Follow Techotopia on Twitter

On-line Guides
All Guides
eBook Store
iOS / Android
Linux for Beginners
Office Productivity
Linux Installation
Linux Security
Linux Utilities
Linux Virtualization
Linux Kernel
System/Network Admin
Programming
Scripting Languages
Development Tools
Web Development
GUI Toolkits/Desktop
Databases
Mail Systems
openSolaris
Eclipse Documentation
Techotopia.com
Virtuatopia.com

How To Guides
Virtualization
General System Admin
Linux Security
Linux Filesystems
Web Servers
Graphics & Desktop
PC Hardware
Windows
Problem Solutions
Privacy Policy

  




 

 

21.3.1 CPU Time Inquiry

To get a process' CPU time, you can use the clock function. This facility is declared in the header file time.h. In typical usage, you call the clock function at the beginning and end of the interval you want to time, subtract the values, and then divide by CLOCKS_PER_SEC (the number of clock ticks per second) to get processor time, like this:

     #include <time.h>
     
     clock_t start, end;
     double cpu_time_used;
     
     start = clock();
     ... /* Do the work. */
     end = clock();
     cpu_time_used = ((double) (end - start)) / CLOCKS_PER_SEC;

Do not use a single CPU time as an amount of time; it doesn't work that way. Either do a subtraction as shown above or query processor time directly. See Processor Time.

Different computers and operating systems vary wildly in how they keep track of CPU time. It's common for the internal processor clock to have a resolution somewhere between a hundredth and millionth of a second.

— Macro: int CLOCKS_PER_SEC

The value of this macro is the number of clock ticks per second measured by the clock function. POSIX requires that this value be one million independent of the actual resolution.

— Macro: int CLK_TCK

This is an obsolete name for CLOCKS_PER_SEC.

— Data Type: clock_t

This is the type of the value returned by the clock function. Values of type clock_t are numbers of clock ticks.

— Function: clock_t clock (void)

This function returns the calling process' current CPU time. If the CPU time is not available or cannot be represented, clock returns the value (clock_t)(-1).


 
 
  Published under the terms of the GNU General Public License Design by Interspire