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<fcntl.h>(P)		   POSIX Programmer's Manual		  <fcntl.h>(P)

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the	 corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.

NAME
       fcntl.h - file control options

SYNOPSIS
       #include <fcntl.h>

DESCRIPTION
       The <fcntl.h> header shall define the following requests and  arguments
       for use by the functions fcntl() and open().

       Values for cmd used by fcntl() (the following values are unique) are as
       follows:

       F_DUPFD
	      Duplicate file descriptor.

       F_GETFD
	      Get file descriptor flags.

       F_SETFD
	      Set file descriptor flags.

       F_GETFL
	      Get file status flags and file access modes.

       F_SETFL
	      Set file status flags.

       F_GETLK
	      Get record locking information.

       F_SETLK
	      Set record locking information.

       F_SETLKW
	      Set record locking information; wait if blocked.

       F_GETOWN
	      Get process or process group ID to receive SIGURG signals.

       F_SETOWN
	      Set process or process group ID to receive SIGURG signals.

       File descriptor flags used for fcntl() are as follows:

       FD_CLOEXEC
	      Close the file descriptor upon execution of an exec family func‐
	      tion.

       Values  for  l_type used for record locking with fcntl() (the following
       values are unique) are as follows:

       F_RDLCK
	      Shared or read lock.

       F_UNLCK
	      Unlock.

       F_WRLCK
	      Exclusive or write lock.

       The values used for l_whence, SEEK_SET, SEEK_CUR, and SEEK_END shall be
       defined as described in <unistd.h> .

       The  following values are file creation flags and are used in the oflag
       value to open(). They shall be bitwise-distinct.

       O_CREAT
	      Create file if it does not exist.

       O_EXCL Exclusive use flag.

       O_NOCTTY
	      Do not assign controlling terminal.

       O_TRUNC
	      Truncate flag.

       File status flags used for open() and fcntl() are as follows:

       O_APPEND
	      Set append mode.

       O_DSYNC
	      Write according to synchronized I/O data integrity completion.

       O_NONBLOCK
	      Non-blocking mode.

       O_RSYNC
	      Synchronized read I/O operations.

       O_SYNC Write according to synchronized I/O file integrity completion.

       Mask for use with file access modes is as follows:

       O_ACCMODE
	      Mask for file access modes.

       File access modes used for open() and fcntl() are as follows:

       O_RDONLY
	      Open for reading only.

       O_RDWR Open for reading and writing.

       O_WRONLY
	      Open for writing only.

       The symbolic names for file modes for use as values of mode_t shall  be
       defined as described in <sys/stat.h> .

       Values for advice used by posix_fadvise() are as follows:

       POSIX_FADV_NORMAL

	      The  application	has  no	 advice	 to  give on its behavior with
	      respect to the specified data. It is the default	characteristic
	      if no advice is given for an open file.

       POSIX_FADV_SEQUENTIAL

	      The  application	expects	 to  access the specified data sequen‐
	      tially from lower offsets to higher offsets.

       POSIX_FADV_RANDOM

	      The application expects to access the specified data in a random
	      order.

       POSIX_FADV_WILLNEED

	      The application expects to access the specified data in the near
	      future.

       POSIX_FADV_DONTNEED

	      The application expects that it will not	access	the  specified
	      data in the near future.

       POSIX_FADV_NOREUSE

	      The  application	expects	 to access the specified data once and
	      then not reuse it thereafter.

       The structure flock describes a file lock. It shall include the follow‐
       ing members:

	      short  l_type   Type of lock; F_RDLCK, F_WRLCK, F_UNLCK.
	      short  l_whence Flag for starting offset.
	      off_t  l_start  Relative offset in bytes.
	      off_t  l_len    Size; if 0 then until EOF.
	      pid_t  l_pid    Process ID of the process holding the lock; returned with F_GETLK.

       The  mode_t,  off_t,  and  pid_t types shall be defined as described in
       <sys/types.h> .

       The following shall be declared as functions and may also be defined as
       macros. Function prototypes shall be provided.

	      int  creat(const char *, mode_t);
	      int  fcntl(int, int, ...);
	      int  open(const char *, int, ...);

	      int  posix_fadvise(int, off_t, size_t, int);
	      int  posix_fallocate(int, off_t, size_t);

       Inclusion  of  the  <fcntl.h>  header may also make visible all symbols
       from <sys/stat.h> and <unistd.h>.

       The following sections are informative.

APPLICATION USAGE
       None.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       <sys/stat.h> , <sys/types.h> , <unistd.h> , the System Interfaces  vol‐
       ume of IEEE Std 1003.1-2001, creat(), exec, fcntl(), open(), posix_fad‐
       vise(), posix_fallocate(), posix_madvise()

COPYRIGHT
       Portions of this text are reprinted and reproduced in  electronic  form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX),	The  Open  Group  Base
       Specifications  Issue  6,  Copyright  (C) 2001-2003 by the Institute of
       Electrical and Electronics Engineers, Inc and The Open  Group.  In  the
       event of any discrepancy between this version and the original IEEE and
       The Open Group Standard, the original IEEE and The Open Group  Standard
       is  the	referee document. The original Standard can be obtained online
       at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group		     2003			  <fcntl.h>(P)
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