zkFcntl.h is a portable wrapper for the Unix 98 header <fcntl.h>. It is part of the libzk library because <sys/stat.h> doesn't exist in Standard C.

zkFcntl.h - Supported Macros from <fcntl.h>
Macro Description
F_GETFL Get file status flags and file access modes.
F_SETLK Set record locking information.
F_UNLCK Unlock.
F_WRLCK Exclusive or write lock.
O_ACCMODE Mask for file access modes
O_RDONLY Open for reading only.
O_RDWR Open for reading and writing.
O_WRONLY Open for writing only.
O_APPEND Set append mode.
O_CREAT Create file if it does not exist.
O_EXCL Exclusive use flag.
O_TRUNC Truncate flag.

zkFcntl.h - Supported Types from <fcntl.h>
Type Description
struct flock, with members:  
short l_type
type of lock; F_RDLCK, F_WRLCK, F_UNLCK
short l_whence
flag for starting offset
off_t l_start
relative offset in bytes
off_t l_len
size; if 0 then until EOF

zkFcntl.h - Deprecated Functions from <fcntl.h>
Don't Call This Instead, Call This Reason
creat zkCreat Not in Standard C.
fcntl zkFcntl Not in Standard C.
open zkOpen Not in Standard C.