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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
              function.

       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
              sequentially 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
       following 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
       volume  of  IEEE Std 1003.1-2001,  creat(),  exec,   fcntl(),   open(),
       posix_fadvise(), 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 .