If the file exists, its contents are overwritten. If the file
w+
writing.
does not exist, it will be created.
Open for both reading and
a+
If the file does not exists, it will be created.
appending.
Closing a File
The file should be closed after reading/writing of a file. Closing a file is performed using library function fclose().
fclose(ptr); //ptr is the file pointer associated with file to be closed.
The Functions fprintf() and fscanf() functions.
The functions fprintf() and fscanf() are the file version of printf() and fscanf(). The only difference while using fprintf()and fscanf() is that, the first argument is a pointer to the structure FILE
Writing to a file
#include <stdio.h>
int main()
{
int n;
FILE *fptr;
fptr=fopen("C:\\program.txt","w");
if(fptr==NULL){
printf("Error!");
exit(1);
}
printf("Enter n: ");
scanf("%d",&n);
fprintf(fptr,"%d",n);
fclose(fptr);
return 0;
}
This program takes the number from user and stores in file. After you compile and run this program, you can see a text file
program.txt created in C drive of your computer. When you open that file, you can see the integer you entered.
Similarly, fscanf() can be used to read data from file.
Reading from file
#include <stdio.h>
int main()
{
int n;
FILE *fptr;
if ((fptr=fopen("C:\\program.txt","r"))==NULL){
printf("Error! opening file");
exit(1); /* Program exits if file pointer returns NULL. */
}
fscanf(fptr,"%d",&n);
printf("Value of n=%d",n);
fclose(fptr);
return 0;
}
If you have run program above to write in file successfully, you can get the integer back entered in that program using this program.
Other functions like fgetchar(), fputc() etc. can be used in similar way.
Binary Files
Depending upon the way file is opened for processing, a file is classified into text file and binary file.
If a large amount of numerical data it to be stored, text mode will be insufficient. In such case binary file is used.
Working of binary files is similar to text files with few differences in opening modes, reading from file and writing to file.
Opening modes of binary files
Opening modes of binary files are rb, rb+, wb, wb+,ab and ab+. The only difference between opening modes of text and binary files is that, b is appended to indicate that, it is binary file.
Reading and writing of a binary file.
Functions fread() and fwrite() are used for reading from and writing to a file on the disk respectively in case of binary files.
Function fwrite() takes four arguments, address of data to be written in disk, size of data to be written in disk, number of such type of data and pointer to the file where you want to write.
fwrite(address_data,size_data,numbers_data,pointer_to_file);
Function fread() also take 4 arguments similar to fwrite() function as above.
File Examples
Examples Of Files In C Programming
C Program to read name and marks of students and store it in file
C Program to read name and marks of students and store it in file. If file already exists,
add information to it.
Examples Of Files In C Programming
C Program to write members of arrays to a file using fwrite()
Write a C program to read name and marks of n number of students from user and store them in a file
#include <stdio.h>
int main(){
char name[50];
int marks,i,n;
printf("Enter number of students: ");
scanf("%d",&n);
FILE *fptr;
fptr=(fopen("C:\\student.txt","w"));
if(fptr==NULL){
printf("Error!");
exit(1);
}
for(i=0;i<n;++i)
{
printf("For student%d\nEnter name: ",i+1);
scanf("%s",name);
printf("Enter marks: ");
scanf("%d",&marks);
fprintf(fptr,"\nName: %s \nMarks=%d \n",name,marks);
}
fclose(fptr);
return 0;
}
Write a C program to read name and marks of n number of students from user and store them in a file. If the file
previously exits, add the information of n students.
#include <stdio.h>
int main(){
char name[50];
int marks,i,n;
printf("Enter number of students: ");
scanf("%d",&n);
FILE *fptr;
fptr=(fopen("C:\\student.txt","a"));
if(fptr==NULL){
printf("Error!");
exit(1);
}
for(i=0;i<n;++i)
{
printf("For student%d\nEnter name: ",i+1);
scanf("%s",name);
printf("Enter marks: ");
scanf("%d",&marks);
fprintf(fptr,"\nName: %s \nMarks=%d \n",name,marks);
}
fclose(fptr);
return 0;
}
Write a C program to write all the members of an array of strcures to a file using fwrite(). Read the array from the file and display on the screen.
#include <stdio.h>