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Tcl_GetTime(3)              Tcl Library Procedures              Tcl_GetTime(3)




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

       Points  to  memory  in  which  to  store the date and time information.
       Pointer to handler function replacing Tcl_GetTime's access to  the  OS.
       Pointer  to  handler  function for the conversion of time delays in the
       virtual domain to real-time.  Value passed through to the  two  handler
       functions.  Pointer to place the currently registered get handler func-
       tion into.  Pointer to place the  currently  registered  scale  handler
       function  into.  Pointer to place the currently registered pass-through
       value into.


DESCRIPTION

       The Tcl_GetTime function retrieves  the  current  time  as  a  Tcl_Time
       structure  in  memory the caller provides.  This structure has the fol-
       lowing 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 regard-
       less 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 pre-
       cise  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.)

       The  Tcl_SetTime  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  vir-
       tual domain into real time.

       The  Tcl_QueryTime  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.

       Any  handler  pair  specified  has  to  return data which is consistent
       between them. In other words, setting one handler of the pair to  some-
       thing  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  back-
       wards,  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 behaviour of the Tcl core with  regard  to  this  situation,
       i.e. the existing behaviour is retained.


SEE ALSO

       clock(n)


KEYWORDS

       date, time



Tcl                                   8.4                       Tcl_GetTime(3)

GetTime 8.5.4 - Generated Tue Aug 19 08:28:07 CDT 2008
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