lseek (2) Linux Manual Page

NAME

lseek – reposition read/write file offset

SYNOPSIS

#include <sys/types.h>
#include <unistd.h>

off_t lseek(int fd, off_t offset, int whence);

DESCRIPTION

lseek() repositions the file offset of the open file description associated with the file descriptor fd to the argument offset according to the directive whence as follows:

SEEK_SET

The file offset is set to offset bytes.

SEEK_CUR

The file offset is set to its current location plus offset bytes.

SEEK_END

The file offset is set to the size of the file plus offset bytes.

lseek() allows the file offset to be set beyond the end of the file (but this does not change the size of the file). If data is later written at this point, subsequent reads of the data in the gap (a "hole") return null bytes (‘