src/shared/pager.c

   1 /***
   2   This file is part of systemd.
   3
   4   Copyright 2010 Lennart Poettering
   5
   6   systemd is free software; you can redistribute it and/or modify it
   7   under the terms of the GNU Lesser General Public License as published by
   8   the Free Software Foundation; either version 2.1 of the License, or
   9   (at your option) any later version.
  10
  11   systemd is distributed in the hope that it will be useful, but
  12   WITHOUT ANY WARRANTY; without even the implied warranty of
  13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14   Lesser General Public License for more details.
  15
  16   You should have received a copy of the GNU Lesser General Public License
  17   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  18 ***/
  19
  20 #include <errno.h>
  21 #include <signal.h>
  22 #include <stddef.h>
  23 #include <stdint.h>
  24 #include <stdio.h>
  25 #include <stdlib.h>
  26 #include <string.h>
  27 #include <sys/prctl.h>
  28 #include <unistd.h>
  29
  30 #include "copy.h"
  31 #include "fd-util.h"
  32 #include "locale-util.h"
  33 #include "log.h"
  34 #include "macro.h"
  35 #include "pager.h"
  36 #include "process-util.h"
  37 #include "signal-util.h"
  38 #include "string-util.h"
  39 #include "strv.h"
  40 #include "terminal-util.h"
  41
  42 static pid_t pager_pid = 0;
  43
  44 noreturn static void pager_fallback(void) {
  45         int r;
  46
  47         r = copy_bytes(STDIN_FILENO, STDOUT_FILENO, (uint64_t) -1, 0);
  48         if (r < 0) {
  49                 log_error_errno(r, "Internal pager failed: %m");
  50                 _exit(EXIT_FAILURE);
  51         }
  52
  53         _exit(EXIT_SUCCESS);
  54 }
  55
  56 static int stored_stdout = -1;
  57 static int stored_stderr = -1;
  58 static bool stdout_redirected = false;
  59 static bool stderr_redirected = false;
  60
  61 int pager_open(bool no_pager, bool jump_to_end) {
  62         _cleanup_close_pair_ int fd[2] = { -1, -1 };
  63         const char *pager;
  64         pid_t parent_pid;
  65
  66         if (no_pager)
  67                 return 0;
  68
  69         if (pager_pid > 0)
  70                 return 1;
  71
  72         if (terminal_is_dumb())
  73                 return 0;
  74
  75         pager = getenv("SYSTEMD_PAGER");
  76         if (!pager)
  77                 pager = getenv("PAGER");
  78
  79         /* If the pager is explicitly turned off, honour it */
  80         if (pager && STR_IN_SET(pager, "", "cat"))
  81                 return 0;
  82
  83         /* Determine and cache number of columns/lines before we spawn the pager so that we get the value from the
  84          * actual tty */
  85         (void) columns();
  86         (void) lines();
  87
  88         if (pipe2(fd, O_CLOEXEC) < 0)
  89                 return log_error_errno(errno, "Failed to create pager pipe: %m");
  90
  91         parent_pid = getpid_cached();
  92
  93         pager_pid = fork();
  94         if (pager_pid < 0)
  95                 return log_error_errno(errno, "Failed to fork pager: %m");
  96
  97         /* In the child start the pager */
  98         if (pager_pid == 0) {
  99                 const char* less_opts, *less_charset;
 100
 101                 (void) reset_all_signal_handlers();
 102                 (void) reset_signal_mask();
 103
 104                 (void) dup2(fd[0], STDIN_FILENO);
 105                 safe_close_pair(fd);
 106
 107                 /* Initialize a good set of less options */
 108                 less_opts = getenv("SYSTEMD_LESS");
 109                 if (!less_opts)
 110                         less_opts = "FRSXMK";
 111                 if (jump_to_end)
 112                         less_opts = strjoina(less_opts, " +G");
 113                 if (setenv("LESS", less_opts, 1) < 0)
 114                         _exit(EXIT_FAILURE);
 115
 116                 /* Initialize a good charset for less. This is
 117                  * particularly important if we output UTF-8
 118                  * characters. */
 119                 less_charset = getenv("SYSTEMD_LESSCHARSET");
 120                 if (!less_charset && is_locale_utf8())
 121                         less_charset = "utf-8";
 122                 if (less_charset &&
 123                     setenv("LESSCHARSET", less_charset, 1) < 0)
 124                         _exit(EXIT_FAILURE);
 125
 126                 /* Make sure the pager goes away when the parent dies */
 127                 if (prctl(PR_SET_PDEATHSIG, SIGTERM) < 0)
 128                         _exit(EXIT_FAILURE);
 129
 130                 /* Check whether our parent died before we were able
 131                  * to set the death signal */
 132                 if (getppid() != parent_pid)
 133                         _exit(EXIT_SUCCESS);
 134
 135                 if (pager) {
 136                         execlp(pager, pager, NULL);
 137                         execl("/bin/sh", "sh", "-c", pager, NULL);
 138                 }
 139
 140                 /* Debian's alternatives command for pagers is
 141                  * called 'pager'. Note that we do not call
 142                  * sensible-pagers here, since that is just a
 143                  * shell script that implements a logic that
 144                  * is similar to this one anyway, but is
 145                  * Debian-specific. */
 146                 execlp("pager", "pager", NULL);
 147
 148                 execlp("less", "less", NULL);
 149                 execlp("more", "more", NULL);
 150
 151                 pager_fallback();
 152                 /* not reached */
 153         }
 154
 155         /* Return in the parent */
 156         stored_stdout = fcntl(STDOUT_FILENO, F_DUPFD_CLOEXEC, 3);
 157         if (dup2(fd[1], STDOUT_FILENO) < 0) {
 158                 stored_stdout = safe_close(stored_stdout);
 159                 return log_error_errno(errno, "Failed to duplicate pager pipe: %m");
 160         }
 161         stdout_redirected = true;
 162
 163         stored_stderr = fcntl(STDERR_FILENO, F_DUPFD_CLOEXEC, 3);
 164         if (dup2(fd[1], STDERR_FILENO) < 0) {
 165                 stored_stderr = safe_close(stored_stderr);
 166                 return log_error_errno(errno, "Failed to duplicate pager pipe: %m");
 167         }
 168         stderr_redirected = true;
 169
 170         return 1;
 171 }
 172
 173 void pager_close(void) {
 174
 175         if (pager_pid <= 0)
 176                 return;
 177
 178         /* Inform pager that we are done */
 179         (void) fflush(stdout);
 180         if (stdout_redirected)
 181                 if (stored_stdout < 0 || dup2(stored_stdout, STDOUT_FILENO) < 0)
 182                         (void) close(STDOUT_FILENO);
 183         stored_stdout = safe_close(stored_stdout);
 184         (void) fflush(stderr);
 185         if (stderr_redirected)
 186                 if (stored_stderr < 0 || dup2(stored_stderr, STDERR_FILENO) < 0)
 187                         (void) close(STDERR_FILENO);
 188         stored_stderr = safe_close(stored_stderr);
 189         stdout_redirected = stderr_redirected = false;
 190
 191         (void) kill(pager_pid, SIGCONT);
 192         (void) wait_for_terminate(pager_pid, NULL);
 193         pager_pid = 0;
 194 }
 195
 196 bool pager_have(void) {
 197         return pager_pid > 0;
 198 }
 199
 200 int show_man_page(const char *desc, bool null_stdio) {
 201         const char *args[4] = { "man", NULL, NULL, NULL };
 202         char *e = NULL;
 203         pid_t pid;
 204         size_t k;
 205         int r;
 206         siginfo_t status;
 207
 208         k = strlen(desc);
 209
 210         if (desc[k-1] == ')')
 211                 e = strrchr(desc, '(');
 212
 213         if (e) {
 214                 char *page = NULL, *section = NULL;
 215
 216                 page = strndupa(desc, e - desc);
 217                 section = strndupa(e + 1, desc + k - e - 2);
 218
 219                 args[1] = section;
 220                 args[2] = page;
 221         } else
 222                 args[1] = desc;
 223
 224         pid = fork();
 225         if (pid < 0)
 226                 return log_error_errno(errno, "Failed to fork: %m");
 227
 228         if (pid == 0) {
 229                 /* Child */
 230
 231                 (void) reset_all_signal_handlers();
 232                 (void) reset_signal_mask();
 233
 234                 if (null_stdio) {
 235                         r = make_null_stdio();
 236                         if (r < 0) {
 237                                 log_error_errno(r, "Failed to kill stdio: %m");
 238                                 _exit(EXIT_FAILURE);
 239                         }
 240                 }
 241
 242                 execvp(args[0], (char**) args);
 243                 log_error_errno(errno, "Failed to execute man: %m");
 244                 _exit(EXIT_FAILURE);
 245         }
 246
 247         r = wait_for_terminate(pid, &status);
 248         if (r < 0)
 249                 return r;
 250
 251         log_debug("Exit code %i status %i", status.si_code, status.si_status);
 252         return status.si_status;
 253 }