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#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <err.h>
#include <fcntl.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#define die(...) err(EXIT_FAILURE, __VA_ARGS__)
static void chld(void);
static void prnt(void);
int
main(void)
{
pid_t pid;
switch (pid = fork()) {
case -1:
die("fork");
case 0:
chld();
break;
default:
prnt();
}
return EXIT_SUCCESS;
}
void
chld(void)
{
int fd;
sleep(1);
if ((fd = open("foo", O_WRONLY)) == -1)
die("open: foo");
if (write(fd, "overwritten", sizeof("overwritten") - 1) == -1)
die("write");
close(fd);
}
void
prnt(void)
{
int fd;
char *buf;
struct stat sb;
if ((fd = open("foo", O_RDONLY)) == -1)
die("open: foo");
if (fstat(fd, &sb) == -1)
die("fstat: foo");
if ((buf = mmap(NULL, sb.st_size, PROT_READ, MAP_PRIVATE, fd, 0))
== MAP_FAILED)
die("mmap");
wait(NULL);
write(STDOUT_FILENO, buf, sb.st_size);
munmap(buf, sb.st_size);
close(fd);
}
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