1CLOCK(3) Linux Programmer's Manual CLOCK(3)
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6 clock - Determine processor time
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9 #include <time.h>
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11 clock_t clock(void);
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14 The clock() function returns an approximation of processor time used by
15 the program.
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18 The value returned is the CPU time used so far as a clock_t; to get the
19 number of seconds used, divide by CLOCKS_PER_SEC. If the processor
20 time used is not available or its value cannot be represented, the
21 function returns the value (clock_t)-1.
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24 C89, C99, POSIX.1-2001. POSIX requires that CLOCKS_PER_SEC equals
25 1000000 independent of the actual resolution.
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28 The C standard allows for arbitrary values at the start of the program;
29 subtract the value returned from a call to clock() at the start of the
30 program to get maximum portability.
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32 Note that the time can wrap around. On a 32bit system where
33 CLOCKS_PER_SEC equals 1000000 this function will return the same value
34 approximately every 72 minutes.
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36 On several other implementations, the value returned by clock() also
37 includes the times of any children whose status has been collected via
38 wait() (or another wait-type call). Linux does not include the times
39 of waited-for children in the value returned by clock(). The times()
40 function, which explicitly returns (separate) information about the
41 caller and its children, may be preferable.
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44 getrusage(2), times(2)
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48GNU 2002-06-14 CLOCK(3)