shared: add terminal-util.[ch]

1 files changed, 1072 insertions, 0 deletions

diff --git a/src/shared/terminal-util.c b/src/shared/terminal-util.c
new file mode 100644
index 0000000000..f5b6590993
--- /dev/null
+++ b/src/shared/terminal-util.c
@@ -0,0 +1,1072 @@
+/***
+  This file is part of systemd.
+
+  Copyright 2010 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <sys/ioctl.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <termios.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <time.h>
+#include <assert.h>
+#include <poll.h>
+#include <linux/vt.h>
+#include <linux/tiocl.h>
+#include <linux/kd.h>
+
+#include "terminal-util.h"
+#include "time-util.h"
+#include "process-util.h"
+#include "util.h"
+#include "fileio.h"
+#include "path-util.h"
+
+static volatile unsigned cached_columns = 0;
+static volatile unsigned cached_lines = 0;
+
+int chvt(int vt) {
+        _cleanup_close_ int fd;
+
+        fd = open_terminal("/dev/tty0", O_RDWR|O_NOCTTY|O_CLOEXEC);
+        if (fd < 0)
+                return -errno;
+
+        if (vt < 0) {
+                int tiocl[2] = {
+                        TIOCL_GETKMSGREDIRECT,
+                        0
+                };
+
+                if (ioctl(fd, TIOCLINUX, tiocl) < 0)
+                        return -errno;
+
+                vt = tiocl[0] <= 0 ? 1 : tiocl[0];
+        }
+
+        if (ioctl(fd, VT_ACTIVATE, vt) < 0)
+                return -errno;
+
+        return 0;
+}
+
+int read_one_char(FILE *f, char *ret, usec_t t, bool *need_nl) {
+        struct termios old_termios, new_termios;
+        char c, line[LINE_MAX];
+
+        assert(f);
+        assert(ret);
+
+        if (tcgetattr(fileno(f), &old_termios) >= 0) {
+                new_termios = old_termios;
+
+                new_termios.c_lflag &= ~ICANON;
+                new_termios.c_cc[VMIN] = 1;
+                new_termios.c_cc[VTIME] = 0;
+
+                if (tcsetattr(fileno(f), TCSADRAIN, &new_termios) >= 0) {
+                        size_t k;
+
+                        if (t != USEC_INFINITY) {
+                                if (fd_wait_for_event(fileno(f), POLLIN, t) <= 0) {
+                                        tcsetattr(fileno(f), TCSADRAIN, &old_termios);
+                                        return -ETIMEDOUT;
+                                }
+                        }
+
+                        k = fread(&c, 1, 1, f);
+
+                        tcsetattr(fileno(f), TCSADRAIN, &old_termios);
+
+                        if (k <= 0)
+                                return -EIO;
+
+                        if (need_nl)
+                                *need_nl = c != '\n';
+
+                        *ret = c;
+                        return 0;
+                }
+        }
+
+        if (t != USEC_INFINITY) {
+                if (fd_wait_for_event(fileno(f), POLLIN, t) <= 0)
+                        return -ETIMEDOUT;
+        }
+
+        errno = 0;
+        if (!fgets(line, sizeof(line), f))
+                return errno ? -errno : -EIO;
+
+        truncate_nl(line);
+
+        if (strlen(line) != 1)
+                return -EBADMSG;
+
+        if (need_nl)
+                *need_nl = false;
+
+        *ret = line[0];
+        return 0;
+}
+
+int ask_char(char *ret, const char *replies, const char *text, ...) {
+        int r;
+
+        assert(ret);
+        assert(replies);
+        assert(text);
+
+        for (;;) {
+                va_list ap;
+                char c;
+                bool need_nl = true;
+
+                if (on_tty())
+                        fputs(ANSI_HIGHLIGHT_ON, stdout);
+
+                va_start(ap, text);
+                vprintf(text, ap);
+                va_end(ap);
+
+                if (on_tty())
+                        fputs(ANSI_HIGHLIGHT_OFF, stdout);
+
+                fflush(stdout);
+
+                r = read_one_char(stdin, &c, USEC_INFINITY, &need_nl);
+                if (r < 0) {
+
+                        if (r == -EBADMSG) {
+                                puts("Bad input, please try again.");
+                                continue;
+                        }
+
+                        putchar('\n');
+                        return r;
+                }
+
+                if (need_nl)
+                        putchar('\n');
+
+                if (strchr(replies, c)) {
+                        *ret = c;
+                        return 0;
+                }
+
+                puts("Read unexpected character, please try again.");
+        }
+}
+
+int ask_string(char **ret, const char *text, ...) {
+        assert(ret);
+        assert(text);
+
+        for (;;) {
+                char line[LINE_MAX];
+                va_list ap;
+
+                if (on_tty())
+                        fputs(ANSI_HIGHLIGHT_ON, stdout);
+
+                va_start(ap, text);
+                vprintf(text, ap);
+                va_end(ap);
+
+                if (on_tty())
+                        fputs(ANSI_HIGHLIGHT_OFF, stdout);
+
+                fflush(stdout);
+
+                errno = 0;
+                if (!fgets(line, sizeof(line), stdin))
+                        return errno ? -errno : -EIO;
+
+                if (!endswith(line, "\n"))
+                        putchar('\n');
+                else {
+                        char *s;
+
+                        if (isempty(line))
+                                continue;
+
+                        truncate_nl(line);
+                        s = strdup(line);
+                        if (!s)
+                                return -ENOMEM;
+
+                        *ret = s;
+                        return 0;
+                }
+        }
+}
+
+int reset_terminal_fd(int fd, bool switch_to_text) {
+        struct termios termios;
+        int r = 0;
+
+        /* Set terminal to some sane defaults */
+
+        assert(fd >= 0);
+
+        /* We leave locked terminal attributes untouched, so that
+         * Plymouth may set whatever it wants to set, and we don't
+         * interfere with that. */
+
+        /* Disable exclusive mode, just in case */
+        ioctl(fd, TIOCNXCL);
+
+        /* Switch to text mode */
+        if (switch_to_text)
+                ioctl(fd, KDSETMODE, KD_TEXT);
+
+        /* Enable console unicode mode */
+        ioctl(fd, KDSKBMODE, K_UNICODE);
+
+        if (tcgetattr(fd, &termios) < 0) {
+                r = -errno;
+                goto finish;
+        }
+
+        /* We only reset the stuff that matters to the software. How
+         * hardware is set up we don't touch assuming that somebody
+         * else will do that for us */
+
+        termios.c_iflag &= ~(IGNBRK | BRKINT | ISTRIP | INLCR | IGNCR | IUCLC);
+        termios.c_iflag |= ICRNL | IMAXBEL | IUTF8;
+        termios.c_oflag |= ONLCR;
+        termios.c_cflag |= CREAD;
+        termios.c_lflag = ISIG | ICANON | IEXTEN | ECHO | ECHOE | ECHOK | ECHOCTL | ECHOPRT | ECHOKE;
+
+        termios.c_cc[VINTR]    =   03;  /* ^C */
+        termios.c_cc[VQUIT]    =  034;  /* ^\ */
+        termios.c_cc[VERASE]   = 0177;
+        termios.c_cc[VKILL]    =  025;  /* ^X */
+        termios.c_cc[VEOF]     =   04;  /* ^D */
+        termios.c_cc[VSTART]   =  021;  /* ^Q */
+        termios.c_cc[VSTOP]    =  023;  /* ^S */
+        termios.c_cc[VSUSP]    =  032;  /* ^Z */
+        termios.c_cc[VLNEXT]   =  026;  /* ^V */
+        termios.c_cc[VWERASE]  =  027;  /* ^W */
+        termios.c_cc[VREPRINT] =  022;  /* ^R */
+        termios.c_cc[VEOL]     =    0;
+        termios.c_cc[VEOL2]    =    0;
+
+        termios.c_cc[VTIME]  = 0;
+        termios.c_cc[VMIN]   = 1;
+
+        if (tcsetattr(fd, TCSANOW, &termios) < 0)
+                r = -errno;
+
+finish:
+        /* Just in case, flush all crap out */
+        tcflush(fd, TCIOFLUSH);
+
+        return r;
+}
+
+int reset_terminal(const char *name) {
+        _cleanup_close_ int fd = -1;
+
+        fd = open_terminal(name, O_RDWR|O_NOCTTY|O_CLOEXEC);
+        if (fd < 0)
+                return fd;
+
+        return reset_terminal_fd(fd, true);
+}
+
+int open_terminal(const char *name, int mode) {
+        int fd, r;
+        unsigned c = 0;
+
+        /*
+         * If a TTY is in the process of being closed opening it might
+         * cause EIO. This is horribly awful, but unlikely to be
+         * changed in the kernel. Hence we work around this problem by
+         * retrying a couple of times.
+         *
+         * https://bugs.launchpad.net/ubuntu/+source/linux/+bug/554172/comments/245
+         */
+
+        assert(!(mode & O_CREAT));
+
+        for (;;) {
+                fd = open(name, mode, 0);
+                if (fd >= 0)
+                        break;
+
+                if (errno != EIO)
+                        return -errno;
+
+                /* Max 1s in total */
+                if (c >= 20)
+                        return -errno;
+
+                usleep(50 * USEC_PER_MSEC);
+                c++;
+        }
+
+        r = isatty(fd);
+        if (r < 0) {
+                safe_close(fd);
+                return -errno;
+        }
+
+        if (!r) {
+                safe_close(fd);
+                return -ENOTTY;
+        }
+
+        return fd;
+}
+
+int acquire_terminal(
+                const char *name,
+                bool fail,
+                bool force,
+                bool ignore_tiocstty_eperm,
+                usec_t timeout) {
+
+        int fd = -1, notify = -1, r = 0, wd = -1;
+        usec_t ts = 0;
+
+        assert(name);
+
+        /* We use inotify to be notified when the tty is closed. We
+         * create the watch before checking if we can actually acquire
+         * it, so that we don't lose any event.
+         *
+         * Note: strictly speaking this actually watches for the
+         * device being closed, it does *not* really watch whether a
+         * tty loses its controlling process. However, unless some
+         * rogue process uses TIOCNOTTY on /dev/tty *after* closing
+         * its tty otherwise this will not become a problem. As long
+         * as the administrator makes sure not configure any service
+         * on the same tty as an untrusted user this should not be a
+         * problem. (Which he probably should not do anyway.) */
+
+        if (timeout != USEC_INFINITY)
+                ts = now(CLOCK_MONOTONIC);
+
+        if (!fail && !force) {
+                notify = inotify_init1(IN_CLOEXEC | (timeout != USEC_INFINITY ? IN_NONBLOCK : 0));
+                if (notify < 0) {
+                        r = -errno;
+                        goto fail;
+                }
+
+                wd = inotify_add_watch(notify, name, IN_CLOSE);
+                if (wd < 0) {
+                        r = -errno;
+                        goto fail;
+                }
+        }
+
+        for (;;) {
+                struct sigaction sa_old, sa_new = {
+                        .sa_handler = SIG_IGN,
+                        .sa_flags = SA_RESTART,
+                };
+
+                if (notify >= 0) {
+                        r = flush_fd(notify);
+                        if (r < 0)
+                                goto fail;
+                }
+
+                /* We pass here O_NOCTTY only so that we can check the return
+                 * value TIOCSCTTY and have a reliable way to figure out if we
+                 * successfully became the controlling process of the tty */
+                fd = open_terminal(name, O_RDWR|O_NOCTTY|O_CLOEXEC);
+                if (fd < 0)
+                        return fd;
+
+                /* Temporarily ignore SIGHUP, so that we don't get SIGHUP'ed
+                 * if we already own the tty. */
+                assert_se(sigaction(SIGHUP, &sa_new, &sa_old) == 0);
+
+                /* First, try to get the tty */
+                if (ioctl(fd, TIOCSCTTY, force) < 0)
+                        r = -errno;
+
+                assert_se(sigaction(SIGHUP, &sa_old, NULL) == 0);
+
+                /* Sometimes it makes sense to ignore TIOCSCTTY
+                 * returning EPERM, i.e. when very likely we already
+                 * are have this controlling terminal. */
+                if (r < 0 && r == -EPERM && ignore_tiocstty_eperm)
+                        r = 0;
+
+                if (r < 0 && (force || fail || r != -EPERM)) {
+                        goto fail;
+                }
+
+                if (r >= 0)
+                        break;
+
+                assert(!fail);
+                assert(!force);
+                assert(notify >= 0);
+
+                for (;;) {
+                        union inotify_event_buffer buffer;
+                        struct inotify_event *e;
+                        ssize_t l;
+
+                        if (timeout != USEC_INFINITY) {
+                                usec_t n;
+
+                                n = now(CLOCK_MONOTONIC);
+                                if (ts + timeout < n) {
+                                        r = -ETIMEDOUT;
+                                        goto fail;
+                                }
+
+                                r = fd_wait_for_event(fd, POLLIN, ts + timeout - n);
+                                if (r < 0)
+                                        goto fail;
+
+                                if (r == 0) {
+                                        r = -ETIMEDOUT;
+                                        goto fail;
+                                }
+                        }
+
+                        l = read(notify, &buffer, sizeof(buffer));
+                        if (l < 0) {
+                                if (errno == EINTR || errno == EAGAIN)
+                                        continue;
+
+                                r = -errno;
+                                goto fail;
+                        }
+
+                        FOREACH_INOTIFY_EVENT(e, buffer, l) {
+                                if (e->wd != wd || !(e->mask & IN_CLOSE)) {
+                                        r = -EIO;
+                                        goto fail;
+                                }
+                        }
+
+                        break;
+                }
+
+                /* We close the tty fd here since if the old session
+                 * ended our handle will be dead. It's important that
+                 * we do this after sleeping, so that we don't enter
+                 * an endless loop. */
+                fd = safe_close(fd);
+        }
+
+        safe_close(notify);
+
+        r = reset_terminal_fd(fd, true);
+        if (r < 0)
+                log_warning_errno(r, "Failed to reset terminal: %m");
+
+        return fd;
+
+fail:
+        safe_close(fd);
+        safe_close(notify);
+
+        return r;
+}
+
+int release_terminal(void) {
+        static const struct sigaction sa_new = {
+                .sa_handler = SIG_IGN,
+                .sa_flags = SA_RESTART,
+        };
+
+        _cleanup_close_ int fd = -1;
+        struct sigaction sa_old;
+        int r = 0;
+
+        fd = open("/dev/tty", O_RDWR|O_NOCTTY|O_NDELAY|O_CLOEXEC);
+        if (fd < 0)
+                return -errno;
+
+        /* Temporarily ignore SIGHUP, so that we don't get SIGHUP'ed
+         * by our own TIOCNOTTY */
+        assert_se(sigaction(SIGHUP, &sa_new, &sa_old) == 0);
+
+        if (ioctl(fd, TIOCNOTTY) < 0)
+                r = -errno;
+
+        assert_se(sigaction(SIGHUP, &sa_old, NULL) == 0);
+
+        return r;
+}
+
+int terminal_vhangup_fd(int fd) {
+        assert(fd >= 0);
+
+        if (ioctl(fd, TIOCVHANGUP) < 0)
+                return -errno;
+
+        return 0;
+}
+
+int terminal_vhangup(const char *name) {
+        _cleanup_close_ int fd;
+
+        fd = open_terminal(name, O_RDWR|O_NOCTTY|O_CLOEXEC);
+        if (fd < 0)
+                return fd;
+
+        return terminal_vhangup_fd(fd);
+}
+
+int vt_disallocate(const char *name) {
+        int fd, r;
+        unsigned u;
+
+        /* Deallocate the VT if possible. If not possible
+         * (i.e. because it is the active one), at least clear it
+         * entirely (including the scrollback buffer) */
+
+        if (!startswith(name, "/dev/"))
+                return -EINVAL;
+
+        if (!tty_is_vc(name)) {
+                /* So this is not a VT. I guess we cannot deallocate
+                 * it then. But let's at least clear the screen */
+
+                fd = open_terminal(name, O_RDWR|O_NOCTTY|O_CLOEXEC);
+                if (fd < 0)
+                        return fd;
+
+                loop_write(fd,
+                           "\033[r"    /* clear scrolling region */
+                           "\033[H"    /* move home */
+                           "\033[2J",  /* clear screen */
+                           10, false);
+                safe_close(fd);
+
+                return 0;
+        }
+
+        if (!startswith(name, "/dev/tty"))
+                return -EINVAL;
+
+        r = safe_atou(name+8, &u);
+        if (r < 0)
+                return r;
+
+        if (u <= 0)
+                return -EINVAL;
+
+        /* Try to deallocate */
+        fd = open_terminal("/dev/tty0", O_RDWR|O_NOCTTY|O_CLOEXEC);
+        if (fd < 0)
+                return fd;
+
+        r = ioctl(fd, VT_DISALLOCATE, u);
+        safe_close(fd);
+
+        if (r >= 0)
+                return 0;
+
+        if (errno != EBUSY)
+                return -errno;
+
+        /* Couldn't deallocate, so let's clear it fully with
+         * scrollback */
+        fd = open_terminal(name, O_RDWR|O_NOCTTY|O_CLOEXEC);
+        if (fd < 0)
+                return fd;
+
+        loop_write(fd,
+                   "\033[r"   /* clear scrolling region */
+                   "\033[H"   /* move home */
+                   "\033[3J", /* clear screen including scrollback, requires Linux 2.6.40 */
+                   10, false);
+        safe_close(fd);
+
+        return 0;
+}
+
+void warn_melody(void) {
+        _cleanup_close_ int fd = -1;
+
+        fd = open("/dev/console", O_WRONLY|O_CLOEXEC|O_NOCTTY);
+        if (fd < 0)
+                return;
+
+        /* Yeah, this is synchronous. Kinda sucks. But well... */
+
+        ioctl(fd, KIOCSOUND, (int)(1193180/440));
+        usleep(125*USEC_PER_MSEC);
+
+        ioctl(fd, KIOCSOUND, (int)(1193180/220));
+        usleep(125*USEC_PER_MSEC);
+
+        ioctl(fd, KIOCSOUND, (int)(1193180/220));
+        usleep(125*USEC_PER_MSEC);
+
+        ioctl(fd, KIOCSOUND, 0);
+}
+
+int make_console_stdio(void) {
+        int fd, r;
+
+        /* Make /dev/console the controlling terminal and stdin/stdout/stderr */
+
+        fd = acquire_terminal("/dev/console", false, true, true, USEC_INFINITY);
+        if (fd < 0)
+                return log_error_errno(fd, "Failed to acquire terminal: %m");
+
+        r = make_stdio(fd);
+        if (r < 0)
+                return log_error_errno(r, "Failed to duplicate terminal fd: %m");
+
+        return 0;
+}
+
+int status_vprintf(const char *status, bool ellipse, bool ephemeral, const char *format, va_list ap) {
+        static const char status_indent[] = "         "; /* "[" STATUS "] " */
+        _cleanup_free_ char *s = NULL;
+        _cleanup_close_ int fd = -1;
+        struct iovec iovec[6] = {};
+        int n = 0;
+        static bool prev_ephemeral;
+
+        assert(format);
+
+        /* This is independent of logging, as status messages are
+         * optional and go exclusively to the console. */
+
+        if (vasprintf(&s, format, ap) < 0)
+                return log_oom();
+
+        fd = open_terminal("/dev/console", O_WRONLY|O_NOCTTY|O_CLOEXEC);
+        if (fd < 0)
+                return fd;
+
+        if (ellipse) {
+                char *e;
+                size_t emax, sl;
+                int c;
+
+                c = fd_columns(fd);
+                if (c <= 0)
+                        c = 80;
+
+                sl = status ? sizeof(status_indent)-1 : 0;
+
+                emax = c - sl - 1;
+                if (emax < 3)
+                        emax = 3;
+
+                e = ellipsize(s, emax, 50);
+                if (e) {
+                        free(s);
+                        s = e;
+                }
+        }
+
+        if (prev_ephemeral)
+                IOVEC_SET_STRING(iovec[n++], "\r" ANSI_ERASE_TO_END_OF_LINE);
+        prev_ephemeral = ephemeral;
+
+        if (status) {
+                if (!isempty(status)) {
+                        IOVEC_SET_STRING(iovec[n++], "[");
+                        IOVEC_SET_STRING(iovec[n++], status);
+                        IOVEC_SET_STRING(iovec[n++], "] ");
+                } else
+                        IOVEC_SET_STRING(iovec[n++], status_indent);
+        }
+
+        IOVEC_SET_STRING(iovec[n++], s);
+        if (!ephemeral)
+                IOVEC_SET_STRING(iovec[n++], "\n");
+
+        if (writev(fd, iovec, n) < 0)
+                return -errno;
+
+        return 0;
+}
+
+int status_printf(const char *status, bool ellipse, bool ephemeral, const char *format, ...) {
+        va_list ap;
+        int r;
+
+        assert(format);
+
+        va_start(ap, format);
+        r = status_vprintf(status, ellipse, ephemeral, format, ap);
+        va_end(ap);
+
+        return r;
+}
+
+bool tty_is_vc(const char *tty) {
+        assert(tty);
+
+        return vtnr_from_tty(tty) >= 0;
+}
+
+bool tty_is_console(const char *tty) {
+        assert(tty);
+
+        if (startswith(tty, "/dev/"))
+                tty += 5;
+
+        return streq(tty, "console");
+}
+
+int vtnr_from_tty(const char *tty) {
+        int i, r;
+
+        assert(tty);
+
+        if (startswith(tty, "/dev/"))
+                tty += 5;
+
+        if (!startswith(tty, "tty") )
+                return -EINVAL;
+
+        if (tty[3] < '0' || tty[3] > '9')
+                return -EINVAL;
+
+        r = safe_atoi(tty+3, &i);
+        if (r < 0)
+                return r;
+
+        if (i < 0 || i > 63)
+                return -EINVAL;
+
+        return i;
+}
+
+char *resolve_dev_console(char **active) {
+        char *tty;
+
+        /* Resolve where /dev/console is pointing to, if /sys is actually ours
+         * (i.e. not read-only-mounted which is a sign for container setups) */
+
+        if (path_is_read_only_fs("/sys") > 0)
+                return NULL;
+
+        if (read_one_line_file("/sys/class/tty/console/active", active) < 0)
+                return NULL;
+
+        /* If multiple log outputs are configured the last one is what
+         * /dev/console points to */
+        tty = strrchr(*active, ' ');
+        if (tty)
+                tty++;
+        else
+                tty = *active;
+
+        if (streq(tty, "tty0")) {
+                char *tmp;
+
+                /* Get the active VC (e.g. tty1) */
+                if (read_one_line_file("/sys/class/tty/tty0/active", &tmp) >= 0) {
+                        free(*active);
+                        tty = *active = tmp;
+                }
+        }
+
+        return tty;
+}
+
+bool tty_is_vc_resolve(const char *tty) {
+        _cleanup_free_ char *active = NULL;
+
+        assert(tty);
+
+        if (startswith(tty, "/dev/"))
+                tty += 5;
+
+        if (streq(tty, "console")) {
+                tty = resolve_dev_console(&active);
+                if (!tty)
+                        return false;
+        }
+
+        return tty_is_vc(tty);
+}
+
+const char *default_term_for_tty(const char *tty) {
+        assert(tty);
+
+        return tty_is_vc_resolve(tty) ? "TERM=linux" : "TERM=vt220";
+}
+
+int fd_columns(int fd) {
+        struct winsize ws = {};
+
+        if (ioctl(fd, TIOCGWINSZ, &ws) < 0)
+                return -errno;
+
+        if (ws.ws_col <= 0)
+                return -EIO;
+
+        return ws.ws_col;
+}
+
+unsigned columns(void) {
+        const char *e;
+        int c;
+
+        if (_likely_(cached_columns > 0))
+                return cached_columns;
+
+        c = 0;
+        e = getenv("COLUMNS");
+        if (e)
+                (void) safe_atoi(e, &c);
+
+        if (c <= 0)
+                c = fd_columns(STDOUT_FILENO);
+
+        if (c <= 0)
+                c = 80;
+
+        cached_columns = c;
+        return cached_columns;
+}
+
+int fd_lines(int fd) {
+        struct winsize ws = {};
+
+        if (ioctl(fd, TIOCGWINSZ, &ws) < 0)
+                return -errno;
+
+        if (ws.ws_row <= 0)
+                return -EIO;
+
+        return ws.ws_row;
+}
+
+unsigned lines(void) {
+        const char *e;
+        int l;
+
+        if (_likely_(cached_lines > 0))
+                return cached_lines;
+
+        l = 0;
+        e = getenv("LINES");
+        if (e)
+                (void) safe_atoi(e, &l);
+
+        if (l <= 0)
+                l = fd_lines(STDOUT_FILENO);
+
+        if (l <= 0)
+                l = 24;
+
+        cached_lines = l;
+        return cached_lines;
+}
+
+/* intended to be used as a SIGWINCH sighandler */
+void columns_lines_cache_reset(int signum) {
+        cached_columns = 0;
+        cached_lines = 0;
+}
+
+bool on_tty(void) {
+        static int cached_on_tty = -1;
+
+        if (_unlikely_(cached_on_tty < 0))
+                cached_on_tty = isatty(STDOUT_FILENO) > 0;
+
+        return cached_on_tty;
+}
+
+int make_stdio(int fd) {
+        int r, s, t;
+
+        assert(fd >= 0);
+
+        r = dup2(fd, STDIN_FILENO);
+        s = dup2(fd, STDOUT_FILENO);
+        t = dup2(fd, STDERR_FILENO);
+
+        if (fd >= 3)
+                safe_close(fd);
+
+        if (r < 0 || s < 0 || t < 0)
+                return -errno;
+
+        /* Explicitly unset O_CLOEXEC, since if fd was < 3, then
+         * dup2() was a NOP and the bit hence possibly set. */
+        fd_cloexec(STDIN_FILENO, false);
+        fd_cloexec(STDOUT_FILENO, false);
+        fd_cloexec(STDERR_FILENO, false);
+
+        return 0;
+}
+
+int make_null_stdio(void) {
+        int null_fd;
+
+        null_fd = open("/dev/null", O_RDWR|O_NOCTTY);
+        if (null_fd < 0)
+                return -errno;
+
+        return make_stdio(null_fd);
+}
+
+int getttyname_malloc(int fd, char **ret) {
+        size_t l = 100;
+        int r;
+
+        assert(fd >= 0);
+        assert(ret);
+
+        for (;;) {
+                char path[l];
+
+                r = ttyname_r(fd, path, sizeof(path));
+                if (r == 0) {
+                        const char *p;
+                        char *c;
+
+                        p = startswith(path, "/dev/");
+                        c = strdup(p ?: path);
+                        if (!c)
+                                return -ENOMEM;
+
+                        *ret = c;
+                        return 0;
+                }
+
+                if (r != ERANGE)
+                        return -r;
+
+                l *= 2;
+        }
+
+        return 0;
+}
+
+int getttyname_harder(int fd, char **r) {
+        int k;
+        char *s = NULL;
+
+        k = getttyname_malloc(fd, &s);
+        if (k < 0)
+                return k;
+
+        if (streq(s, "tty")) {
+                free(s);
+                return get_ctty(0, NULL, r);
+        }
+
+        *r = s;
+        return 0;
+}
+
+int get_ctty_devnr(pid_t pid, dev_t *d) {
+        int r;
+        _cleanup_free_ char *line = NULL;
+        const char *p;
+        unsigned long ttynr;
+
+        assert(pid >= 0);
+
+        p = procfs_file_alloca(pid, "stat");
+        r = read_one_line_file(p, &line);
+        if (r < 0)
+                return r;
+
+        p = strrchr(line, ')');
+        if (!p)
+                return -EIO;
+
+        p++;
+
+        if (sscanf(p, " "
+                   "%*c "  /* state */
+                   "%*d "  /* ppid */
+                   "%*d "  /* pgrp */
+                   "%*d "  /* session */
+                   "%lu ", /* ttynr */
+                   &ttynr) != 1)
+                return -EIO;
+
+        if (major(ttynr) == 0 && minor(ttynr) == 0)
+                return -ENOENT;
+
+        if (d)
+                *d = (dev_t) ttynr;
+
+        return 0;
+}
+
+int get_ctty(pid_t pid, dev_t *_devnr, char **r) {
+        char fn[sizeof("/dev/char/")-1 + 2*DECIMAL_STR_MAX(unsigned) + 1 + 1], *b = NULL;
+        _cleanup_free_ char *s = NULL;
+        const char *p;
+        dev_t devnr;
+        int k;
+
+        assert(r);
+
+        k = get_ctty_devnr(pid, &devnr);
+        if (k < 0)
+                return k;
+
+        sprintf(fn, "/dev/char/%u:%u", major(devnr), minor(devnr));
+
+        k = readlink_malloc(fn, &s);
+        if (k < 0) {
+
+                if (k != -ENOENT)
+                        return k;
+
+                /* This is an ugly hack */
+                if (major(devnr) == 136) {
+                        if (asprintf(&b, "pts/%u", minor(devnr)) < 0)
+                                return -ENOMEM;
+                } else {
+                        /* Probably something like the ptys which have no
+                         * symlink in /dev/char. Let's return something
+                         * vaguely useful. */
+
+                        b = strdup(fn + 5);
+                        if (!b)
+                                return -ENOMEM;
+                }
+        } else {
+                if (startswith(s, "/dev/"))
+                        p = s + 5;
+                else if (startswith(s, "../"))
+                        p = s + 3;
+                else
+                        p = s;
+
+                b = strdup(p);
+                if (!b)
+                        return -ENOMEM;
+        }
+
+        *r = b;
+        if (_devnr)
+                *_devnr = devnr;
+
+        return 0;
+}