How to read data in a file using fscanf

Question

I have a table format in a file. I want to print it using fscanf. The table looks like this with 6 columns and 4 rows.

Name       Date          Opening    Amount     Type             Closing
Thiluxan   21.05.2015    8500       4500       Withdrawal       4000
Black      05.02.2014    7896       6548       Withdrawal       1348
Whitee     02.05.2015    8524       256394     Deposit          264918

FILE *file1;
file1 = fopen("Bank.txt","r");
while(fscanf(file1, "%s %s  %s  %s  %s  %s", text) != EOF ) {
    printf("%s\n", text);
}
fclose(file1);

The output doesn't show anything and it returns a blank screen

You have 6 formatting fields in your format string, but you're only writing to 1 variable `text`. That causes undefined behavior. — Barmar, Jul 31 '19 at 05:27
You want to *print* it with `fscanf`? Do you know what `fscanf` does? — David Schwartz, Jul 31 '19 at 05:29
related: [Reading file using fscanf() in C](https://stackoverflow.com/q/3351809/2513200) — Hulk, Jul 31 '19 at 05:37
The documentation of the `scanf` family of functions. Each formatting operator needs a corresponding variable to write to. — Barmar, Jul 31 '19 at 05:37
You can use `%*s` to specify that a field should be parsed but not written to a variable. — Barmar, Jul 31 '19 at 05:40
Ya thats a silly mistake i made. I failed to add 6 variables to save 6 data in a row. Thank you all for your solutions — , Jul 31 '19 at 05:42
@Barmar sorry misunderstanding on my part, I was thinking about something different. — n. m. could be an AI, Jul 31 '19 at 10:34

score 2 · Answer 1 · answered Jul 31 '19 at 05:52

As pointed out in answer and comments above, you need to provide six variables into the fscanf arguments. Also it would be better if you have a model for your data. I would suggest to use a struct and input all data into an array of structs, that way you would be able to manage it better rather than managing random variables.

#include <stdio.h>

typedef struct Bank {
    char name[100];
    char date[100];
    char opening[100];
    char amount[100];
    char type[100];
    char closing[100];
} Bank;

int main() {
    FILE *file1;
    file1 = fopen("Bank.txt","r");

    Bank bankList[100];
    int nCustomers = 0;
    while(fscanf(file1, "%s%s%s%s%s%s", bankList[nCustomers].name, bankList[nCustomers].date, bankList[nCustomers].opening, bankList[nCustomers].amount, bankList[nCustomers].type, bankList[nCustomers].closing) != EOF ){
            printf("%s %s %s\n", bankList[nCustomers].name, bankList[nCustomers].date, bankList[nCustomers].opening);
            nCustomers++;
    }
    fclose(file1);
}

score 1 · Answer 2 · answered Jul 31 '19 at 05:37

1

Your mistake is the number of variables you passed into fscanf. If you want to read 6 strings you need to provide 6 string variables to save in

Like So

FILE * file1;
file1 = fopen("Bank.txt", "r");
while (fscanf(file1, "%s %s  %s  %s  %s  %s", t1, t2, t3, t4, t5, t6) != EOF) {
    printf("%s %s %s %s %s %s\n", t1, t2, t3, t4, t5, t6);
}
fclose(file1);

You have to instantiate all ts of course

answered Jul 31 '19 at 05:37

Issam Rafihi

432
3
10

1

In addition to that, it would be a good idea to check the return value of `fopen` as well as ensuring that the return value of `fscanf` is the expected number of arguments, instead of just checking it is not `EOF`. – Hulk Jul 31 '19 at 05:48

How to read data in a file using fscanf

2 Answers2