times() — Get process and child process times

Standards

Standards / Extensions	C or C++	Dependencies
POSIX.1 XPG4 XPG4.2 Single UNIX Specification, Version 3	both

Format

#define _POSIX_SOURCE
#include <sys/times.h>

clock_t times(struct tms *buffer);

General description

Gets processor times of interest to a process.

struct tms *buffer: Points to a memory location where times() can store a structure of information describing processor time used by the current process and other related processes.

times() returns information in a tms structure, which has the following elements:

clock_t tms_utime: Amount of processor time used by instructions in the calling process.
Under z/OS® UNIX, this does not include processor time spent running in the kernel. It does include any processor time accumulated for the address space before it became a z/OS UNIX process.
clock_t tms_stime: Amount of processor time used by the system.
Under z/OS UNIX, this value represents kernel busy time running on behalf of the calling process. It does not include processor time performing other MVS™ system functions on behalf of the process.
clock_t tms_cutime: The sum of tms_utime and tms_cutime values for all waited-for child processes which have terminated.
clock_t tms_cstime: The sum of tms_stime and tms_cstime values for all terminated child processes of the calling process.

clock_t is an integral type determined in the time.h header file. It measures times in terms of clock ticks. The number of clock ticks in a second (for your installation) can be found in sysconf(_SC_CLK_TCK).

Times for a terminated child can be determined once wait() or waitpid() have reported the child's termination.

Pthreads can not be separately clocked by the times() function because they do not run in a separate process like forked children do.

Returned value

If successful, times() returns a value giving the elapsed time since the process was last invoked (for example, at system startup). If this time value cannot be determined, times() returns (clock_t)-1.

If unsuccessful, times() sets errno to one of the following values:

Error Code: Description
ERANGE: An overflow having occurred computing time values.

Example

CELEBT12

/* CELEBT12

   This example provides the amount of processor time
   used by instructions and the system for the parent and child
   processes.

 */
#define _POSIX_SOURCE
#include <sys/times.h>
#include <time.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <stdio.h>
#include <unistd.h>

main() {
  int status;
  long i, j;
  struct tms t;
  clock_t dub;

  int tics_per_second;

  tics_per_second = sysconf(_SC_CLK_TCK);

  if (fork() == 0) {
    for (i=0, j=0; i<1000000; i++)
       j += i;
    exit(0);
  }

  if (wait(&status) == -1)
    perror("wait() error");
  else if (!WIFEXITED(status))
    puts("Child did not exit successfully");
  else if ((dub = times(&t)) == -1)
    perror("times() error");
  else {
    printf("process was dubbed %f seconds ago.\n\n",
           ((double) dub)/tics_per_second);
    printf("            utime           stime\n");
    printf("parent:    %f        %f\n",
           ((double) t.tms_utime)/tics_per_second,
           ((double) t.tms_stime)/tics_per_second);
    printf("child:     %f        %f\n",
           ((double) t.tms_cutime)/tics_per_second,
           ((double) t.tms_cstime)/tics_per_second);
  }
}

Output

process was dubbed 1.600000 seconds ago.

            utime           stime
parent:    0.000000        0.020000
child:     0.320000        0.000000