отчет об использовании времени ЦП (report CPU time used)
Пролог (Prolog)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
Имя (Name)
clock — report CPU time used
Синопсис (Synopsis)
#include <time.h>
clock_t clock(void);
Описание (Description)
The functionality described on this reference page is aligned
with the ISO C standard. Any conflict between the requirements
described here and the ISO C standard is unintentional. This
volume of POSIX.1‐2017 defers to the ISO C standard.
The clock() function shall return the implementation's best
approximation to the processor time used by the process since the
beginning of an implementation-defined era related only to the
process invocation.
Возвращаемое значение (Return value)
To determine the time in seconds, the value returned by clock()
should be divided by the value of the macro CLOCKS_PER_SEC.
CLOCKS_PER_SEC is defined to be one million in <time.h>. If the
processor time used is not available or its value cannot be
represented, the function shall return the value (clock_t)-1.
Ошибки (Error)
No errors are defined.
The following sections are informative.
Примеры (Examples)
None.
Использование в приложениях (Application usage)
In programming environments where clock_t is a 32-bit integer
type and CLOCKS_PER_SEC is one million, clock() will start
failing in less than 36 minutes of processor time for signed
clock_t, or 72 minutes for unsigned clock_t. Applications
intended to be portable to such environments should use times()
instead (or clock_gettime() with CLOCK_PROCESS_CPUTIME_ID, if
supported).
In order to measure the time spent in a program, clock() should
be called at the start of the program and its return value
subtracted from the value returned by subsequent calls. The value
returned by clock() is defined for compatibility across systems
that have clocks with different resolutions. The resolution on
any particular system need not be to microsecond accuracy.
Обоснование (Rationale)
None.
Будущие направления (Future directions)
None.
Смотри также (See also)
asctime(3p), clock_getres(3p), ctime(3p), difftime(3p),
gmtime(3p), localtime(3p), mktime(3p), strftime(3p),
strptime(3p), time(3p), times(3p), utime(3p)
The Base Definitions volume of POSIX.1‐2017, time.h(0p)
