Is there File Share Mode in Linux

[nabilchampion]

Hi all
I have a situation where I have a function written in Windows and need to be ported on Linux.

function has prototype something like this

ERROR open_file(char *filename,..., MODE mode, SHARE_MODE sh_mode)

in the function body the function calls windows API function CreateFile()
to open the file. CreateFile() also takes a parameter for Share Mode. The effect of share mode is that if we provide 0 value for this argument then while the file handle is open no other process can read or write to this file.
here is the prototype for CreateFile()

HANDLE CreateFile(
  LPCTSTR lpFileName,
  DWORD dwDesiredAccess,
  DWORD dwShareMode,
  LPSECURITY_ATTRIBUTES lpSecurityAttributes,
  DWORD dwCreationDisposition,
  DWORD dwFlagsAndAttributes,
  HANDLE hTemplateFile
);

My problem is that while I can have found almost all flags for mode and other in Linux open() system call but I found no match for this Share Mode alternative. While my file descriptor is still open other process can access the file and change its contents. Please some one guide me that what is the best possible alternative in Linux to provide complete functionality of this Share Mode option. Windows provides 3 flags FILE_SHARE_CREATE, FILE_SHARE_READ, FILE_SHARE_DELETE and zero(0)

[gjpc]

All files in *nix are assumed shared. There are are file locking primitives see: fcntl(3): file control - Linux man page