Linux Standard Base Core Specification 2.0.1
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adjtimex

Name

adjtimex -- tune kernel clock (DEPRECATED)

Synopsis

#include <sys/timex.h>

int adjtimex((struct timex *buf));

Description

The adjtimex function is deprecated from the LSB and is expected to disappear from a future version of the LSB.

Note

The LSB generally does not include interfaces unlikely to be used by software applications.

Linux uses David L. Mills' clock adjustment algorithm (see RFC 1305). adjtimex reads and optionally sets adjustment parameters for this algorithm. adjtimex takes a pointer to a timex structure, updates kernel parameters from field values, 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 */
  };

modes determines which parameters, if any, to set. modes may contain a bitwise-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 0 value for modes. 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 error, the global variable errno is set to -1.

Errors

EFAULT

buf does not point to writable memory.

EPERM

buf.mode is nonzero and the user is not super-user.

EINVAL

An attempt is made to set buf.offset to a value outside of 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 of the range 900000/HZ to 1100000/HZ, where HZ is the system timer interrupt frequency.

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