rewind() in C

In C Language, rewind() is a standard library function used to reset the file position indicator to the beginning of a file.

It is equivalent to calling "fseek()" with an offset of 0 bytes from the beginning of the file.

Syntax:

void rewind(FILE *stream);

"stream": Pointer to a "FILE" object that identifies the file.
The "rewind()" function does not return a value.

Reading a File Twice:

"rewind()" is used to reset the file position indicator so that the file can be read again.

Example:

Note: "rewind()" is called after the first loop to reset the file position indicator. Then, the file is read again from the beginning.

Example:

#include <stdio.h>

int main() {
    FILE *file;
    char ch;

    // Open the file in read mode
    file = fopen("example.txt", "r");

    // Check if file opened successfully
    if (file == NULL) {
        perror("Error opening file");
        return 1;
    }

    // Read and print characters from the file
    while ((ch = fgetc(file)) != EOF) {
        putchar(ch);
    }

    // Reset the file position indicator to the beginning of the file
    rewind(file);

    // Read and print characters from the beginning of the file again
    printf("\nReading from the beginning again:\n");
    while ((ch = fgetc(file)) != EOF) {
        putchar(ch);
    }

    // Close the file
    fclose(file);

    return 0;
}

Example:

#include <stdio.h>

int main() {
    FILE *file;

    // Open the file in write mode
    file = fopen("output.txt", "w");

    // Check if file opened successfully
    if (file == NULL) {
        perror("Error opening file");
        return 1;
    }

    // Write content to the file
    fprintf(file, "Hello, world!\n");

    // Reset the file position indicator to the beginning of the file
    rewind(file);

    // Read and print content from the file
    printf("Content of the file:\n");
    char ch;
    while ((ch = fgetc(file)) != EOF) {
        putchar(ch);
    }

    // Close the file
    fclose(file);

    return 0;
}

Resetting File Position Indicator after Writing:

"rewind()" is used to reset the file position indicator after writing to a file so that the written content can be read:

"rewind()" is used after writing to the file to reset the file position indicator. Then, the content of the file is read and printed to the console.

<-- fseek()

ftell() -->