File Handling in C with examples | File Operations in C

File handling in C language is the process of storing, updating, retrieving, deleting data from a file using a C program.

A file, as we all know, is a container for information. The files are kept on a secondary storage device. The file can keep the information forever if the secondary storage device is protected.

File handling in C allows us to use C program for creating, updating, reading, and deleting files. On a file, you can perform the following operations.

• New file creation
• Open existing file
• Read from file
• Write to file
• Delete file

Types of files to process in C program

1. Text files
2. Binary Files

What is difference between text and binary files? Using a basic text editor, we create a text file with the .txt extension. Binary files hold data and information in a binary format of 0s and 1s. The application creates binary files with the.bin extension, which substitutes for the lack of text files in the program.

File handling Functions in c with examples

To open, read, write more data, create a new file, close or delete a file, search for a file, and so on, the C language offers us with a number of functions.

#	Functions	Description
1	fopen()	Open a file, either an existing one or a new one.
2	fprintf()	Adding data to a file that is already open.
3	fscanf()	Reads data from the file.
4	fputc()	Writes any character into the file.
6	fgetc()	Reads any character from the file.
7	fclose()	Closing a opened file.
8	fseek()	This function is used to move the file pointer to the desired location.
9	fputw()	Writes an integer value to file.
10	fgetw()	Reads an integer value to file.
11	ftell()	Checks the file’s current status.
12	rewind()	Sets a desired file pointer to the start of the file.

Opening a File in the Program – File: fopen()

To read, write, or update the file, we must first open it. The fopen() method is used to open a file in a C program.

FILE *fopen( const char * <file-name>, const char * mode );  

fopen("E:\\geekcer\\tfile.txt","w");
fopen("E:\\geekcer\\bfile.bin","rb");

How to create a file in C?

To create a file in C you need to specify the file name and opening mode in fopen() function. The file is created and then opened if the file does not exist. f a file already available on the system, this fopen() method opens file directly.

FILE *file;
file = fopen("<file-name>", "<opening-mode>");

File opening modes in C

Let’s have a look at some additional C program opening modes:

#	Model	Description
1	r	Opens a text file for reading only.
2	w	Opens a text file for writing.
3	r+	Allows you to read and write to a text file.
4	w+	Allows you to read and write to a text file.
5	a	Opening a file to append the content.
6	a+	Opening a file to append and reading data.
7	rb	Opening a binary file in read mode.
8	rb+	Opening a binary file in read and write mode.
9	wb	Opening a binary file in write mode.
10	wb+	Opening a binary file in reading and writing mode.
11	ab	Opening a binary file in append mode.
12	ab+	Opening a binary file in reading and append mode.

Program to open a file in read mode

FILE * fp;
fp = fopen("<file-name>", "r");

#include 
int main() {
  FILE * fp;
  fp = fopen("file.txt", "r");
  if (fp == NULL) {
    printf("File is not available, please check!\n");
  }
  fclose(fp);
  return 0;
}

Write a program to display the contents of a file on the screen

#include 
int main() {
  FILE * fp;
  int c;
  fp = fopen("file.txt", "r");
  c = getc(fp);
  while (c != EOF) {
    putchar(c);
    c = getc(fp);
  }
  fclose(fp);
  return 0;
}

Output:
Hello, Welcome to C Programming Language.

C program to open a file in write mode

FILE * fp;
fp = fopen("<file-name>", "w");

#include 
int main() {
  FILE * file;
  /* Opening the file in write mode */
  file = fopen("file.txt", "w");
  /* Write string to opened file */
  fprintf(file, "%s", "Example of writing content into file.");
  /* Closing the file */
  fclose(file);
  return 0;
}

C program to open a file in append mode

FILE * fp;
fp = fopen("<file-name>", "a");

#include 
int main() {
  FILE * fp;
  fp = fopen("file.txt", "a");
  fprintf(fp, "%s", "The appended content.");
  fclose(fp);
  return 0;
}