffer, sizeof buffer, stdin))
{
int id;
char string1[100],string2[100];
if(sscanf(buffer, "%99s %99s %d", string1, string2, &id) != 3)
{
fprintf(stderr, "Line with wrong format\n");
break;
}
// do something with read values
}
edit
User Weather Vane points out that the line might have 3 or 4 values, then you
could do this:
char buffer[1024];
while(fgets(buffer, sizeof buffer, stdin))
{
int id;
char string1[100],string2[100],string3[100];
res = sscanf(buffer, "%99s %99s %99s %d", string1, string2, string3, &id);
if(res != 4)
{
int res = sscanf(buffer, "%99s %99s %d", string1, string2, &id);
if(res != 3)
{
fprintf(stderr, "Line with wrong format, 3 or 4 values expected\n");
break;
}
}
if(res == 3)
printf("'%s' '%s' %d\n", string1, string2, id);
else
printf("'%s' '%s' '%s' %d\n", string1, string2, string3, id);
}