correct the time to allow synchronization of the
Standard C Library (libc, -lc)
struct timeval *delta
() system call makes small
adjustments to the system time, as returned by
advancing or retarding it by the time specified by the timeval
is negative, the clock is slowed down
by incrementing it more slowly than normal until the correction is complete.
is positive, a larger increment than
normal is used. The skew used to perform the correction is generally a
fraction of one percent. Thus, the time is always a monotonically increasing
function. A time correction from an earlier call to
() may not be finished when
() is called again. If
is not a null pointer, the structure
pointed to will contain, upon return, the number of microseconds still to be
corrected from the earlier call.
This call may be used by time servers that synchronize the clocks of computers
in a local area network. Such time servers would slow down the clocks of some
machines and speed up the clocks of others to bring them to the average
() system call is restricted to
() function returns the
value 0 if successful; otherwise the value -1 is returned and
the global variable errno
is set to indicate
() system call will fail if:
- An argument points outside the process's allocated address space.
- The process's effective user ID is not that of the super-user.
R. Gusella and
S. Zatti, TSP: The Time
Synchronization Protocol for UNIX 4.3BSD.
() system call appeared in