times

times

Determine Process Times

Portability: POSIX.1 conforming, UNIX compatible

SYNOPSIS
DESCRIPTION
RETURN VALUE
EXAMPLE
RELATED FUNCTIONS

SYNOPSIS

#include <time.h>

clock_t times(struct tms *buffer);

DESCRIPTION

times stores user and system CPU time for a process and its children. The time information is stored in a tms structure located at the address pointed to by buffer . The tms structure contains the following members:

clock_t tms_utime: is the amount of CPU time used by instructions in the calling process. Under OS/390 USS, this does not include time used by instructions in the kernel; however, it does include CPU time for the address space before it became a process.
clock_t tms_stime: is the amount of CPU time used by the system on behalf of the calling process. Under OS/390 USS, this value represents kernel time used for the calling process. It does not include time spent calling other system functions on behalf of the calling process.
clock_t tms_cutime: is the total user time for all terminated child processes. This value is calculated by summing the tms_utime and tms_cutime values for all child processes that have terminated.
clock_t tms_cstime: is the total system time for all terminated child processes. This value is calculated by summing the tms_stime and tms_cstime values for all child processes that have terminated.

The clock_t type measures time in clock ticks. The amount of time represented by each clock tick is determined by the CLK_TCK symbol, which is defined in time.h .

RETURN VALUE

If successful, times returns a positive value representing elapsed time, and ((clock_t) -1) if it is unsuccessful. The elapsed time value is referenced from an arbitrary point; hence, it is only useful when making more than one call to times .

Note: USS computes elapsed time values using fullword (long) arithmetic. If this computation overflows, times indicates an error and sets errno to ERANGE . [cautionend]

EXAMPLE

The following example illustrates the use of times to determine process times:

#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <time.h>
#include <times.h>
#include <stdio.h>
#include <stdlib.h>

int main(void)
  {
   int i, status;
   pid_t pid;
   time_t currentTime;
   struct tms cpuTime;

   if ((pid = fork()) == -1) {         /* Start a child process.   */
        perror("fork error");
        exit(EXIT_FAILURE);
   }
   else if (pid == 0) {                /* This is the child.       */
      time(&currentTime);
      printf("Child process started at %s", ctime(&currentTime));
      for (i = 0; i < 5; ++i) {
         printf("Counting: %dn", i);  /* count for 5 seconds.     */
         sleep(1);
      }
      time(&currentTime);
      printf("Child process ended at %s", ctime(&currentTime));
      exit(EXIT_SUCCESS);
   }
   else {                              /* This is the parent.      */
      time(&currentTime);
      printf("Parent process started at %s", ctime(&currentTime));

      if (wait(&status) == -1 )        /* Wait for child process.  */
         perror("wait error");
      if (WIFEXITED(status))
           printf("Child process ended normally.n");
      else
         printf("Child process did not end normally.n");

      if (times(&cpuTime) < 0)         /* Get process times.       */
         perror("times error");
      else {
         printf("Parent process user time = %fn",
              ((double) cpuTime.tms_utime)/CLK_TCK);
         printf("Parent process system time = %fn",
              ((double) cpuTime.tms_stime)/CLK_TCK);
         printf("Child process user time = %fn",
              ((double) cpuTime.tms_cutime)/CLK_TCK);
         printf("Child process system time = %fn",
              ((double) cpuTime.tms_cstime)/CLK_TCK);
      }
      time(&currentTime);
      printf("Parent process ended at %s", ctime(&currentTime));
      exit(EXIT_SUCCESS);
   }
}

RELATED FUNCTIONS

clock

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