adjtimex - phpMan

ADJTIMEX(2)                Linux Programmer’s Manual               ADJTIMEX(2)



NAME
       adjtimex - tune kernel clock

SYNOPSIS
       #include <sys/timex.h>

       int adjtimex(struct timex *buf);

DESCRIPTION
       Linux  uses  David L. Mills’ clock adjustment algorithm (see RFC 1305).  The system
       call adjtimex reads and optionally sets adjustment parameters for  this  algorithm.
       It  takes a pointer to a timex structure, updates kernel parameters from field val-
       ues, and returns the same structure with current kernel values.  This structure  is
       declared as follows:

              struct timex {
                  int modes;           /* mode selector */
                  long offset;         /* time offset (usec) */
                  long freq;           /* frequency offset (scaled ppm) */
                  long maxerror;       /* maximum error (usec) */
                  long esterror;       /* estimated error (usec) */
                  int status;          /* clock command/status */
                  long constant;       /* pll time constant */
                  long precision;      /* clock precision (usec) (read only) */
                  long tolerance;      /* clock frequency tolerance (ppm)
                                          (read only) */
                  struct timeval time; /* current time (read only) */
                  long tick;           /* usecs between clock ticks */
              };

       The modes field determines which parameters, if any, to set.  It may contain a bit-
       wise-or combination of zero or more of the following bits:

              #define ADJ_OFFSET            0x0001 /* time offset */
              #define ADJ_FREQUENCY         0x0002 /* frequency offset */
              #define ADJ_MAXERROR          0x0004 /* maximum time error */
              #define ADJ_ESTERROR          0x0008 /* estimated time error */
              #define ADJ_STATUS            0x0010 /* clock status */
              #define ADJ_TIMECONST         0x0020 /* pll time constant */
              #define ADJ_TICK              0x4000 /* tick value */
              #define ADJ_OFFSET_SINGLESHOT 0x8001 /* old-fashioned adjtime */

       Ordinary users are restricted to a zero value for mode.  Only the superuser may set
       any parameters.

RETURN VALUE
       On success, adjtimex returns the clock state:

              #define TIME_OK   0 /* clock synchronized */
              #define TIME_INS  1 /* insert leap second */
              #define TIME_DEL  2 /* delete leap second */
              #define TIME_OOP  3 /* leap second in progress */
              #define TIME_WAIT 4 /* leap second has occurred */
              #define TIME_BAD  5 /* clock not synchronized */

       On failure, adjtimex returns -1 and sets errno.

ERRORS
       EFAULT buf does not point to writable memory.

       EPERM  buf.mode is non-zero and the user is not super-user.

       EINVAL An attempt is made to set buf.offset to a value outside the range -131071 to
              +131071, or to set buf.status to a value other than those listed  above,  or
              to  set buf.tick to a value outside the range 900000/HZ to 1100000/HZ, where
              HZ is the system timer interrupt frequency.

CONFORMING TO
       adjtimex is Linux specific and should not  be  used  in  programs  intended  to  be
       portable.  There is a similar but less general call adjtime in SVr4.

SEE ALSO
       settimeofday(2)



Linux 2.0                         1997-07-30                       ADJTIMEX(2)

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