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/*
* Print the process reaper id.
*
* Copyright (c) 2020 Dmitry V. Levin <ldv@strace.io>
* All rights reserved.
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include "tests.h"
#include <stdio.h>
#include <unistd.h>
#include <sys/wait.h>
/* PARENT - CHILD - GRANDCHILD */
static int
grandchild(int read_fd, int write_fd)
{
/* wait for notification from PARENT about CHILD completion */
pid_t pid;
if (read(read_fd, &pid, sizeof(pid)) != 0)
perror_msg_and_fail("read");
/* write ppid to PARENT */
pid = getppid();
if (write(write_fd, &pid, sizeof(pid)) != sizeof(pid))
perror_msg_and_fail("write");
_exit(0);
}
static int
child(int read_fd, int write_fd)
{
pid_t pid = fork();
if (pid < 0)
perror_msg_and_fail("fork");
if (!pid)
return grandchild(read_fd, write_fd);
else
_exit(0);
}
static int
parent(pid_t pid, int read_fd, int write_fd)
{
/* wait for CHILD completion */
int status;
if (waitpid(pid, &status, 0) != pid)
perror_msg_and_fail("waitpid");
if (status != 0)
error_msg_and_fail("status %x", status);
/* notify GRANDCHILD about CHILD completion */
close(write_fd),
write_fd = -1;
/* read ppid of GRANDCHILD */
if (read(read_fd, &pid, sizeof(pid)) != sizeof(pid))
perror_msg_and_fail("read");
printf("%d\n", pid);
return 0;
}
int
main(void)
{
int parent_grandchild_fds[2];
#define parent_read_fd parent_grandchild_fds[0]
#define grandchild_write_fd parent_grandchild_fds[1]
int grandchild_parent_fds[2];
#define grandchild_read_fd grandchild_parent_fds[0]
#define parent_write_fd grandchild_parent_fds[1]
if (pipe(parent_grandchild_fds) ||
pipe(grandchild_parent_fds))
perror_msg_and_fail("pipe");
pid_t pid = fork();
if (pid < 0)
perror_msg_and_fail("fork");
if (!pid) {
/* CHILD */
close(parent_read_fd),
parent_read_fd = -1;
close(parent_write_fd),
parent_write_fd = -1;
return child(grandchild_read_fd,
grandchild_write_fd);
} else {
/* PARENT */
close(grandchild_read_fd),
grandchild_read_fd = -1;
close(grandchild_write_fd),
grandchild_write_fd = -1;
return parent(pid, parent_read_fd,
parent_write_fd);
}
}
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