CODEWITHSUNDEEP
cfile-io
Ary Silna
Ary Silna

Reputation: 17

Read text from file but it displays incorrectly

I'm using C for reading text from file and store it in array of struct. But after I print it using printf, it's output is not what i expected.

My Code:

#include<stdio.h>
struct userINFO {
    char id[6];
    char name[20];
    char lastName[20];
};
int main()
{
    FILE *fdata;
    struct userINFO allUser[3];
    int i=0;
    fdata = fopen("textdata.txt","r");

    if (fdata == NULL)
    {
        printf("ERROR!");
        return 0;
    }

    while (fscanf(fdata,"%s %s %s", allUser[i].id, allUser[i].name, allUser[i].lastName)!=EOF)
    {
        i++;
    }

    for (i = 0; i < 3 ; i++)
    {
        printf("ID: %s\n", allUser[i].id);
        printf("Name: %s\n", allUser[i].name);
        printf("LastName: %s\n", allUser[i].lastName);
    }
    fclose(fdata);

    return 0;
}

Text File:

001001
Firstname1
LastName1
601002
Firstname2
LastName2
601003
Firstname3
LastName3

Output

ID: 001001Firstname1
Name: Firstname1
LastName: LastName1
ID: 601002Firstname2
Name: Firstname2
LastName: LastName2
ID: 601003Firstname3
Name: Firstname3
LastName: LastName3

What it should be:

ID: 001001
Name: Firstname1
LastName: LastName1
ID: 601002
Name: Firstname2
LastName: LastName2
ID: 601003
Name: Firstname3
LastName: LastName3

I have tried many thing like change fscanf -> fgets, add %6s in printf, change text format etc. But its output still be the same. What should i change in my code to make it display correctly?

Upvotes: 0

Views: 47

Answers (2)

Ritwik Bhar
Ritwik Bhar

Reputation: 284

In the struct you are using an string of length 6 but you need to take in consideration the '\0' character. So making the id length as 7 will solve your problem

#include<stdio.h>
struct userINFO {
    char id[7];
    char name[20];
    char lastName[20];
};
int main()
{
    FILE *fdata;
    struct userINFO allUser[3];
    int i=0;
    fdata = fopen("textdata.txt","r");

    if (fdata == NULL)
    {
        printf("ERROR!");
        return 0;
    }

    while (fscanf(fdata,"%s %s %s", allUser[i].id, allUser[i].name, allUser[i].lastName)!=EOF)
    {
        i++;
    }

    for (i = 0; i < 3 ; i++)
    {
        printf("ID: %s\n", allUser[i].id);
        printf("Name: %s\n", allUser[i].name);
        printf("LastName: %s\n", allUser[i].lastName);
    }
    fclose(fdata);

    return 0;
}

Upvotes: 1

klutt
klutt

Reputation: 31296

Simple. Change:

struct userINFO {
    char id[6];
    char name[20];
    char lastName[20];
};

to

struct userINFO {
    char id[7];
    char name[20];
    char lastName[20];
};

In C, you need one extra character for a \0 that indicates the end of the string.

C is pretty lowlevel, so printf does not know how much memory that is reserved for a string. The only thing printf knows is where it starts. It then continue to read until it hits \0. If it reads outside the array it causes undefined behavior.

Upvotes: 0

Related Questions