C Programming Tutorial
The fseek() function is used to set the file pointer to the specified offset. It is used to write data into file at desired location.
Syntax:
int fseek(FILE *stream, long int offset, int whence)
There are 3 constants used in the fseek() function for whence: SEEK_SET, SEEK_CUR and SEEK_END.
Example:
#include <stdio.h>
void main(){
FILE *fp;
fp = fopen("myfile.txt","w+");
fputs("This is javatpoint", fp);
fseek( fp, 7, SEEK_SET );
fputs("Rama", fp);
fclose(fp);
}
newfile.txt
This is Rama
EXAMPLE PROGRAM FOR FSEEK(), SEEK_SET(), SEEK_CUR(), SEEK_END() FUNCTIONS IN C:
#include <stdio.h>
int main ()
{
FILE *fp;
char data[60];
fp = fopen ("test.c","w");
fputs("Fresh2refresh.com is a programming tutorial website", fp);
fgets ( data, 60, fp );
printf(Before fseek - %s", data);
// To set file pointet to 21th byte/character in the file
fseek(fp, 21, SEEK_SET);
fflush(data);
fgets ( data, 60, fp );
printf("After SEEK_SET to 21 - %s", data);
// To find backward 10 bytes from current position
fseek(fp, -10, SEEK_CUR);
fflush(data);
fgets ( data, 60, fp );
printf("After SEEK_CUR to -10 - %s", data);
// To find 7th byte before the end of file
fseek(fp, -7, SEEK_END);
fflush(data);
fgets ( data, 60, fp );
printf("After SEEK_END to -7 - %s", data);
// To set file pointer to the beginning of the file
fseek(fp, 0, SEEK_SET); // We can use rewind(fp); also
fclose(fp);
return 0;
}
OUTPUT:
Before fseek – Fresh2refresh.com is a programming tutorial website
After SEEK_SET to 21 – a programming tutorial website
After SEEK_CUR to -10 – sh.com is a programming tutorial website
After SEEK_END to -7 – website
