file handling in c | Sharp Tutorial

Introduction

C Programming

C Advanced

Important C Programs

File Handling

To work with Files pointer variable of FILE type has to be declared like following:
FILE *fp;
The following operations may be performed on a File:

Create a new file
Open an existing file
Close a file
Read from a given file.
Write into a file.

  Commonly used modes of opening a File;

  1 Read Mode:
      fp = fopen("filename","r")

  2 Write Mode:
      fp = fopen("filename","w").
     In this mode, if file does not exists new file is created, and old content is replaced if file exist.

  3 Append Mode:
      fp = fopen("filename","a")
     In this mode, new content is appended with the old content of the file.

Program to Read the contents of a File and print it Back .

#include <stdio.h>
#include <conio.h>
void main()
{
    int num;
    FILE *fp;
    char ch;
    int noc=0;

    fp = fopen("test.c","r");
// Full path to open a file as below
//fp = fopen("D:\\TestFolder\\test.txt","r");
       
    if(fp == NULL)
      {
         printf("File not exist");
         exit(1);
       }
    else
      {
          ch=fgetc(fp);
          while(ch!=EOF)
             {
                 printf("%c", ch);
                 ch=fgetc(fp);
                 noc++;
              }
printf("\n no of characters in the file=%d",noc);
        }
       }// end of main

Program to Copy the contents of a File to another File .

#include <stdio.h>
#include <conio.h>
void main()
{
    int num;
    FILE *fp, *fp1;
    char ch;
    fp = fopen("test.c","r");
    fp1 = fopen("writefile.c","w");
      
    if(fp == NULL)
     {
        printf("File not exist"); 
        exit(1); 
      }
    else
     {
        ch=fgetc(fp); 
        while(ch!=EOF)
           {
               fputc(ch, fp1);
               ch=fgetc(fp);
           } 
      }
   fclose(fp);
   fclose(fp1);
}