C File Operations

C File Operations – Open, Close, Read & Write Files

In C, file operations allow you to perform tasks like opening, reading, writing, and closing files. You use file pointers and various standard functions from <stdio.h>.

🔹 fopen() and fclose()

fopen() is used to open a file, and fclose() is used to close it. Always close a file after use.

📝 Example: Open and Close File

#include <stdio.h>

int main() {
    FILE *fp = fopen("demo.txt", "w");
    
    if (fp == NULL) {
        printf("Unable to open file!\n");
        return 1;
    }

    fprintf(fp, "Hello, file operations in C!\n");
    fclose(fp);

    printf("File written and closed successfully.\n");
    return 0;
}

Try It Now

🔹 fputc() and fgetc()

fputc() writes a single character to a file, and fgetc() reads a character from a file.

📝 Example: Write and Read Characters

#include <stdio.h>

int main() {
    FILE *fp;

    // Writing to file
    fp = fopen("letters.txt", "w");
    fputc('A', fp);
    fputc('B', fp);
    fclose(fp);

    // Reading from file
    fp = fopen("letters.txt", "r");
    char ch;

    while ((ch = fgetc(fp)) != EOF) {
        printf("Char read: %c\n", ch);
    }

    fclose(fp);
    return 0;
}

Try It Now

🔹 feof() – Detecting End of File

The feof() function returns true when the end of a file is reached.

📝 Example: Using feof()

#include <stdio.h>

int main() {
    FILE *fp = fopen("letters.txt", "r");
    char ch;

    if (fp == NULL) {
        printf("File not found!\n");
        return 1;
    }

    while (!feof(fp)) {
        ch = fgetc(fp);
        if (ch != EOF)
            printf("%c ", ch);
    }

    fclose(fp);
    return 0;
}

Try It Now

🎯 Summary of File Functions

  • fopen() – Opens a file
  • fclose() – Closes a file
  • fputc() – Writes a character
  • fgetc() – Reads a character
  • feof() – Checks end-of-file

💡 Practice Challenge

Create a file, write a few characters using fputc(), then reopen it and read using fgetc(). Try adding your name letter-by-letter!