cgtop: add new cgtop tool

5 files changed, 786 insertions, 9 deletions

diff --git a/src/cgtop.c b/src/cgtop.c
new file mode 100644
index 0000000000..4624bc4af5
--- /dev/null
+++ b/src/cgtop.c
@@ -0,0 +1,729 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2012 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 2 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
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <errno.h>
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <alloca.h>
+#include <getopt.h>
+
+#include "util.h"
+#include "hashmap.h"
+#include "cgroup-util.h"
+
+typedef struct Group {
+        char *path;
+
+        bool n_tasks_valid:1;
+        bool cpu_valid:1;
+        bool memory_valid:1;
+        bool io_valid:1;
+
+        unsigned n_tasks;
+
+        unsigned cpu_iteration;
+        uint64_t cpu_usage;
+        struct timespec cpu_timestamp;
+        double cpu_fraction;
+
+        uint64_t memory;
+
+        unsigned io_iteration;
+        uint64_t io_input, io_output;
+        struct timespec io_timestamp;
+        uint64_t io_input_bps, io_output_bps;
+} Group;
+
+static unsigned arg_depth = 2;
+static usec_t arg_delay = 1*USEC_PER_SEC;
+
+static enum {
+        ORDER_PATH,
+        ORDER_TASKS,
+        ORDER_CPU,
+        ORDER_MEMORY,
+        ORDER_IO
+} arg_order = ORDER_CPU;
+
+static void group_free(Group *g) {
+        assert(g);
+
+        free(g->path);
+        free(g);
+}
+
+static void group_hashmap_clear(Hashmap *h) {
+        Group *g;
+
+        while ((g = hashmap_steal_first(h)))
+                group_free(g);
+}
+
+static void group_hashmap_free(Hashmap *h) {
+        group_hashmap_clear(h);
+        hashmap_free(h);
+}
+
+static int process(const char *controller, const char *path, Hashmap *a, Hashmap *b, unsigned iteration) {
+        Group *g;
+        int r;
+        FILE *f;
+        pid_t pid;
+        unsigned n;
+
+        assert(controller);
+        assert(path);
+        assert(a);
+
+        g = hashmap_get(a, path);
+        if (!g) {
+                g = hashmap_get(b, path);
+                if (!g) {
+                        g = new0(Group, 1);
+                        if (!g)
+                                return -ENOMEM;
+
+                        g->path = strdup(path);
+                        if (!g->path) {
+                                group_free(g);
+                                return -ENOMEM;
+                        }
+
+                        r = hashmap_put(a, g->path, g);
+                        if (r < 0) {
+                                group_free(g);
+                                return r;
+                        }
+                } else {
+                        assert_se(hashmap_move_one(a, b, path) == 0);
+                        g->cpu_valid = g->memory_valid = g->io_valid = g->n_tasks_valid = false;
+                }
+        }
+
+        /* Regardless which controller, let's find the maximum number
+         * of processes in any of it */
+
+        r = cg_enumerate_tasks(controller, path, &f);
+        if (r < 0)
+                return r;
+
+        n = 0;
+        while (cg_read_pid(f, &pid) > 0)
+                n++;
+        fclose(f);
+
+        if (n > 0) {
+                if (g->n_tasks_valid)
+                        g->n_tasks = MAX(g->n_tasks, n);
+                else
+                        g->n_tasks = n;
+
+                g->n_tasks_valid = true;
+        }
+
+        if (streq(controller, "cpuacct")) {
+                uint64_t new_usage;
+                char *p, *v;
+                struct timespec ts;
+
+                r = cg_get_path(controller, path, "cpuacct.usage", &p);
+                if (r < 0)
+                        return r;
+
+                r = read_one_line_file(p, &v);
+                free(p);
+                if (r < 0)
+                        return r;
+
+                r = safe_atou64(v, &new_usage);
+                free(v);
+                if (r < 0)
+                        return r;
+
+                assert_se(clock_gettime(CLOCK_MONOTONIC, &ts) == 0);
+
+                if (g->cpu_iteration == iteration - 1) {
+                        uint64_t x, y;
+
+                        x = ((uint64_t) ts.tv_sec * 1000000000ULL + (uint64_t) ts.tv_nsec) -
+                                ((uint64_t) g->cpu_timestamp.tv_sec * 1000000000ULL + (uint64_t) g->cpu_timestamp.tv_nsec);
+
+                        y = new_usage - g->cpu_usage;
+
+                        if (y > 0) {
+                                g->cpu_fraction = (double) y / (double) x;
+                                g->cpu_valid = true;
+                        }
+                }
+
+                g->cpu_usage = new_usage;
+                g->cpu_timestamp = ts;
+                g->cpu_iteration = iteration;
+
+        } else if (streq(controller, "memory")) {
+                char *p, *v;
+
+                r = cg_get_path(controller, path, "memory.usage_in_bytes", &p);
+                if (r < 0)
+                        return r;
+
+                r = read_one_line_file(p, &v);
+                free(p);
+                if (r < 0)
+                        return r;
+
+                r = safe_atou64(v, &g->memory);
+                free(v);
+                if (r < 0)
+                        return r;
+
+                if (g->memory > 0)
+                        g->memory_valid = true;
+
+        } else if (streq(controller, "blkio")) {
+                char *p;
+                uint64_t wr = 0, rd = 0;
+                struct timespec ts;
+
+                r = cg_get_path(controller, path, "blkio.io_service_bytes", &p);
+                if (r < 0)
+                        return r;
+
+                f = fopen(p, "re");
+                free(p);
+
+                if (!f)
+                        return -errno;
+
+                for (;;) {
+                        char line[LINE_MAX], *l;
+                        uint64_t k, *q;
+
+                        if (!fgets(line, sizeof(line), f))
+                                break;
+
+                        l = strstrip(line);
+                        l += strcspn(l, WHITESPACE);
+                        l += strspn(l, WHITESPACE);
+
+                        if (first_word(l, "Read")) {
+                                l += 4;
+                                q = &rd;
+                        } else if (first_word(l, "Write")) {
+                                l += 5;
+                                q = &wr;
+                        } else
+                                continue;
+
+                        l += strspn(l, WHITESPACE);
+                        r = safe_atou64(l, &k);
+                        if (r < 0)
+                                continue;
+
+                        *q += k;
+                }
+
+                fclose(f);
+
+                assert_se(clock_gettime(CLOCK_MONOTONIC, &ts) == 0);
+
+                if (g->io_iteration == iteration - 1) {
+                        uint64_t x, yr, yw;
+
+                        x = ((uint64_t) ts.tv_sec * 1000000000ULL + (uint64_t) ts.tv_nsec) -
+                                ((uint64_t) g->io_timestamp.tv_sec * 1000000000ULL + (uint64_t) g->io_timestamp.tv_nsec);
+
+                        yr = rd - g->io_input;
+                        yw = wr - g->io_output;
+
+                        if (yr > 0 || yw > 0) {
+                                g->io_input_bps = (yr * 1000000000ULL) / x;
+                                g->io_output_bps = (yw * 1000000000ULL) / x;
+                                g->io_valid = true;
+
+                        }
+                }
+
+                g->io_input = rd;
+                g->io_output = wr;
+                g->io_timestamp = ts;
+                g->io_iteration = iteration;
+        }
+
+        return 0;
+}
+
+static int refresh_one(
+                const char *controller,
+                const char *path,
+                Hashmap *a,
+                Hashmap *b,
+                unsigned iteration,
+                unsigned depth) {
+
+        DIR *d = NULL;
+        int r;
+
+        assert(controller);
+        assert(path);
+        assert(a);
+
+        if (depth > arg_depth)
+                return 0;
+
+        r = process(controller, path, a, b, iteration);
+        if (r < 0)
+                return r;
+
+        r = cg_enumerate_subgroups(controller, path, &d);
+        if (r < 0) {
+                if (r == ENOENT)
+                        return 0;
+
+                return r;
+        }
+
+        for (;;) {
+                char *fn, *p;
+
+                r = cg_read_subgroup(d, &fn);
+                if (r <= 0)
+                        goto finish;
+
+                p = join(path, "/", fn, NULL);
+                free(fn);
+
+                if (!p) {
+                        r = -ENOMEM;
+                        goto finish;
+                }
+
+                path_kill_slashes(p);
+
+                r = refresh_one(controller, p, a, b, iteration, depth + 1);
+                free(p);
+
+                if (r < 0)
+                        goto finish;
+        }
+
+finish:
+        if (d)
+                closedir(d);
+
+        return r;
+}
+
+static int refresh(Hashmap *a, Hashmap *b, unsigned iteration) {
+        int r;
+
+        assert(a);
+
+        r = refresh_one("name=systemd", "/", a, b, iteration, 0);
+        if (r < 0)
+                return r;
+
+        r = refresh_one("cpuacct", "/", a, b, iteration, 0);
+        if (r < 0)
+                return r;
+
+        r = refresh_one("memory", "/", a, b, iteration, 0);
+        if (r < 0)
+                return r;
+
+        return refresh_one("blkio", "/", a, b, iteration, 0);
+}
+
+static int group_compare(const void*a, const void *b) {
+        const Group *x = *(Group**)a, *y = *(Group**)b;
+
+        if (path_startswith(y->path, x->path))
+                return -1;
+        if (path_startswith(x->path, y->path))
+                return 1;
+
+        if (arg_order == ORDER_CPU) {
+                if (x->cpu_valid && y->cpu_valid) {
+
+                        if (x->cpu_fraction > y->cpu_fraction)
+                                return -1;
+                        else if (x->cpu_fraction < y->cpu_fraction)
+                                return 1;
+                } else if (x->cpu_valid)
+                        return -1;
+                else if (y->cpu_valid)
+                        return 1;
+        }
+
+        if (arg_order == ORDER_TASKS) {
+
+                if (x->n_tasks_valid && y->n_tasks_valid) {
+                        if (x->n_tasks > y->n_tasks)
+                                return -1;
+                        else if (x->n_tasks < y->n_tasks)
+                                return 1;
+                } else if (x->n_tasks_valid)
+                        return -1;
+                else if (y->n_tasks_valid)
+                        return 1;
+        }
+
+        if (arg_order == ORDER_MEMORY) {
+                if (x->memory_valid && y->memory_valid) {
+                        if (x->memory > y->memory)
+                                return -1;
+                        else if (x->memory < y->memory)
+                                return 1;
+                } else if (x->memory_valid)
+                        return -1;
+                else if (y->memory_valid)
+                        return 1;
+        }
+
+        if (arg_order == ORDER_IO) {
+                if (x->io_valid && y->io_valid) {
+                        if (x->io_input_bps + x->io_output_bps > y->io_input_bps + y->io_output_bps)
+                                return -1;
+                        else if (x->io_input_bps + x->io_output_bps < y->io_input_bps + y->io_output_bps)
+                                return 1;
+                } else if (x->io_valid)
+                        return -1;
+                else if (y->io_valid)
+                        return 1;
+        }
+
+        return strcmp(x->path, y->path);
+}
+
+static int display(Hashmap *a) {
+        Iterator i;
+        Group *g;
+        Group **array;
+        unsigned rows, n = 0, j;
+
+        assert(a);
+
+        /* Set cursor to top left corner and clear screen */
+        fputs("\033[H"
+              "\033[2J", stdout);
+
+        array = alloca(sizeof(Group*) * hashmap_size(a));
+
+        HASHMAP_FOREACH(g, a, i)
+                if (g->n_tasks_valid || g->cpu_valid || g->memory_valid || g->io_valid)
+                        array[n++] = g;
+
+        qsort(array, n, sizeof(Group*), group_compare);
+
+        rows = fd_lines(STDOUT_FILENO);
+        if (rows <= 0)
+                rows = 25;
+
+        printf("%s%-37s%s %s%7s%s %s%6s%s %s%8s%s %s%8s%s %s%8s%s\n\n",
+               arg_order == ORDER_PATH   ? ANSI_HIGHLIGHT_ON : "", "Path",     arg_order == ORDER_PATH   ? ANSI_HIGHLIGHT_OFF : "",
+               arg_order == ORDER_TASKS  ? ANSI_HIGHLIGHT_ON : "", "Tasks",    arg_order == ORDER_TASKS  ? ANSI_HIGHLIGHT_OFF : "",
+               arg_order == ORDER_CPU    ? ANSI_HIGHLIGHT_ON : "", "%CPU",     arg_order == ORDER_CPU    ? ANSI_HIGHLIGHT_OFF : "",
+               arg_order == ORDER_MEMORY ? ANSI_HIGHLIGHT_ON : "", "Memory",   arg_order == ORDER_MEMORY ? ANSI_HIGHLIGHT_OFF : "",
+               arg_order == ORDER_IO     ? ANSI_HIGHLIGHT_ON : "", "Input/s",  arg_order == ORDER_IO     ? ANSI_HIGHLIGHT_OFF : "",
+               arg_order == ORDER_IO     ? ANSI_HIGHLIGHT_ON : "", "Output/s", arg_order == ORDER_IO     ? ANSI_HIGHLIGHT_OFF : "");
+
+        for (j = 0; j < n; j++) {
+                char *p;
+                char m[FORMAT_BYTES_MAX];
+
+                if (j + 5 > rows)
+                        break;
+
+                g = array[j];
+
+                p = ellipsize(g->path, 37, 33);
+                printf("%-37s", p ? p : g->path);
+                free(p);
+
+                if (g->n_tasks_valid)
+                        printf(" %7u", g->n_tasks);
+                else
+                        fputs("       -", stdout);
+
+                if (g->cpu_valid)
+                        printf(" %6.1f", g->cpu_fraction*100);
+                else
+                        fputs("      -", stdout);
+
+                if (g->memory_valid)
+                        printf(" %8s", format_bytes(m, sizeof(m), g->memory));
+                else
+                        fputs("        -", stdout);
+
+                if (g->io_valid) {
+                        printf(" %8s",
+                               format_bytes(m, sizeof(m), g->io_input_bps));
+                        printf(" %8s",
+                               format_bytes(m, sizeof(m), g->io_output_bps));
+                } else
+                        fputs("        -        -", stdout);
+
+                putchar('\n');
+        }
+
+        return 0;
+}
+
+static void help(void) {
+
+        printf("%s [OPTIONS...]\n\n"
+               "Show top control groups by their resource usage.\n\n"
+               "  -h --help           Show this help\n"
+               "  -p                  Order by path\n"
+               "  -t                  Order by number of tasks\n"
+               "  -c                  Order by CPU load\n"
+               "  -m                  Order by memory load\n"
+               "  -i                  Order by IO load\n"
+               "  -d --delay=DELAY    Specify delay\n"
+               "     --depth=DEPTH    Maximum traversal depth\n",
+               program_invocation_short_name);
+}
+
+static int parse_argv(int argc, char *argv[]) {
+
+        enum {
+                ARG_DEPTH = 0x100
+        };
+
+        static const struct option options[] = {
+                { "help",  no_argument,       NULL, 'h'       },
+                { "delay", required_argument, NULL, 'd'       },
+                { "depth", required_argument, NULL, ARG_DEPTH },
+                { NULL,    0,                 NULL, 0         }
+        };
+
+        int c;
+        int r;
+
+        assert(argc >= 1);
+        assert(argv);
+
+        while ((c = getopt_long(argc, argv, "hptcmid:", options, NULL)) >= 0) {
+
+                switch (c) {
+
+                case 'h':
+                        help();
+                        return 0;
+
+                case ARG_DEPTH:
+                        r = safe_atou(optarg, &arg_depth);
+                        if (r < 0) {
+                                log_error("Failed to parse depth parameter.");
+                                return -EINVAL;
+                        }
+
+                        break;
+
+                case 'd':
+                        r = parse_usec(optarg, &arg_delay);
+                        if (r < 0 || arg_delay <= 0) {
+                                log_error("Failed to parse delay parameter.");
+                                return -EINVAL;
+                        }
+
+                        break;
+
+                case 'p':
+                        arg_order = ORDER_PATH;
+                        break;
+
+                case 't':
+                        arg_order = ORDER_TASKS;
+                        break;
+
+                case 'c':
+                        arg_order = ORDER_CPU;
+                        break;
+
+                case 'm':
+                        arg_order = ORDER_MEMORY;
+                        break;
+
+                case 'i':
+                        arg_order = ORDER_IO;
+                        break;
+
+                case '?':
+                        return -EINVAL;
+
+                default:
+                        log_error("Unknown option code %c", c);
+                        return -EINVAL;
+                }
+        }
+
+        if (optind < argc) {
+                log_error("Too many arguments.");
+                return -EINVAL;
+        }
+
+        return 1;
+}
+
+int main(int argc, char *argv[]) {
+        int r;
+        Hashmap *a = NULL, *b = NULL;
+        unsigned iteration = 0;
+        usec_t last_refresh = 0;
+        bool quit = false, immediate_refresh = false;
+
+        log_parse_environment();
+        log_open();
+
+        r = parse_argv(argc, argv);
+        if (r <= 0)
+                goto finish;
+
+        a = hashmap_new(string_hash_func, string_compare_func);
+        b = hashmap_new(string_hash_func, string_compare_func);
+        if (!a || !b) {
+                log_error("Out of memory");
+                r = -ENOMEM;
+                goto finish;
+        }
+
+        while (!quit) {
+                Hashmap *c;
+                usec_t t;
+                char key;
+                char h[FORMAT_TIMESPAN_MAX];
+
+                t = now(CLOCK_MONOTONIC);
+
+                if (t >= last_refresh + arg_delay || immediate_refresh) {
+
+                        r = refresh(a, b, iteration++);
+                        if (r < 0)
+                                goto finish;
+
+                        group_hashmap_clear(b);
+
+                        c = a;
+                        a = b;
+                        b = c;
+
+                        last_refresh = t;
+                        immediate_refresh = false;
+                }
+
+                r = display(b);
+                if (r < 0)
+                        goto finish;
+
+                r = read_one_char(stdin, &key, last_refresh + arg_delay - t, NULL);
+                if (r == -ETIMEDOUT)
+                        continue;
+                if (r < 0) {
+                        log_error("Couldn't read key: %s", strerror(-r));
+                        goto finish;
+                }
+
+                fputs("\r \r", stdout);
+                fflush(stdout);
+
+                switch (key) {
+
+                case ' ':
+                        immediate_refresh = true;
+                        break;
+
+                case 'q':
+                        quit = true;
+                        break;
+
+                case 'p':
+                        arg_order = ORDER_PATH;
+                        break;
+
+                case 't':
+                        arg_order = ORDER_TASKS;
+                        break;
+
+                case 'c':
+                        arg_order = ORDER_CPU;
+                        break;
+
+                case 'm':
+                        arg_order = ORDER_MEMORY;
+                        break;
+
+                case 'i':
+                        arg_order = ORDER_IO;
+                        break;
+
+                case '+':
+                        if (arg_delay < USEC_PER_SEC)
+                                arg_delay += USEC_PER_MSEC*250;
+                        else
+                                arg_delay += USEC_PER_SEC;
+
+                        fprintf(stdout, "\nIncreased delay to %s.", format_timespan(h, sizeof(h), arg_delay));
+                        fflush(stdout);
+                        sleep(1);
+                        break;
+
+                case '-':
+                        if (arg_delay <= USEC_PER_MSEC*500)
+                                arg_delay = USEC_PER_MSEC*250;
+                        else if (arg_delay < USEC_PER_MSEC*1250)
+                                arg_delay -= USEC_PER_MSEC*250;
+                        else
+                                arg_delay -= USEC_PER_SEC;
+
+                        fprintf(stdout, "\nDecreased delay to %s.", format_timespan(h, sizeof(h), arg_delay));
+                        fflush(stdout);
+                        sleep(1);
+                        break;
+
+                case '?':
+                case 'h':
+                        fprintf(stdout,
+                                "\t<" ANSI_HIGHLIGHT_ON "P" ANSI_HIGHLIGHT_OFF "> By path; <" ANSI_HIGHLIGHT_ON "T" ANSI_HIGHLIGHT_OFF "> By tasks; <" ANSI_HIGHLIGHT_ON "C" ANSI_HIGHLIGHT_OFF "> By CPU; <" ANSI_HIGHLIGHT_ON "M" ANSI_HIGHLIGHT_OFF "> By memory; <" ANSI_HIGHLIGHT_ON "I" ANSI_HIGHLIGHT_OFF "> By I/O\n"
+                                "\t<" ANSI_HIGHLIGHT_ON "Q" ANSI_HIGHLIGHT_OFF "> Quit; <" ANSI_HIGHLIGHT_ON "+" ANSI_HIGHLIGHT_OFF "> Increase delay; <" ANSI_HIGHLIGHT_ON "-" ANSI_HIGHLIGHT_OFF "> Decrease delay; <" ANSI_HIGHLIGHT_ON "SPACE" ANSI_HIGHLIGHT_OFF "> Refresh");
+                        fflush(stdout);
+                        sleep(3);
+                        break;
+
+                default:
+                        fprintf(stdout, "\nUnknown key '%c'. Ignoring.", key);
+                        fflush(stdout);
+                        sleep(1);
+                        break;
+                }
+        }
+
+        log_info("Exiting.");
+
+        r = 0;
+
+finish:
+        group_hashmap_free(a);
+        group_hashmap_free(b);
+
+        return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
+}
diff --git a/src/journal/journalctl.c b/src/journal/journalctl.c
index 52db7a9365..8db3fc9201 100644
--- a/src/journal/journalctl.c
+++ b/src/journal/journalctl.c
@@ -282,7 +282,7 @@ int main(int argc, char *argv[]) {
                 if (!arg_follow)
                         break;
 
-                r = fd_wait_for_event(fd, POLLIN);
+                r = fd_wait_for_event(fd, POLLIN, (usec_t) -1);
                 if (r < 0) {
                         log_error("Couldn't wait for event: %s", strerror(-r));
                         goto finish;
diff --git a/src/logs-show.c b/src/logs-show.c
index 5a00133140..f023f0aaef 100644
--- a/src/logs-show.c
+++ b/src/logs-show.c
@@ -633,7 +633,7 @@ int show_journal_by_unit(
                 if (!follow)
                         break;
 
-                r = fd_wait_for_event(fd, POLLIN);
+                r = fd_wait_for_event(fd, POLLIN, (usec_t) -1);
                 if (r < 0)
                         goto finish;
 
diff --git a/src/util.c b/src/util.c
index ef6eea4b9f..1babb6aed4 100644
--- a/src/util.c
+++ b/src/util.c
@@ -2434,7 +2434,7 @@ fail:
         return r;
 }
 
-int read_one_char(FILE *f, char *ret, bool *need_nl) {
+int read_one_char(FILE *f, char *ret, usec_t t, bool *need_nl) {
         struct termios old_termios, new_termios;
         char c;
         char line[LINE_MAX];
@@ -2452,6 +2452,13 @@ int read_one_char(FILE *f, char *ret, bool *need_nl) {
                 if (tcsetattr(fileno(f), TCSADRAIN, &new_termios) >= 0) {
                         size_t k;
 
+                        if (t != (usec_t) -1) {
+                                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);
@@ -2467,7 +2474,11 @@ int read_one_char(FILE *f, char *ret, bool *need_nl) {
                 }
         }
 
-        if (!(fgets(line, sizeof(line), f)))
+        if (t != (usec_t) -1)
+                if (fd_wait_for_event(fileno(f), POLLIN, t) <= 0)
+                        return -ETIMEDOUT;
+
+        if (!fgets(line, sizeof(line), f))
                 return -EIO;
 
         truncate_nl(line);
@@ -2509,7 +2520,8 @@ int ask(char *ret, const char *replies, const char *text, ...) {
 
                 fflush(stdout);
 
-                if ((r = read_one_char(stdin, &c, &need_nl)) < 0) {
+                r = read_one_char(stdin, &c, (usec_t) -1, &need_nl);
+                if (r < 0) {
 
                         if (r == -EBADMSG) {
                                 puts("Bad input, please try again.");
@@ -4079,6 +4091,39 @@ unsigned columns(void) {
         return parsed_columns;
 }
 
+int fd_lines(int fd) {
+        struct winsize ws;
+        zero(ws);
+
+        if (ioctl(fd, TIOCGWINSZ, &ws) < 0)
+                return -errno;
+
+        if (ws.ws_row <= 0)
+                return -EIO;
+
+        return ws.ws_row;
+}
+
+unsigned lines(void) {
+        static __thread int parsed_lines = 0;
+        const char *e;
+
+        if (_likely_(parsed_lines > 0))
+                return parsed_lines;
+
+        e = getenv("LINES");
+        if (e)
+                parsed_lines = atoi(e);
+
+        if (parsed_lines <= 0)
+                parsed_lines = fd_lines(STDOUT_FILENO);
+
+        if (parsed_lines <= 0)
+                parsed_lines = 25;
+
+        return parsed_lines;
+}
+
 int running_in_chroot(void) {
         struct stat a, b;
 
@@ -4850,7 +4895,7 @@ int pipe_eof(int fd) {
         return pollfd.revents & POLLHUP;
 }
 
-int fd_wait_for_event(int fd, int event) {
+int fd_wait_for_event(int fd, int event, usec_t t) {
         struct pollfd pollfd;
         int r;
 
@@ -4858,7 +4903,7 @@ int fd_wait_for_event(int fd, int event) {
         pollfd.fd = fd;
         pollfd.events = event;
 
-        r = poll(&pollfd, 1, -1);
+        r = poll(&pollfd, 1, t == (usec_t) -1 ? -1 : (int) (t / USEC_PER_MSEC));
         if (r < 0)
                 return -errno;
 
diff --git a/src/util.h b/src/util.h
index 1ce2440f3f..202d07a854 100644
--- a/src/util.h
+++ b/src/util.h
@@ -327,7 +327,7 @@ bool fstype_is_network(const char *fstype);
 
 int chvt(int vt);
 
-int read_one_char(FILE *f, char *ret, bool *need_nl);
+int read_one_char(FILE *f, char *ret, usec_t timeout, bool *need_nl);
 int ask(char *ret, const char *replies, const char *text, ...);
 
 int reset_terminal_fd(int fd);
@@ -384,6 +384,9 @@ void status_welcome(void);
 int fd_columns(int fd);
 unsigned columns(void);
 
+int fd_lines(int fd);
+unsigned lines(void);
+
 int running_in_chroot(void);
 
 char *ellipsize(const char *s, size_t length, unsigned percent);
@@ -525,7 +528,7 @@ unsigned long cap_last_cap(void);
 
 char *format_bytes(char *buf, size_t l, off_t t);
 
-int fd_wait_for_event(int fd, int event);
+int fd_wait_for_event(int fd, int event, usec_t timeout);
 
 void* memdup(const void *p, size_t l);