src/shared/pager.c

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