Opening and closing files - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to open a file named "data.txt" for reading.

C

#include <stdio.h>

int main() {
    FILE *file = fopen("data.txt", "[1]");
    if (file == NULL) {
        perror("Error opening file");
        return 1;
    }
    fclose(file);
    return 0;
}

Drag options to blanks, or click blank then click option'

Ar

Ba

Cx

Dw

Attempts:

3 left

💡 Hint

Common Mistakes

Using "w" which opens the file for writing and truncates it.

Using "a" which opens the file for appending.

Using "x" which creates a new file but fails if it exists.

The mode "r" opens the file for reading. If the file does not exist, fopen returns NULL.

2fill in blank

medium

Complete the code to close the opened file pointer named "fp".

C

#include <stdio.h>

int main() {
    FILE *fp = fopen("log.txt", "w");
    if (fp == NULL) {
        return 1;
    }
    // Write something to the file
    fprintf(fp, "Hello, file!\n");
    [1](fp);
    return 0;
}

Drag options to blanks, or click blank then click option'

Afopen

Bclose

Copen

Dfclose

Attempts:

3 left

💡 Hint

Common Mistakes

Using close(fp) which is not a standard C function for FILE pointers.

Using fopen(fp) which opens files, not closes.

Using open(fp) which is a system call, not for FILE pointers.

The function fclose(fp) closes the file associated with the file pointer fp.

3fill in blank

hard

Fix the error in the code to open a file for appending text.

C

#include <stdio.h>

int main() {
    FILE *file = fopen("output.txt", "[1]");
    if (file == NULL) {
        perror("Failed to open file");
        return 1;
    }
    fprintf(file, "Appending this line.\n");
    fclose(file);
    return 0;
}

Drag options to blanks, or click blank then click option'

Ar

Bw

Ca

Drw

Attempts:

3 left

💡 Hint

Common Mistakes

Using "r" which opens for reading only.

Using "w" which truncates the file.

Using "rw" which is not a valid mode string.

The mode "a" opens the file for appending. It writes data at the end of the file without truncating it.

4fill in blank

hard

Fill both blanks to open a file for writing and check if it opened successfully.

C

#include <stdio.h>

int main() {
    FILE *fp = fopen("test.txt", "[1]");
    if (fp == [2]) {
        perror("Cannot open file");
        return 1;
    }
    fclose(fp);
    return 0;
}

Drag options to blanks, or click blank then click option'

Aw

Br

CNULL

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using "r" mode which opens for reading, not writing.

Checking if fp equals 0 instead of NULL.

Using wrong mode strings.

Use "w" to open the file for writing. fopen returns NULL if it fails to open the file.

5fill in blank

hard

Fill all three blanks to open a file for reading, check for errors, and close it.

C

#include <stdio.h>

int main() {
    FILE *file = fopen("input.txt", "[1]");
    if (file == [2]) {
        perror("Error opening file");
        return 1;
    }
    // File operations here
    [3](file);
    return 0;
}

Drag options to blanks, or click blank then click option'

Aw

BNULL

Cfclose

Dr

Attempts:

3 left

💡 Hint

Common Mistakes

Using "w" mode which overwrites the file.

Checking if file pointer equals 0 instead of NULL.

Forgetting to close the file.

Open the file with mode "r" for reading. Check if the file pointer is NULL to detect errors. Use fclose to close the file.