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 <fcntl.h>
  23 #include <stdlib.h>
  24 #include <unistd.h>
  25 #include <string.h>
  26 #include <sys/prctl.h>
  27
  28 #include "pager.h"
  29 #include "util.h"
  30 #include "process-util.h"
  31 #include "macro.h"
  32 #include "terminal-util.h"
  33 #include "signal-util.h"
  34 #include "copy.h"
  35
  36 static pid_t pager_pid = 0;
  37
  38 noreturn static void pager_fallback(void) {
  39         int r;
  40
  41         r = copy_bytes(STDIN_FILENO, STDOUT_FILENO, (off_t) -1, false);
  42         if (r < 0) {
  43                 log_error_errno(r, "Internal pager failed: %m");
  44                 _exit(EXIT_FAILURE);
  45         }
  46
  47         _exit(EXIT_SUCCESS);
  48 }
  49
  50 int pager_open(bool jump_to_end) {
  51         int fd[2];
  52         const char *pager;
  53         pid_t parent_pid;
  54         int r;
  55
  56         if (pager_pid > 0)
  57                 return 1;
  58
  59         if ((pager = getenv("SYSTEMD_PAGER")) || (pager = getenv("PAGER")))
  60                 if (!*pager || streq(pager, "cat"))
  61                         return 0;
  62
  63         if (!on_tty())
  64                 return 0;
  65
  66         /* Determine and cache number of columns before we spawn the
  67          * pager so that we get the value from the actual tty */
  68         columns();
  69
  70         if (pipe(fd) < 0)
  71                 return log_error_errno(errno, "Failed to create pager pipe: %m");
  72
  73         parent_pid = getpid();
  74
  75         pager_pid = fork();
  76         if (pager_pid < 0) {
  77                 r = -errno;
  78                 log_error_errno(errno, "Failed to fork pager: %m");
  79                 safe_close_pair(fd);
  80                 return r;
  81         }
  82
  83         /* In the child start the pager */
  84         if (pager_pid == 0) {
  85                 const char* less_opts, *less_charset;
  86
  87                 (void) reset_all_signal_handlers();
  88                 (void) reset_signal_mask();
  89
  90                 dup2(fd[0], STDIN_FILENO);
  91                 safe_close_pair(fd);
  92
  93                 /* Initialize a good set of less options */
  94                 less_opts = getenv("SYSTEMD_LESS");
  95                 if (!less_opts)
  96                         less_opts = "FRSXMK";
  97                 if (jump_to_end)
  98                         less_opts = strjoina(less_opts, " +G");
  99                 setenv("LESS", less_opts, 1);
 100
 101                 /* Initialize a good charset for less. This is
 102                  * particularly important if we output UTF-8
 103                  * characters. */
 104                 less_charset = getenv("SYSTEMD_LESSCHARSET");
 105                 if (!less_charset && is_locale_utf8())
 106                         less_charset = "utf-8";
 107                 if (less_charset)
 108                         setenv("LESSCHARSET", less_charset, 1);
 109
 110                 /* Make sure the pager goes away when the parent dies */
 111                 if (prctl(PR_SET_PDEATHSIG, SIGTERM) < 0)
 112                         _exit(EXIT_FAILURE);
 113
 114                 /* Check whether our parent died before we were able
 115                  * to set the death signal */
 116                 if (getppid() != parent_pid)
 117                         _exit(EXIT_SUCCESS);
 118
 119                 if (pager) {
 120                         execlp(pager, pager, NULL);
 121                         execl("/bin/sh", "sh", "-c", pager, NULL);
 122                 }
 123
 124                 /* Debian's alternatives command for pagers is
 125                  * called 'pager'. Note that we do not call
 126                  * sensible-pagers here, since that is just a
 127                  * shell script that implements a logic that
 128                  * is similar to this one anyway, but is
 129                  * Debian-specific. */
 130                 execlp("pager", "pager", NULL);
 131
 132                 execlp("less", "less", NULL);
 133                 execlp("more", "more", NULL);
 134
 135                 pager_fallback();
 136                 /* not reached */
 137         }
 138
 139         /* Return in the parent */
 140         if (dup2(fd[1], STDOUT_FILENO) < 0)
 141                 return log_error_errno(errno, "Failed to duplicate pager pipe: %m");
 142         if (dup2(fd[1], STDERR_FILENO) < 0)
 143                 return log_error_errno(errno, "Failed to duplicate pager pipe: %m");
 144
 145         safe_close_pair(fd);
 146         return 1;
 147 }
 148
 149 void pager_close(void) {
 150
 151         if (pager_pid <= 0)
 152                 return;
 153
 154         /* Inform pager that we are done */
 155         fclose(stdout);
 156         stdout = NULL;
 157
 158         fclose(stderr);
 159         stderr = NULL;
 160
 161         kill(pager_pid, SIGCONT);
 162         (void) wait_for_terminate(pager_pid, NULL);
 163         pager_pid = 0;
 164 }
 165
 166 bool pager_have(void) {
 167         return pager_pid > 0;
 168 }
 169
 170 int show_man_page(const char *desc, bool null_stdio) {
 171         const char *args[4] = { "man", NULL, NULL, NULL };
 172         char *e = NULL;
 173         pid_t pid;
 174         size_t k;
 175         int r;
 176         siginfo_t status;
 177
 178         k = strlen(desc);
 179
 180         if (desc[k-1] == ')')
 181                 e = strrchr(desc, '(');
 182
 183         if (e) {
 184                 char *page = NULL, *section = NULL;
 185
 186                 page = strndupa(desc, e - desc);
 187                 section = strndupa(e + 1, desc + k - e - 2);
 188
 189                 args[1] = section;
 190                 args[2] = page;
 191         } else
 192                 args[1] = desc;
 193
 194         pid = fork();
 195         if (pid < 0)
 196                 return log_error_errno(errno, "Failed to fork: %m");
 197
 198         if (pid == 0) {
 199                 /* Child */
 200
 201                 (void) reset_all_signal_handlers();
 202                 (void) reset_signal_mask();
 203
 204                 if (null_stdio) {
 205                         r = make_null_stdio();
 206                         if (r < 0) {
 207                                 log_error_errno(r, "Failed to kill stdio: %m");
 208                                 _exit(EXIT_FAILURE);
 209                         }
 210                 }
 211
 212                 execvp(args[0], (char**) args);
 213                 log_error_errno(errno, "Failed to execute man: %m");
 214                 _exit(EXIT_FAILURE);
 215         }
 216
 217         r = wait_for_terminate(pid, &status);
 218         if (r < 0)
 219                 return r;
 220
 221         log_debug("Exit code %i status %i", status.si_code, status.si_status);
 222         return status.si_status;
 223 }