/*************************************************************************\
*                  Copyright (C) Michael Kerrisk, 2026.                   *
*                                                                         *
* This program is free software. You may use, modify, and redistribute it *
* under the terms of the GNU General Public License as published by the   *
* Free Software Foundation, either version 3 or (at your option) any      *
* later version. This program is distributed without any warranty.  See   *
* the file COPYING.gpl-v3 for details.                                    *
\*************************************************************************/

/* process_time.c

   Demonstrate usage of clock(3) and times(2) to retrieve process virtual times.

   Usage: process_time [num-calls]

   Make 'num-calls' calls to getppid(), and then display process times.
*/
#include <sys/times.h>
#include <time.h>
#include "tlpi_hdr.h"

static void             /* Display 'msg' and process times */
displayProcessTimes(const char *msg)
{
    struct tms t;
    clock_t clockTime;
    static long clockTicks = 0;

    if (msg != NULL)
        printf("%s", msg);

    if (clockTicks == 0) {      /* Fetch clock ticks on first call */
        clockTicks = sysconf(_SC_CLK_TCK);
        if (clockTicks == -1)
            errExit("sysconf");
    }

    clockTime = clock();
    if (clockTime == -1)
        errExit("clock");

    printf("        clock() returns: %ld clocks-per-sec (%.2f secs)\n",
            (long) clockTime, (double) clockTime / CLOCKS_PER_SEC);

    if (times(&t) == -1)
        errExit("times");
    printf("        times() yields: user CPU=%.2f; system CPU: %.2f\n",
            (double) t.tms_utime / clockTicks,
            (double) t.tms_stime / clockTicks);
}

int
main(int argc, char *argv[])
{
    int numCalls, j;

    printf("CLOCKS_PER_SEC=%ld  sysconf(_SC_CLK_TCK)=%ld\n\n",
            (long) CLOCKS_PER_SEC, sysconf(_SC_CLK_TCK));

    displayProcessTimes("At program start:\n");

    /* Call getppid() a large number of times, so that
       some user and system CPU time are consumed */

    numCalls = (argc > 1) ? getInt(argv[1], GN_GT_0, "num-calls") : 100000000;
    for (j = 0; j < numCalls; j++)
        (void) getppid();

    displayProcessTimes("After getppid() loop:\n");

    exit(EXIT_SUCCESS);
}