FreeBSD 7.0 manual page repository

FreeBSD is a free computer operating system based on BSD UNIX originally. Many IT companies, like DeployIS is using it to provide an up-to-date, stable operating system.

clock_gettime, clock_settime, clock_getres - get/set/calibrate date and

 

NAME

      clock_gettime, clock_settime, clock_getres - get/set/calibrate date and
      time
 

LIBRARY

      Standard C Library (libc, -lc)
 

SYNOPSIS

      #include <time.h>
 
      int
      clock_gettime(clockid_t clock_id, struct timespec *tp);
 
      int
      clock_settime(clockid_t clock_id, const struct timespec *tp);
 
      int
      clock_getres(clockid_t clock_id, struct timespec *tp);
 

DESCRIPTION

      The clock_gettime() and clock_settime() allow the calling process to
      retrieve or set the value used by a clock which is specified by clock_id.
 
      The clock_id argument can be one of five values: CLOCK_REALTIME for time
      that increments as a wall clock should, CLOCK_MONOTONIC which increments
      in SI seconds, CLOCK_UPTIME which starts at zero when the kernel boots
      and increments monotonically in SI seconds while the machine is running,
      CLOCK_VIRTUAL for time that increments only when the CPU is running in
      user mode on behalf of the calling process, or CLOCK_PROF for time that
      increments when the CPU is running in user or kernel mode.
 
      The structure pointed to by tp is defined in #include <sys/timespec.h>
      as:
 
      struct timespec {
              time_t  tv_sec;         /* seconds */
              long    tv_nsec;        /* and nanoseconds */
      };
 
      Only the super-user may set the time of day.  If the system securelevel
      is greater than 1 (see init(8)), the time may only be advanced.  This
      limitation is imposed to prevent a malicious super-user from setting
      arbitrary time stamps on files.  The system time can still be adjusted
      backwards using the adjtime(2) system call even when the system is
      secure.
 
      The resolution (granularity) of a clock is returned by the clock_getres()
      system call.  This value is placed in a (non-NULL) *tp.
      Upon successful completion, the value 0 is returned; otherwise the
      value -1 is returned and the global variable errno is set to indicate the
      error.
 

ERRORS

      The following error codes may be set in errno:
 
      [EINVAL]           The clock_id argument was not a valid value.
 
      [EFAULT]           The *tp argument address referenced invalid memory.
 
      [EPERM]            A user other than the super-user attempted to set the
                         time.
      date(1), adjtime(2), ctime(3), timed(8)
 

STANDARDS

      The clock_gettime(), clock_settime(), and clock_getres() system calls
      conform to IEEE Std 1003.1b-1993 (“POSIX.1”).
 

Sections

Based on BSD UNIX
FreeBSD is an advanced operating system for x86 compatible (including Pentium and Athlon), amd64 compatible (including Opteron, Athlon64, and EM64T), UltraSPARC, IA-64, PC-98 and ARM architectures. It is derived from BSD, the version of UNIX developed at the University of California, Berkeley. It is developed and maintained by a large team of individuals. Additional platforms are in various stages of development.