Files is collection of records (or) it is a place on hard disk, where data is stored permanently. By using C commands, we access the files in different ways.
Need of files in C language
Entire data is lost when the program terminates and storing in a file will preserve your data even if the program terminates.
If you want to enter a large amount of data, normally, it takes a lot of time to enter them all.
If you have a file containing all the data, you can easily access the contents of the file by using few commands in C.
You can easily move your data from one computer to another without changes.
Operations on files
The operations that can be carried out on files in C language are as follows −
- Naming the file.
- Opening the file.
- Reading from the file.
- Writing into the file.
- Closing the file.
Syntax
The syntax for opening and naming file is as follows −
FILE *File pointer;
For example, FILE * fptr;
File pointer = fopen ("File name”, "mode”);For example, fptr = fopen ("sample.txt”, "r”)
FILE *fp;
fp = fopen ("sample.txt”, "w”);The syntax for reading from fileis as follows −
int fgetc( FILE * fp );// read a single character from a file
The syntax for writing into file is as follows −
int fputc( int c, FILE *fp ); // write individual characters to a stream
Example
Following is the C program to demonstrate the files −
#include<stdio.h>
void main(){
//Declaring File//
FILE *femp;
char empname[50];
int empnum;
float empsal;
char temp;
//Opening File and writing into it//
femp=fopen("Employee Details.txt","w");
//Writing User I/p into the file//
printf("Enter the name of employee : ");
gets(empname);
//scanf("%c",&temp);
printf("Enter the number of employee : ");
scanf("%d",&empnum);
printf("Enter the salary of employee : ");
scanf("%f",&empsal);
//Writing User I/p into the file//
fprintf(femp,"%s\n",empname);
fprintf(femp,"%d\n",empnum);
fprintf(femp,"%f\n",empsal);
//Closing the file//
fclose(femp);
//Opening File and reading from it//
femp=fopen("Employee Details.txt","r");
//Reading O/p from the file//
fscanf(femp,"%s",empname);
//fscanf(femp,"%d",&empnum);
//fscanf(femp,"%f",&empsal);
//Printing O/p//
printf("employee name is : %s\n",empname);
printf("employee number is : %d\n",empnum);
printf("employee salary is : %f\n",empsal);
//Closing File//
fclose(femp);
}Output
When the above program is executed, it produces the following result −
Enter the name of employee : Pinky Enter the number of employee : 20 Enter the salary of employee : 5000 employee name is : Pinky employee number is : 20 employee salary is : 5000.000000