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):
                 F_DUPFD        Duplicate file descriptor
                 F_GETFD        Get file descriptor flags
                 F_SETFD        Set file descriptor flags
                 F_GETFL        Get file status flags
                 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_CHKFL        Unused
                 F_ALLOCSP      Reserved
                 F_FREESP       Free file space
                 F_ISSTREAM     Is the file desc. a stream
                 F_BLOCKS       Get number of BLKSIZE
                                blocks allocated
                 F_BLKSIZE      Get optimal I/O block size

                 F_RSETLK       Remote SETLK for NFS
                 F_RGETLK       Remote GETLK for NFS
                 F_RSETLKW      Remote SETLKW for NFS

                 F_GETOWN       Get owner (socket emulation)
                 F_SETOWN       Set owner (socket emulation)
            File descriptor flags used for fcntl:

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

            Values for l_type used for record locking with fcntl
            (the following values are unique):
                 F_RDLCK        Shared or read lock
                 F_UNLCK        Unlock
                 F_WRLCK        Exclusive or write lock

            The following three sets of values are bitwise distinct:
            Values for oflag used by open:
                 O_CREAT        Create file if it does not exist
                 O_EXCL         Exclusive use flag
                 O_NOCTTY       Do not assign controlling tty
                 O_TRUNC        Truncate flag


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   fcntl(5)                                                           fcntl(5)



            File status flags used for open and fcntl:
                 O_APPEND       Set append mode
                 O_NDELAY       Non-blocking mode
                 O_NONBLOCK     Non-blocking mode (POSIX)
                 O_SYNC         Synchronous writes
                 O_PRIV         Private access to file

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

            File access modes used for open and fcntl:
                 O_RDONLY       Open for reading only
                 O_RDWR         Open for reading and writing
                 O_WRONLY       Open for writing only

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

            short   l_type;     /* Type of lock */
            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;      /* Returned with F_GETLK */
            short    l_sysid;    /* Returned with F_GETLK */

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

























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