linux open lseek

#include <sys/types.h>#include <unistd.h>#include <sys/stat.h>#include <fcntl.h>#include <stdio.h>int main(){struct timeval{unsigned int tv_sec;unsigned int tv_usec;};struct timeval time_a;int fd = open("timefile", O_RDONLY);lseek( fd, 4, SEEK_SET );read( fd, &(time_a.tv_usec),4 );        close( fd );printf("time  = %d.%d\n", time_a.tv_sec, time_a.tv_usec  );return 0;}

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

SEEK_SET
              The offset is set to offset bytes.

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

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

man 2 lseek