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clock(3c)

clock(3C)                Standard C Library Functions                clock(3C)

NAME
       clock - report CPU time used

SYNOPSIS
       #include <time.h>

       clock_t clock(void);

DESCRIPTION
       The  clock()  function returns the amount of CPU time (in microseconds)
       used since the first call to clock() in the calling process.  The  time
       reported is the sum of the user and system times of the calling process
       and  its  terminated  child  processes  for  which  it has executed the
       wait(3C) function, the pclose(3C) function, or the system(3C) function.

RETURN VALUES
       Dividing the value returned by clock() by the constant  CLOCKS_PER_SEC,
       defined  in  the <time.h> header, will give the time in seconds. If the
       process time used is not available or cannot be represented, clock  re‐
       turns the value (clock_t) −1.

USAGE
       The  value  returned by clock() is defined in microseconds for compati‐
       bility with systems that have CPU clocks with much  higher  resolution.
       This  value  is  a 32-bit value in 32-bit code, and so will wrap around
       after accumulating only 2147 seconds of CPU time  (about  36  minutes).
       The  returned value is a 64-bit value in 64-bit code, and does not suf‐
       fer from the same short overflow period.


       In either case, but particularly for 32-bit code, the use  of  times(2)
       or  clock_gettime(3C) with CLOCK_PROCESS_CPUTIME_ID is recommended over
       having to handle wrap around with this function.

ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:

       tab() box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) ATTRIBUTE  TYPEAT‐
       TRIBUTE  VALUE _ Interface StabilityCommitted _ MT-LevelMT-Safe _ Stan‐
       dardSee standards(7).


SEE ALSO
       times(2), clock_gettime(3C), popen(3C), system(3C),  wait(3C),  attrib‐
       utes(7), standards(7)

HISTORY
       The  clock()  function has been included in all Sun and Oracle releases
       of Solaris.

Oracle Solaris 11.4               27 Aug 2025                        clock(3C)
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