include "sys.m";
sys:= load Sys Sys->PATH;
open:  fn(file: string, omode: int)      : ref FD;
create:fn(file: string, omode, perm: int): ref FD;

The following values may be OR'ed with the above values for additional actions:

OTRUNC	Truncate the file before opening it; this requires write permission even if omode is OREAD.
ORCLOSE	Remove the file on closure.

The open function returns nil if the file does not exist or the user does not have permission to open it as requested (see stat, fstat, fwstat, wstat - get and put file status for a description of permissions).

create (file, omode, perm)

If the file is new, the owner is set to the user id of the creating process group, the group to that of the containing directory. Also the permissions to perm are AND'ed with the permissions of the containing directory. See the section - The create Transaction in Chapter 3 of open.

If the file already exists, it is truncated to 0 length, and the permissions, owner, and group remain unchanged.

file mode bits in perm

16r80000000	Directory. The Sys module defines this as CHDIR.
8r400	Read permission by owner.
8r200	Write permission by owner.
8r100	Execute permission (search on directory) by owner
8r070	Read, write, execute (search) by group.
8r007	Read, write, execute (search) by others.

The create function returns nil if the path up to the last element of file cannot be evaluated, if the user does not have write permission in the final directory, or if the file already exists and does not permit the access defined by omode.

If the file is new and the directory in which it is created is a union directory (see Limbo System Module), then the directory where the file is created depends on the structure of the union: see bind, mount, unmount - change file name space.

Caveat

For devices and network protocols where shutdown must be guaranteed, write a hangup message to the associated control file and use the return value of the write to verify closure. For example, see ip - TCP, UDP network protocols over IP in Chapter 2.

See Also

Limbo System Module

bind, mount, unmount - change file name space

stat, fstat, fwstat, wstat - get and put file status

open, create - prepare a fid for I/O on a file in Chapter 3