clock_t

 

C

Compiler support

Language

Headers

Type support

Program utilities

Variadic function support

Error handling

Dynamic memory management

Strings library

Algorithms

Numerics

Date and time utilities

Input/output support

Localization support

Concurrency support (C11)

Technical Specifications

Symbol index

 

Date and time utilities

Functions

Time manipulation

difftime

time

clock

timespec_get (C11)

timespec_getres (C23)

Format conversions

asctimeasctime_s (deprecated in C23)(C11)

ctimectime_s (deprecated in C23)(C11)

strftime

wcsftime (C95)

gmtimegmtime_rgmtime_s (C23)(C11)

localtimelocaltime_rlocaltime_s (C23)(C11)

mktime

Constants

CLOCKS_PER_SEC

Types

tm

time_t

clock_t

timespec (C11)

 

Defined in header <time.h>
typedef /* unspecified */ clock_t;

Arithmetic(until C11)Real(since C11) type capable of representing the processor time used by a process. It has implementation-defined range and precision.

Example

Run this code

#include <stdio.h>
#include <time.h>
#include <math.h>
 
volatile double sink;
int main (void)
{
  clock_t start = clock();
 
  for(size_t i=0; i<3141592; ++i)
      sink+=sin(i);
 
  clock_t end = clock();
  double cpu_time_used = ((double) (end - start)) / CLOCKS_PER_SEC;
 
  printf("for loop took %f seconds to execute \n", cpu_time_used);
}

Possible output:

for loop took 0.271828 seconds to execute

References

• C17 standard (ISO/IEC 9899:2018):

• 7.27.1/3 Components of time (p: 284)

• C11 standard (ISO/IEC 9899:2011):

• 7.27.1/3 Components of time (p: 388)

• C99 standard (ISO/IEC 9899:1999):

• 7.23.1/3 Components of time (p: 338)

• C89/C90 standard (ISO/IEC 9899:1990):

• 4.12.1 Components of time

See also

clock	returns raw processor clock time since the program is started (function)
CLOCKS_PER_SEC	number of processor clock ticks per second (macro constant)
C++ documentation for clock_t