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C: 13. File Handling

In programming, we may require some specific input data to be generated several numbers of times. Sometimes, it is not enough to only display the data on the console. The data to be displayed may be very large, and only a limited amount of data can be displayed on the console, and since the memory is volatile, it is impossible to recover the programmatically generated data again and again. However, if we need to do so, we may store it onto the local file system which is volatile and can be accessed every time. Here, comes the need of file handling in C.

File handling in C enables us to create, update, read, and delete the files stored on the local file system through our C program.

Writing File:-

#include <stdio.h>  
main(){  
   FILE *fp;  
   fp = fopen("file.txt", "w");//opening file  
   fprintf(fp, "Hello file by fprintf...\n");//writing data into file  
   fclose(fp);//closing file  
}  

Reading File:- 

#include <stdio.h>  
main(){  
   FILE *fp;  
   char buff[255];//creating char array to store data of file  
   fp = fopen("file.txt", "r");  
   while(fscanf(fp, "%s", buff)!=EOF){  
   printf("%s ", buff );  
   }  
   fclose(fp);  
}  

Example:- 
#include <stdio.h>  
void main()  
{  
    FILE *fptr;  
    int id;  
    char name[30];  
    float salary;  
    fptr = fopen("emp.txt", "w+");/*  open for writing */  
    if (fptr == NULL)  
    {  
        printf("File does not exists \n");  
        return;  
    }  
    printf("Enter the id\n");  
    scanf("%d", &id);  
    fprintf(fptr, "Id= %d\n", id);  
    printf("Enter the name \n");  
    scanf("%s", name);  
    fprintf(fptr, "Name= %s\n", name);  
    printf("Enter the salary\n");  
    scanf("%f", &salary);  
    fprintf(fptr, "Salary= %.2f\n", salary);  
    fclose(fptr);  
}  

Output:- 
Now open file from current directory. For windows operating system, go to TC\bin directory, you will see emp.txt file. It will have information.
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