This is timers/cpu_multi_burner.c, an example to accompany the book, The Linux Programming Interface.

This file is not printed in the book; it is a supplementary file for Chapter 23.

The source code file is copyright 2022, Michael Kerrisk, and is licensed under the GNU General Public License, version 3.

In the listing below, the names of Linux system calls and C library functions are hyperlinked to manual pages from the Linux man-pages project, and the names of functions implemented in the book are hyperlinked to the implementations of those functions.


Download timers/cpu_multi_burner.c

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/* cpu_multi_burner.c

   Usage: cpu_multi_burner period...

   This program creates one child process per command-line argument.
   Each child loops consuming CPU, and, after each 'period' seconds
   of consumed CPU, reports its process ID, total CPU time consumed,
   and rate of CPU consumption per real second since the last report.

   For some experiments, it is useful to confine all processes to the
   same CPU, using taskset(1). For example:

        taskset 0x1 ./cpu_multi_burner 2 2

   See also cpu_multithread_burner.c.
#include <sys/times.h>
#include <time.h>
#include "tlpi_hdr.h"

#define NANO 1000000000
static void
burnCPU(float period)
    struct timespec prev_rt;
    if (clock_gettime(CLOCK_REALTIME, &prev_rt) == -1)

    int prev_step = 0;  /* Number of intervals of consumed CPU time calculated
                           in previous loop iteration */

    while (1) {
        struct timespec curr_cpu;
        if (clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &curr_cpu) == -1)

        /* Calculate current number of intervals of consumed CPU time */

        int curr_step = curr_cpu.tv_sec / period +
                        curr_cpu.tv_nsec / period / NANO;

        struct timespec curr_rt;
        if (clock_gettime(CLOCK_REALTIME, &curr_rt) == -1)

        /* Calculate elapsed real microseconds for current CPU interval */

        int elapsed_rt_us = (curr_rt.tv_sec - prev_rt.tv_sec) * 1000000 +
                     (curr_rt.tv_nsec - prev_rt.tv_nsec) / 1000;

        if (curr_step > prev_step) {
            printf("[%ld]  CPU: %.3f; elapsed/cpu = %0.3f; %%CPU = %.3f\n",
                    (long) getpid(),
                    (float) curr_step * period,
                    elapsed_rt_us / 1000000.0 / period,
                    period / (elapsed_rt_us / 1000000.0) * 100.0);
            prev_step = curr_step;
            prev_rt = curr_rt;
main(int argc, char *argv[])
    if (argc < 2 || strcmp(argv[1], "--help") == 0)
        usageErr("%s [period]...\n"
                "Creates one process per argument that reports "
                "CPU time each 'period' CPU seconds\n"
                "'period' can be a floating-point number\n", argv[0]);

    int nproc = argc - 1;

    for (int j = 0; j < nproc; j++) {
        float period;

        switch (fork()) {
        case 0:
            sscanf(argv[j + 1], "%f", &period);
            exit(EXIT_SUCCESS);         /* NOTREACHED */

        case -1:





Download timers/cpu_multi_burner.c

Note that, in most cases, the programs rendered in these web pages are not free standing: you'll typically also need a few other source files (mostly in the lib/ subdirectory) as well. Generally, it's easier to just download the entire source tarball and build the programs with make(1). By hovering your mouse over the various hyperlinked include files and function calls above, you can see which other source files this file depends on.

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