fseek : <stdio.h> library function

The function int fseek(FILE *stream, long int offset, int where); sets the position indicator of the stream to a new position. The new position is defined by adding offset to a reference position specified by where. The value of where should be one of the following constants defined in stdio.h header file.

Constant Description
SEEK_SET Beginning of file
SEEK_END End of file
SEEK_CUR Current position of the file pointer

Function prototype of fseek

int fseek(FILE *stream, long int offset, int where);
  • stream : This is a pointer to a FILE object which identifies a stream.
  • offset : This is the number of bytes to offset from where.
  • where : This is the position from where offset is added to set new position of file position indicator.

Return value of fseek

This function returns a zero on success otherwise it returns a non-zero value.

C program to show the use of fseek function

The following program shows the use of fseek function to set the file position indicator to 4th position instead of starting from 0th position.

#include 

int main(){
   FILE *file;
   int ch;
   
   /* Open a file for reading */
   file = fopen("textFile.txt","w+");
   if(file == NULL){
      perror("Error: Unable to open a file");
      return(1);
   } else {
       fputs("TechCrashCourse.com", file);
       /*Setting file pointer position to 5th Character */
       fseek(file, 4, SEEK_SET);
       /* It will skip first four characters */
       while(!feof(file)){
          ch = fgetc(file);
          printf("%c", ch);
       }
       fclose(file);
   }
   
   return(0);
}

Program Output
CrashCourse.com