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clock(3p) [centos man page]

CLOCK(3P)						     POSIX Programmer's Manual							 CLOCK(3P)

PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the correspond- ing Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. NAME
clock - report CPU time used SYNOPSIS
#include <time.h> clock_t clock(void); DESCRIPTION
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. 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. ERRORS
No errors are defined. The following sections are informative. EXAMPLES
None. APPLICATION USAGE
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. The value returned by clock() may wrap around on some implementations. For example, on a machine with 32-bit values for clock_t, it wraps after 2147 seconds or 36 minutes. RATIONALE
None. FUTURE DIRECTIONS
None. SEE ALSO
asctime(), ctime(), difftime(), gmtime(), localtime(), mktime(), strftime(), strptime(), time(), utime(), the Base Definitions volume of IEEE Std 1003.1-2001, <time.h> COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol- ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html . IEEE
/The Open Group 2003 CLOCK(3P)

Check Out this Related Man Page

PTHREAD_GETCPUCLOCKID(3P)				     POSIX Programmer's Manual					 PTHREAD_GETCPUCLOCKID(3P)

PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the correspond- ing Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. NAME
pthread_getcpuclockid - access a thread CPU-time clock (ADVANCED REALTIME THREADS) SYNOPSIS
#include <pthread.h> #include <time.h> int pthread_getcpuclockid(pthread_t thread_id, clockid_t *clock_id); DESCRIPTION
The pthread_getcpuclockid() function shall return in clock_id the clock ID of the CPU-time clock of the thread specified by thread_id, if the thread specified by thread_id exists. RETURN VALUE
Upon successful completion, pthread_getcpuclockid() shall return zero; otherwise, an error number shall be returned to indicate the error. ERRORS
The pthread_getcpuclockid() function may fail if: ESRCH The value specified by thread_id does not refer to an existing thread. The following sections are informative. EXAMPLES
None. APPLICATION USAGE
The pthread_getcpuclockid() function is part of the Thread CPU-Time Clocks option and need not be provided on all implementations. RATIONALE
None. FUTURE DIRECTIONS
None. SEE ALSO
clock_getcpuclockid(), clock_getres(), timer_create(), the Base Definitions volume of IEEE Std 1003.1-2001, <pthread.h>, <time.h> COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol- ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html . IEEE
/The Open Group 2003 PTHREAD_GETCPUCLOCKID(3P)

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