Reading file using fscanf() in C

Question

I need to read and print data from a file.
I wrote the program like below,

#include<stdio.h>
#include<conio.h>
int main(void)
{
char item[9], status;

FILE *fp;

if( (fp = fopen("D:\\Sample\\database.txt", "r+")) == NULL)
{
    printf("No such file\n");
    exit(1);
}  

 if (fp == NULL)
{
    printf("Error Reading File\n");
}

while(fscanf(fp,"%s %c",item,&status) == 1)  
{  
       printf("\n%s \t %c", item,status);  
}  
if(feof(fp))  
{            
         puts("EOF");     
}  
else  
{  
 puts("CAN NOT READ");  
}  
getch();  
return 0;  
}

the database.txt file contains
Test1 A
Test2 B
Test3 C

When I run the code, it prints

CAN NOT READ.

Please help me to find out the problem.

`fopen` can fail for many reasons. Printing `"No such file"` is not useful when there is a permissions error. `man perror` — William Pursell, Jun 08 '22 at 13:44

score 28 · Accepted Answer · answered Jul 28 '10 at 10:09

28

First of all, you're testing fp twice. so printf("Error Reading File\n"); never gets executed.

Then, the output of fscanf should be equal to 2 since you're reading two values.

answered Jul 28 '10 at 10:09

Hamid Nazari

3,905
2
28
31

Michael Foukarakis · Answer 2 · 2022-06-08T13:40:13.423

scanf() and friends return the number of input items successfully matched. For your code, that would be two or less (in case of less matches than specified). In short, be a little more careful with the manual pages:

#include <stdio.h>
#include <errno.h>
#include <stdbool.h>

int main (void) {
    FILE *fp;

    if ((fp = fopen("D:\\Sample\\database.txt", "r+")) == NULL) {
        puts("No such file\n");
        exit(1);
    }

    char item[9], status;
    while (true) {
        int ret = fscanf(fp, "%s %c", item, &status);
        if (ret == 2)
            printf("\n%s \t %c", item, status);
        else if (errno != 0) {
            perror("scanf:");
            break;
        } else if(ret == EOF) {
            break;
        } else {
            puts("No or partial match.\n");
        }
    }
    puts("\n");
    if (feof(fp)) {
        puts("EOF");
    }
    return 0;
}

It's equivalent to `while(1)` or in pseudocode `while(true)`. — Michael Foukarakis, Jul 28 '10 at 11:18

score 3 · Answer 3 · answered Jul 28 '10 at 10:10

3

In your code:

while(fscanf(fp,"%s %c",item,&status) == 1)

why 1 and not 2? The scanf functions return the number of objects read.

answered Jul 28 '10 at 10:10

score 1 · Answer 4 · answered Jul 28 '10 at 10:09

1

fscanf will treat 2 arguments, and thus return 2. Your while statement will be false, hence never displaying what has been read, plus as it has read only 1 line, if is not at EOF, resulting in what you see.

answered Jul 28 '10 at 10:09

Didier Trosset

36,376
13
83
122

Reading file using fscanf() in C

4 Answers4

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