File is collection of records or is a place on hard disk, where data is stored permanently.
Operations on files
The operations on files in C programming 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 a file is as follows −
FILE *File pointer;
For example, FILE * fptr;
The syntax for naming a file is as follows −
File pointer = fopen ("File name", "mode");For example,
fptr = fopen ("sample.txt", "r");
FILE *fp;
fp = fopen ("sample.txt", "w");putw( ) and getw( ) functions
putw( ) function is used for writing a number into file.
The syntax for putw() function is as follows −
Syntax
putw (int num, FILE *fp);
For example,
Example
FILE *fp; int num; putw(num, fp);
getw( ) function is used for reading a number from a file.
The syntax for getw() function is as follows −
Syntax
int getw (FILE *fp);
For example,
Example
FILE *fp; int num; num = getw(fp);
The logic for writing numbers into a file is as follows −
fp = fopen ("num.txt", "w");
for (i =1; i<= 10; i++){
putw (i, fp);
}
fclose (fp);The logic for reading numbers from a file is as follows −
fp =fopen ("num.txt", "r");
printf ("file content is\n");
for (i =1; i<= 10; i++){
i= getw(fp);
printf ("%d",i);
printf("\n");
}
fclose (fp);Program
Following is the C program for storing the numbers from 1 to 10 and to print the same −
#include<stdio.h>
int main( ){
FILE *fp;
int i;
fp = fopen ("num.txt", "w");
for (i =1; i<= 10; i++){
putw (i, fp);
}
fclose (fp);
fp =fopen ("num.txt", "r");
printf ("file content is\n");
for (i =1; i<= 10; i++){
i= getw(fp);
printf ("%d",i);
printf("\n");
}
fclose (fp);
return 0;
}Output
When the above program is executed, it produces the following result −
file content is 1 2 3 4 5 6 7 8 9 10