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clock(3) [centos man page]

CLOCK(3)						     Linux Programmer's Manual							  CLOCK(3)

clock - determine processor time SYNOPSIS
#include <time.h> clock_t clock(void); DESCRIPTION
The clock() function returns an approximation of processor time used by the program. RETURN VALUE
The value returned is the CPU time used so far as a clock_t; to get the number of seconds used, divide by CLOCKS_PER_SEC. If the processor time used is not available or its value cannot be represented, the function returns the value (clock_t) -1. CONFORMING TO
C89, C99, POSIX.1-2001. POSIX requires that CLOCKS_PER_SEC equals 1000000 independent of the actual resolution. NOTES
The C standard allows for arbitrary values at the start of the program; subtract the value returned from a call to clock() at the start of the program to get maximum portability. Note that the time can wrap around. On a 32-bit system where CLOCKS_PER_SEC equals 1000000 this function will return the same value approximately every 72 minutes. On several other implementations, the value returned by clock() also includes the times of any children whose status has been collected via wait(2) (or another wait-type call). Linux does not include the times of waited-for children in the value returned by clock(). The times(2) function, which explicitly returns (separate) information about the caller and its children, may be preferable. SEE ALSO
clock_gettime(2), getrusage(2), times(2) COLOPHON
This page is part of release 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at GNU
2008-08-28 CLOCK(3)

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clock(3)						     Library Functions Manual							  clock(3)

clock - Reports CPU time used LIBRARY
Standard C Library (, libc.a) SYNOPSIS
#include <time.h> clock_t clock (void); STANDARDS
Interfaces documented on this reference page conform to industry standards as follows: clock(): XPG4, XPG4-UNIX Refer to the standards(5) reference page for more information about industry standards and associated tags. DESCRIPTION
The clock() function reports the amount of processor time used by the calling process and each of its terminated child processes for which a wait function has been executed. When a child process does not wait for its children, its child-process times are not included in its times. RETURN VALUES
The clock() function returns the amount of processor time (in microseconds) used since the first call to clock(). To convert the time to seconds, divide it by CLOCKS_PER_SEC (which is defined to be 1,000,000 in <time.h>). If the processor time used is not available or its value cannot be represented, the clock() function returns (clock_t)-1. RELATED INFORMATION
Functions: ctime(3), getrusage(2), times(3), wait(2) Standards: standards(5) delim off clock(3)
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