File Handling in C

File handling in C allows you to work with files on your computer's storage. It enables reading data from files, writing data to files, and performing other file-related operations. The standard library provides functions and types for file handling in C.

Here are the basic steps involved in file handling in C:

1. File Pointer

  • To work with files, you need to declare a file pointer of type FILE.
  • The file pointer will hold the address of the file you want to read from or write to.

Syntax

FILE *file_pointer;

Example

FILE *fp;

2. Opening a File

  • Before reading from or writing to a file, you need to open it using the fopen() function.
  • The fopen() function takes two arguments: the file name (or path) and the mode.

Syntax

file_pointer = fopen(file_name, mode);

Example

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

Common file modes:

  • "r": Read mode
  • "w": Write mode (creates a new file or overwrites an existing file)
  • "a": Append mode (appends data to an existing file or creates a new file)
  • "r+": Read and write mode

3. Reading from a File:

  • To read data from a file, you can use functions like fscanf() or fgets().
  • fscanf() reads formatted data, while fgets() reads a line of text.

Example using fscanf():

int num;
fscanf(fp, "%d", &num);  // Reads an integer from the file

Example using fgets():

char line[100];
fgets(line, sizeof(line), fp);  // Reads a line of text from the file

4. Writing to a File:

  • To write data to a file, you can use functions like fprintf() or fputs().
  • fprintf() writes formatted data, while fputs() writes a string.

Example using fprintf():

int num = 42;
fprintf(fp, "%d\n", num);  // Writes the value of num to the file

Example using fputs():

char message[] = "Hello, world!";
fputs(message, fp);  // Writes the string to the file

5. Closing a File:

  • After you finish working with a file, it is important to close it using the fclose() function.
  • Closing the file ensures that all data is written and releases system resources.

Syntax

fclose(file_pointer);

Example

fclose(fp);  // Closes the file

File handling in C allows you to perform various operations on files, such as reading data, writing data, modifying file contents, and more. It is essential to handle file-related errors and check if file operations are successful before proceeding. Additionally, you should always close files properly to avoid resource leaks.

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