60 lines
1.6 KiB
C
60 lines
1.6 KiB
C
/* This file is part of the sample code and exercises
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* used by the class "Advanced Programming in the UNIX
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* Environment" taught by Jan Schaumann
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* <jschauma@netmeister.org> at Stevens Institute of
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* Technology.
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*
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* This file is in the public domain.
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*
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* You don't have to, but if you feel like
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* acknowledging where you got this code, you may
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* reference me by name, email address, or point
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* people to the course website:
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* https://stevens.netmeister.org/631/
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*/
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/* This program illustrates how zombies are created, and how they
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* disappear again. If you like, you can try killing some of the zombies.
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*/
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#include <sys/wait.h>
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#include <err.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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int
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main() {
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(void)printf("Let's create some zombies!\n");
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for (int i=0; i<5; i++) {
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pid_t pid;
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if ((pid = fork()) < 0) {
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err(EXIT_FAILURE, "fork error");
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/* NOTREACHED */
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}
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if (pid == 0) {
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/* Do nothing in the child, i.e. immediately exit. This
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* creates a zombie until the parent decides to wait for
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* the child. */
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exit(EXIT_SUCCESS);
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} else {
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(void)printf("====\n");
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system("ps a | grep '[^ ]'a.ou[t]");
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/* We don't wait for our children. This allows
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* them to become zombies. We sleep for a short
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* time to delay the next iteration of the loop.
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* When the parent exits, init will reap the zombies. */
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sleep(1);
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}
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}
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(void)printf("I'm going to sleep - try to kill my zombie children, if you like.\n");
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sleep(30);
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(void)printf("That's enough zombies. Let's have init clean them up.\n");
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(void)printf("Remember to run 'ps a | grep a.ou[t]' to verify.\n");
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return EXIT_SUCCESS;
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}
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