What do these system calls do?

[mrsmkl]

14. mknod . what is this?
15. Access: what is this?
16. Ioctl
17. umask
18. Readlink: ???
19. Msync: ???
20. Fcntl64
21. Mknodat
22. Faccessat
23. Fallocate

[terminaldweller]

mknod : creates a file system node (file, device special file or named pipe)
access : checks the access rights of the calling pid to a directory provided
ioctl : changes the parameters of a device drive through accessing the device file
umask : sets the file creation mask (for example when you fork a child process you use this to manipulate the child process' access rights)
readlink : print the value of a symlink
msync : flushes changes to a file. its mostly there to ensure file intergrity in case something goes bad during making changes to the memory-mapped copy of a file since munmap will unmap the file regardless.
fcntl64 ; performs operations on the fd based on the "cmd" arg passed to it
mknodat : does the same as mknod plus takes an extra arg that open the fs node relative to that arg instead of CWD
faccessat : the same as access plus an extra arg. the path arg will ne relative to this extra arg instead of CWD
fallocate : either deallocate or preallocate disk space to a file on filesystems that support it