fcntl(5)                                                           fcntl(5)


   NAME
         fcntl - file control options

   SYNOPSIS
         #include <fcntl.h>

   DESCRIPTION
         The <fcntl.h> header defines the following requests and arguments for
         use by the functions fcntl [see fcntl(2)] and open [see open(2)].

            Values for cmd used by fcntl (the following values are unique):
                 FDUPFD        Duplicate file descriptor
                 FGETFD        Get file descriptor flags
                 FSETFD        Set file descriptor flags
                 FGETFL        Get file status flags
                 FSETFL        Set file status flags
                 FGETLK        Get record locking information
                 FSETLK        Set record locking information
                 FSETLKW       Set record locking information;
                                wait if blocked
                 FCHKFL        Unused
                 FALLOCSP      Reserved
                 FFREESP       Free file space
                 FISSTREAM     Is the file desc. a stream
                 FBLOCKS       Get number of BLKSIZE
                                blocks allocated
                 FBLKSIZE      Get optimal I/O block size

                 FRSETLK       Remote SETLK for NFS
                 FRGETLK       Remote GETLK for NFS
                 FRSETLKW      Remote SETLKW for NFS

                 FGETOWN       Get owner (socket emulation)
                 FSETOWN       Set owner (socket emulation)
            File descriptor flags used for fcntl:

                 FDCLOEXEC     Close the file descriptor upon
                                execution of an exec function [see exec(2)]

            Values for ltype used for record locking with fcntl
            (the following values are unique):
                 FRDLCK        Shared or read lock
                 FUNLCK        Unlock
                 FWRLCK        Exclusive or write lock

            The following three sets of values are bitwise distinct:
            Values for oflag used by open:
                 OCREAT        Create file if it does not exist
                 OEXCL         Exclusive use flag
                 ONOCTTY       Do not assign controlling tty
                 OTRUNC        Truncate flag


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   fcntl(5)                                                           fcntl(5)



            File status flags used for open and fcntl:
                 OAPPEND       Set append mode
                 ONDELAY       Non-blocking mode
                 ONONBLOCK     Non-blocking mode (POSIX)
                 OSYNC         Synchronous writes
                 OPRIV         Private access to file

            Mask for use with file access modes:
                 OACCMODE      Mask for file access modes

            File access modes used for open and fcntl:
                 ORDONLY       Open for reading only
                 ORDWR         Open for reading and writing
                 OWRONLY       Open for writing only

         The structure flock describes a file lock.  It includes the following
         members:

            short   ltype;     /* Type of lock */
            short   lwhence;   /* Flag for starting offset */
            offt   lstart;    /* Relative offset in bytes */
            offt   llen;      /* Size; if 0 then until EOF */
            pidt   lpid;      /* Returned with FGETLK */
            short    lsysid;    /* Returned with FGETLK */

   SEE ALSO
         creat(2), exec(2), fcntl(2), open(2).

























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