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#define _GNU_SOURCE
#include <sys/wait.h>
#include <assert.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <paths.h>
#include <stdio.h>
#include <unistd.h>
int
main(void)
{
int fd, nfd;
if ((fd = open(_PATH_DEVNULL, O_RDONLY | O_CLOEXEC)) == -1)
err(1, "open: %s", _PATH_DEVNULL);
if ((nfd = dup(fd)) == -1)
err(1, "dup");
assert((fcntl(nfd, F_GETFD) & FD_CLOEXEC) == 0);
close(nfd);
if (dup3(fd, nfd, O_CLOEXEC) == -1)
err(1, "dup");
assert((fcntl(nfd, F_GETFD) & FD_CLOEXEC) != 0);
close(nfd);
switch (fork()) {
case -1:
err(1, "fork");
case 0:
puts("If the FD for /dev/null is closed, this should list 4 items");
fflush(stdout);
execlp("ls", "ls", "/proc/self/fd", NULL);
err(1, "exec: true");
default:
if (wait(NULL) == -1)
err(1, "wait");
}
/* Not EBADF */
assert(close(fd) == 0);
}
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