File Handling in C

File Handling:

File is a collection of bytes that is stored on secondary storage devices like disk. There are two kinds of files in a system.

1.    Text files (ASCII)

2.    Binary files

·      Text files contain ASCII codes of digits, alphabetic and symbols.

·      Binary file contains collection of bytes (0’s and 1’s). Binary files are compiled version of text files.

Basic file operations in C programming:

There are 4 basic operations that can be performed on any files in C programming language. They are,

1.    Opening/Creating a file

2.    Closing a file

3.    Reading a file

4.    Writing in a file

fopen() –

            fopen() function is used to open a file to perform operations such as reading, writing etc. In a C program, we declare a file pointer and use fopen() as below. fopen() function creates a new file if the mentioned file name does not exist.

        FILE *fp;
        fp=fopen (“filename”, ”‘mode”);

       Where,
                fp – file pointer to the data type “FILE”.
                Filename – the actual file name with full path of the file.
                mode – refers to the operation that will be performed on the file. Example: r, w, a etc.

fclose() -

fclose() function closes the file that is being pointed by file pointer fp. In a C program, we close a file as below.
            fclose (fp);

fprintf() -

            The fprintf() function is same as printf() but instead of writing data to the console, it writes formatted data into the file. Almost all the arguments of fprintf() function is same as printf() function except it has an additional argument which is a file pointer to the file where the formatted output will be written.

            Syntax:-

                        fprintf(filepointer, data to be write on file)

            Example:-

                        fprintf(fp, "this is my file");

fscanf() -

The fscanf() function is used to read formatted input from the file. It works just like scanf() function. The main difference is that fscanf() function requires a file pointer.

            Syntax:-

                        fscanf(file pointer, data to be read from file)

            Example:-

                        fscanf(fp, "%s", sname);

Different File modes

Mode	Description
r	opens a text file in read mode
w	opens a text file in write mode
a	opens a text file in append mode
r+	opens a text file in read and write mode
w+	opens a text file in read and write mode
a+	opens a text file in read and write mode

Example 1 (Writing Data in File ):

#include<stdio.h>

#include<conio.h>

main()

{

FILE *fp;

fp=fopen("myfile.txt","w");//opening file

fprintf(fp,"This is my file");//writing data into file

fclose(fp);//closing file

getch();

}

Example 2 (Reading Data from File ):

#include <stdio.h> 

#include <conio.h> 

main()

{ 

  FILE *fp; 

  char data[50];//creating char array to store data of file 

  fp = fopen("myfile.txt", "r"); 

  while(fscanf(fp, "%s", data)!=EOF)

  { 

    printf("%s ", data ); 

  } 

  fclose(fp); 

  getch();

} 

Example 3 (Write operation on File ):

#include <stdio.h> 

#include <conio.h> 

void main() 

{ 

  FILE *fp; 

  int eid; 

  char ename[30]; 

  float salary; 

  fp = fopen("emp.txt", "w");/*  open for writing */ 

  printf("Enter the id\n"); 

  scanf("%d", &eid); 

  printf("Enter the name \n"); 

  scanf("%s", &ename); 

  printf("Enter the salary\n"); 

  scanf("%f", &salary); 

  fprintf(fp, "%d %s %f", eid, ename, salary); 

  fclose(fp); 

  getch();

} 

Example 4 (Read operation on File ):

#include <stdio.h> 

#include <conio.h> 

void main() 

{ 

  FILE *fp; 

  int eid; 

  char ename[30]; 

  float salary; 

  fp = fopen("emp.txt", "r");/*  open for writing */ 

  fscanf(fp, "%d %s %f", &eid, &ename, &salary); 

  printf("Enter the id is = %d\n", eid); 

  printf("Enter the name  is = %s\n",ename); 

  printf("Enter the salary = %f \n",salary); 

  fclose(fp); 

  getch();

}