有些书上叫记录锁:
int fcntl(int filedes,int cmd,struct flock *flockptr);
cmd:F_GETLK,F_SETLK,F_SETLKW
struct flock {
short l_type;//F_RDLCK,F_WRLCK,or F_UNLCK
off_t l_start;//offset in bytes,relative to l_whence
short l_whence;//SEEK_SET,SEEK_CUR,or SEEK_END
off_t l_len;//length,in bytes;0 means lock to EOF
pid_t l_pid;//returned with F_GETLK
};