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 .