/* $OpenBSD: stdfiles.c,v 1.4 2016/09/01 10:56:45 deraadt Exp $ */
/* PUBLIC DOMAIN Oct 2002 Marco S Hyman <marc@snafu.org> */

#include <assert.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>

/*
 * test what happens to blocking/non-blocking mode on stdout/stderr when
 * it is changed on stdin.   A comment in the pthreads code implies that
 * all three files are linked.   Check it out.
 */

int
main(int argc, char *argv[])
{
        int dup_stdout;
        int stdin_flags;
        int stdout_flags;
        int dup_flags;
        int stderr_flags;
        int new_flags;
        int new_fd;

        /* dup stdout for the fun of it. */
        dup_stdout = dup(STDOUT_FILENO);

        /* read std in/out/err flags */
        stdin_flags = fcntl(STDIN_FILENO, F_GETFL);
        assert(stdin_flags != -1);
        stdout_flags = fcntl(STDOUT_FILENO, F_GETFL);
        assert(stdout_flags != -1);
        dup_flags = fcntl(dup_stdout, F_GETFL);
        assert(dup_flags != -1);
        stderr_flags = fcntl(STDERR_FILENO, F_GETFL);
        assert(stderr_flags != -1);
        printf("starting flags: in = %x, out = %x, dup = %x, err = %x\n",
               stdin_flags, stdout_flags, dup_flags, stderr_flags);

        /* set stdin to non-blocking mode and see if stdout/stderr change */
        new_flags = stdin_flags | O_NONBLOCK;
        printf("forcing stdin to O_NONBLOCK (flags %x)\n", new_flags);
        assert(fcntl(STDIN_FILENO, F_SETFL, new_flags) != -1);

        new_flags = fcntl(STDIN_FILENO, F_GETFL);
        assert(new_flags != -1);
        if (new_flags != stdin_flags) {
                printf("stdin flags changed %x -> %x\n", stdin_flags,
                       new_flags);
                stdin_flags = new_flags;
        }

        new_flags = fcntl(STDOUT_FILENO, F_GETFL);
        assert(new_flags != -1);
        if (new_flags != stdout_flags) {
                printf("stdout flags changed %x -> %x\n", stdout_flags,
                       new_flags);
                stdout_flags = new_flags;
        }

        new_flags = fcntl(dup_stdout, F_GETFL);
        assert(new_flags != -1);
        if (new_flags != dup_flags) {
                printf("dup_stdout flags changed %x -> %x\n", dup_flags,
                       new_flags);
                dup_flags = new_flags;
        }

        new_flags = fcntl(STDERR_FILENO, F_GETFL);
        assert(new_flags != -1);
        if (new_flags != stderr_flags) {
                printf("stderr flags changed %x -> %x\n", stderr_flags,
                       new_flags);
                stderr_flags = new_flags;
        }

        /*
         * Close stderr and open /dev/tty.   See what it's flags
         * are.   Set the file to non blocking.
         */
        printf("close stderr and open /dev/tty\n");
        assert(close(STDERR_FILENO) != -1);
        new_fd = open("/dev/tty", O_RDWR|O_CREAT, 0666);
        assert(new_fd == STDERR_FILENO);
        new_flags = fcntl(STDERR_FILENO, F_GETFL);
        assert(new_flags != -1);
        printf("/dev/tty [STDERR_FILENO] flags are %x\n", new_flags);
        stderr_flags = new_flags | O_NONBLOCK;
        printf("forcing /dev/tty to O_NONBLOCK (flags %x)\n", stderr_flags);
        assert(fcntl(STDERR_FILENO, F_SETFL, stdin_flags) != -1);

        /* now turn off non blocking mode on stdin */
        stdin_flags &= ~O_NONBLOCK;
        printf("turning off O_NONBLOCK on stdin (flags %x)\n", stdin_flags);
        assert(fcntl(STDIN_FILENO, F_SETFL, stdin_flags) != -1);

        new_flags = fcntl(STDIN_FILENO, F_GETFL);
        assert(new_flags != -1);
        assert(new_flags == stdin_flags);

        new_flags = fcntl(STDOUT_FILENO, F_GETFL);
        assert(new_flags != -1);
        if (new_flags != stdout_flags) {
                printf("stdout flags changed %x -> %x\n", stdout_flags,
                       new_flags);
                stdout_flags = new_flags;
        }

        new_flags = fcntl(dup_stdout, F_GETFL);
        assert(new_flags != -1);
        if (new_flags != dup_flags) {
                printf("dup_stdout flags changed %x -> %x\n", dup_flags,
                       new_flags);
                dup_flags = new_flags;
        }

        new_flags = fcntl(STDERR_FILENO, F_GETFL);
        assert(new_flags != -1);
        if (new_flags != stderr_flags) {
                printf("stderr flags changed %x -> %x\n", stderr_flags,
                       new_flags);
                stderr_flags = new_flags;
        }

        return 0;
}