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AIX Version 4 Files Reference
fcntl.h File
Purpose
Defines file control options.
Description
The /usr/include/fcntl.h file defines the values that can be specified for the Command and Argument parameters of the fcntl subroutine and for the Oflag parameter of the open subroutine. The file-status flags of an open file are described in the following information.
Flag Values for open Subroutine
The following flag values are accessible only to the open subroutine:
O_RDONLY |
Read-only |
O_WRONLY |
Write-only |
O_RDWR |
Read and write |
O_CREAT |
Open with file create (uses the third open argument) |
O_TRUNC |
Open with truncation |
O_DIRECT |
Open for Direct I/O |
O_EXCL |
Exclusive open
Note: The O_EXCL flag is not fully supported for Network File Systems (NFS). The NFS protocol does not guarantee the designed function of the O_EXCL flag.
|
O_NOCTTY |
Do not assign a controlling terminal |
O_RSHARE |
Read shared open |
O_NSHARE |
Read shared open |
File Access Mode Mask
The O_ACCMODE mask is used to determine the file access mode.
File Status flags for open and fcntl Subroutines
The following file status flags are accessible to both the open and fcntl subroutines:
O_NONBLOCK |
POSIX nonblocking I/O |
FNONBLOCK |
POSIX nonblocking I/O |
O_APPEND |
An append with writes guaranteed at the end |
FAPPEND |
An append with writes guaranteed at the end |
O_SYNC |
Synchronous write option |
FSYNC |
Synchronous write option |
O_DSYNC |
Synchronous write option (file data only). |
FDATASYNC |
Synchronous write option (file data only). |
O_RSYNC |
Synchronous file attributes on read. |
FREADSYNC |
Synchronous file attributes on read. |
FASYNC |
Asynchronous I/O |
O_NDELAY |
Nonblocking I/O |
FNDELAY |
Nonblocking I/O |
O_LARGEFILE |
Access to large files enabled
(AIX versions 4.2 and later) |
File Status Flags for open Subroutine
The following file status flags are accessible to the open subroutine:
O_DEFER |
Deferred update |
O_DELAY |
Open with delay |
O_DIRECT |
Open for Direct I/O |
File Descriptor Flags for fcntl Subroutine
The following file descriptor flag is accessible to the fcntl subroutine:
FD_CLOEXEC |
Close this file during an exec. |
File flag values corresponding to file access modes are as follows:
FREAD |
File is open for read. |
FWRITE |
File is open for write. |
Notes:
- The FREAD and FWRITE flags cannot be used unless the _KERNEL flag has been defined.
- The ldfcn.h file also assigns values to the FREAD and FWRITE options. If you use the ldfcn.h and fcntl.h files together, directly or indirectly, you should use the #undef statement on the FREAD and FWRITE options of one of the header files. If you do not, the compiler will return a warning about using duplicate definitions.
Command Values for fcntl Subroutine
The Command values for the fcntl subroutine (that is, for fcntl subroutine requests) are:
F_DUPFD |
Duplicate the file description. |
F_GETFD |
Get the file description flags. |
F_SETFD |
Set the file description flags. |
F_GETFL |
Get the file status flags and file access modes. |
F_SETFL |
Set the file flags. |
F_GETLK |
Return information about an existing file lock. |
F_GETLK64 |
Return information about an existing file lock
(AIX versions 4.2 and later)
. |
F_SETLK |
Set or clear a file lock. |
F_SETLK64 |
Set or clear a file lock
(AIX versions 4.2 and later)
. |
F_SETLKW |
Set or clear a file lock and wait if blocked. |
F_SETLKW64 |
Set or clear a file lock and wait if blocked
(AIX versions 4.2 and later)
. |
F_GETOWN |
Get the descriptor owner. |
F_SETOWN |
Set the descriptor owner. |
Related Information
The fcntl subroutine,
open, openx, or creat subroutine.
The sys/types.h file,
unistd.h file.
The Header Files Overview defines header files, describes how they are used, and lists several header files for which information is provided.
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