Tcl_GetTime(3)              Tcl Library Procedures              Tcl_GetTime(3)

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NAME
       Tcl_GetTime, Tcl_SetTimeProc, Tcl_QueryTimeProc - get date and time

SYNOPSIS
       #include <tcl.h>

       Tcl_GetTime(timePtr)

       Tcl_SetTimeProc(getProc, scaleProc, clientData)

       Tcl_QueryTimeProc(getProcPtr, scaleProcPtr, clientDataPtr)

ARGUMENTS
       Tcl_Time *timePtr (out)                Points to memory in which to
                                              store the date and time
                                              information.

       Tcl_GetTimeProc getProc (in)           Pointer to handler function
                                              replacing Tcl_GetTime's access
                                              to the OS.

       Tcl_ScaleTimeProc scaleProc (in)       Pointer to handler function for
                                              the conversion of time delays in
                                              the virtual domain to real-time.

       ClientData clientData (in)             Value passed through to the two
                                              handler functions.

       Tcl_GetTimeProc *getProcPtr (out)      Pointer to place the currently
                                              registered get handler function
                                              into.

       Tcl_ScaleTimeProc *scaleProcPtr (out)  Pointer to place the currently
                                              registered scale handler
                                              function into.

       ClientData *clientDataPtr (out)        Pointer to place the currently
                                              registered pass-through value
                                              into.
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DESCRIPTION
       The Tcl_GetTime function retrieves the current time as a Tcl_Time
       structure in memory the caller provides.  This structure has the
       following definition:

              typedef struct Tcl_Time {
                  long sec;
                  long usec;
              } Tcl_Time;

       On return, the sec member of the structure is filled in with the number
       of seconds that have elapsed since the epoch: the epoch is the point in
       time of 00:00 UTC, 1 January 1970.  This number does not count leap
       seconds - an interval of one day advances it by 86400 seconds
       regardless of whether a leap second has been inserted.

       The usec member of the structure is filled in with the number of
       microseconds that have elapsed since the start of the second designated
       by sec.  The Tcl library makes every effort to keep this number as
       precise as possible, subject to the limitations of the computer system.
       On multiprocessor variants of Windows, this number may be limited to
       the 10- or 20-ms granularity of the system clock.  (On single-processor
       Windows systems, the usec field is derived from a performance counter
       and is highly precise.)

   VIRTUALIZED TIME
       The Tcl_SetTimeProc function registers two related handler functions
       with the core. The first handler function is a replacement for
       Tcl_GetTime, or rather the OS access made by Tcl_GetTime. The other
       handler function is used by the Tcl notifier to convert wait/block
       times from the virtual domain into real time.

       The Tcl_QueryTimeProc function returns the currently registered handler
       functions. If no external handlers were set then this will return the
       standard handlers accessing and processing the native time of the OS.
       The arguments to the function are allowed to be NULL; and any argument
       which is NULL is ignored and not set.

       The signatures of the handler functions are as follows:

              typedef void Tcl_GetTimeProc(
                      Tcl_Time *timebuf,
                      ClientData clientData);
              typedef void Tcl_ScaleTimeProc(
                      Tcl_Time *timebuf,
                      ClientData clientData);

       The timebuf fields contain the time to manipulate, and the clientData
       fields contain a pointer supplied at the time the handler functions
       were registered.

       Any handler pair specified has to return data which is consistent
       between them. In other words, setting one handler of the pair to
       something assuming a 10-times slowdown, and the other handler of the
       pair to something assuming a two-times slowdown is wrong and not
       allowed.

       The set handler functions are allowed to run the delivered time
       backwards, however this should be avoided. We have to allow it as the
       native time can run backwards as the user can fiddle with the system
       time one way or other. Note that the insertion of the hooks will not
       change the behavior of the Tcl core with regard to this situation, i.e.
       the existing behavior is retained.

SEE ALSO
       clock(n)

KEYWORDS
       date, time

Tcl                                   8.4                       Tcl_GetTime(3)