procexec/footprint.c

This is procexec/footprint.c (Listing 24-3, page 522), an example from the book, The Linux Programming Interface.

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

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Function list (Bold in this list means a function is not static)

/* footprint.c

   Using fork() + wait() to control the memory footprint of an application.

   This program contains a function that (artificially) consumes a large
   amount of memory. To avoid changing the process's memory footprint, the
   program creates a child process that calls the function. When the child
   terminates, all of its memory is freed, and the memory consumption of
   the parent is left unaffected.
*/
#define _BSD_SOURCE     /* To get sbrk() declaration from <unistd.h> in case
                           _XOPEN_SOURCE >= 600; defining _SVID_SOURCE or
                           _GNU_SOURCE also suffices */
#include <sys/wait.h>
#include "tlpi_hdr.h"
static int
func(int arg)
{
    int j;

    for (j = 0; j < 0x100; j++)
        if (malloc(0x8000) == NULL)
            errExit("malloc");
    printf("Program break in child:  %10p\n", sbrk(0));

    return arg;
}
int
main(int argc, char *argv[])
{
    int arg = (argc > 1) ? getInt(argv[1], 0, "arg") : 0;
    pid_t childPid;
    int status;

    setbuf(stdout, NULL);           /* Disable buffering of stdout */

    printf("Program break in parent: %10p\n", sbrk(0));

    childPid = fork();
    if (childPid == -1)
        errExit("fork");

    if (childPid == 0)              /* Child calls func() and */
        exit(func(arg));            /* uses return value as exit status */

    /* Parent waits for child to terminate. It can determine the
       result of func() by inspecting 'status' */

    if (wait(&status) == -1)
        errExit("wait");

    printf("Program break in parent: %10p\n", sbrk(0));

    printf("Status = %d %d\n", status, WEXITSTATUS(status));

    exit(EXIT_SUCCESS);
}

 

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