OPEN(2) 							System Calls Manual							   OPEN(2)

NAME

       open, create, close - open a file for reading or writing, create file

SYNOPSIS

       #include <u.h>
       #include <libc.h>

       int open(char *file, int omode)

       int create(char *file, int omode, ulong perm)

       int close(int fd)

DESCRIPTION

       Open  opens the file for I/O and returns an associated file descriptor.	Omode is one of OREAD, OWRITE, ORDWR, or OEXEC, asking for permis-
       sion to read, write, read and write, or execute, respectively.  In addition, there are three values that can be ORed with the omode: OTRUNC
       says to truncate the file to zero length before opening it; OCEXEC says to close the file when an exec(2) or execl system call is made; and
       ORCLOSE says to remove the file when it is closed (by everyone who has a copy of the file descriptor).  Open fails if  the  file  does  not
       exist  or  the user does not have permission to open it for the requested purpose (see stat(2) for a description of permissions).  The user
       must have write permission on the file if the OTRUNC bit is set.  For the open system call (unlike the implicit open in exec(2)), OEXEC	is
       actually identical to OREAD.

       Create  creates	a  new	file  or prepares to rewrite an existing file, opens it according to omode (as described for open), and returns an
       associated file descriptor.  If the file is new, the owner is set to the userid of the creating process group; the group  to  that  of  the
       containing  directory;  the  permissions to perm ANDed with the permissions of the containing directory.  If the file already exists, it is
       truncated to 0 length, and the permissions, owner, and group remain unchanged.  The created file is a directory if the CHDIR bit is set	in
       omode.	It  is	an exclusive-use file if the CHEXCL bit is set.  Such files may be open for I/O by only one client at a time, but the file
       descriptor may become invalid if no I/O is done for an extended period; see open(5).

       Create fails if the path up to the last element of file cannot be evaluated, if the user doesn't have write permission in the final  direc-
       tory,  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 intro(2)) then the constituent directory where the file is created depends on the structure of the union:
       see bind(2).

       Close  closes  the file associated with a file descriptor.  Provided the file descriptor is a valid open descriptor, close is guaranteed to
       close it; there will be no error.  Files are closed automatically upon termination of a process; close allows the  file	descriptor  to	be
       reused.

SOURCE

       /sys/src/libc/9syscall

SEE ALSO

       intro(2), bind(2), stat(2)

DIAGNOSTICS

       These functions set errstr.

																	   OPEN(2)