Searching and Sparse Files

#include<stdio.h>
FILE *fopen(const char *pathname, const char *mode);
size_t fread(void *ptr, size_t size, size_t nmemb, FOLE *stream);
int fseek(FILE *stream. long offset, int whence);
int fclose(FILE *stream);

• The behavior of fseek() depends on the argument: SEEK_CUR, SEEK_END, or SEEK_SET.

• The method returns the new file position on success.

• On error, it returns -1, and error information is written to errno.

• Seeking past the end of a file and then writing to it causes holes filled with zeros.

• Files with holes are called sparse files.

• Holes do not occupy physical disk space.

• du = estimate of the disk space used by the file.

Argument	Description
SEEK_CUR	Takes the value of the current file position (fd) plus the value POS, which can be negative, zero, or positive. POS of zero returns the value of the current file position.
SEEK_END	The value of the current file position (fd) becomes equal to the file length plus the value POS, which can be negative, zero, or positive. POS of zero sets the offset to the end of the file.
SEEK_SET	The value of the current file position (fd) becomes equal to the value POS. POS of zero sets the offset to the beginning of the file.

More information: Sparse Files