fcntl(M)                        19 June 1992                        fcntl(M)


 Name

    fcntl - file control options

 Syntax

    #include <fcntl.h>

 Description

    The fcntl(S) function provides for control over open files.  This include
    file describes requests and arguments to fcntl and open(S).

    /* Flag values accessible to open(S) and fcntl(S) */
    /*  (The first three can only be set by open) */
    #define  O_RDONLY   0
    #define  O_WRONLY   1
    #define  O_RDWR     2
    #define  O_NDELAY   04       /* Non-blocking I/O */
    #define  O_APPEND   010      /* append (writes guaranteed at the end) */
    #define  O_SYNC     020      /* synchronous write option */

    /* Flag values accessible only to open(S) */
    #define  O_CREAT    00400    /* open with file create (uses third open arg)*/
    #define  O_TRUNC    01000    /* open with truncation */
    #define  O_EXCL     02000    /* exclusive open */

    /* fcntl(S) requests */
    #define  F_DUPFD    0        /* Duplicate fildes */
    #define  F_GETFD    1        /* Get fildes flags */
    #define  F_SETFD    2        /* Set fildes flags */
    #define  F_GETFL    3        /* Get file flags */
    #define  F_SETFL    4        /* Set file flags */
    #define  F_GETLK    5        /* Get file lock */
    #define  F_SETLK    6        /* Set file lock */
    #define  F_SETLKW   7        /* Set file lock and wait */
    #define  F_CHKFL    8        /* Check legality of file flag changes */

    /* file segment locking control structure */
    struct flock {
             short   l_type;
             short   l_whence;
             long    l_start;
             long    l_len;      /* if 0 then until EOF */
             short   l_sysid;    /* returned with F_GETLK*/
             short   l_pid;      /* returned with F_GETLK*/
    }

    /* file segment locking types */
    #define  F_RDLCK    01       /* Read lock */
    #define  F_WRLCK    02       /* Write lock */
    #define  F_UNLCK    03       /* Remove locks */

 See also

    fcntl(S), open(S)

 Standards conformance

    fcntl is conformant with:

    AT&T SVID Issue 2;
    and X/Open Portability Guide, Issue 3, 1989.