procexec/footprint.c

+/* 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);
 }