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, (uint64_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 = log_error_errno(errno, "Failed to fork pager: %m");
  78                 safe_close_pair(fd);
  79                 return r;
  80         }
  81
  82         /* In the child start the pager */
  83         if (pager_pid == 0) {
  84                 const char* less_opts, *less_charset;
  85
  86                 (void) reset_all_signal_handlers();
  87                 (void) reset_signal_mask();
  88
  89                 dup2(fd[0], STDIN_FILENO);
  90                 safe_close_pair(fd);
  91
  92                 /* Initialize a good set of less options */
  93                 less_opts = getenv("SYSTEMD_LESS");
  94                 if (!less_opts)
  95                         less_opts = "FRSXMK";
  96                 if (jump_to_end)
  97                         less_opts = strjoina(less_opts, " +G");
  98                 setenv("LESS", less_opts, 1);
  99
 100                 /* Initialize a good charset for less. This is
 101                  * particularly important if we output UTF-8
 102                  * characters. */
 103                 less_charset = getenv("SYSTEMD_LESSCHARSET");
 104                 if (!less_charset && is_locale_utf8())
 105                         less_charset = "utf-8";
 106                 if (less_charset)
 107                         setenv("LESSCHARSET", less_charset, 1);
 108
 109                 /* Make sure the pager goes away when the parent dies */
 110                 if (prctl(PR_SET_PDEATHSIG, SIGTERM) < 0)
 111                         _exit(EXIT_FAILURE);
 112
 113                 /* Check whether our parent died before we were able
 114                  * to set the death signal */
 115                 if (getppid() != parent_pid)
 116                         _exit(EXIT_SUCCESS);
 117
 118                 if (pager) {
 119                         execlp(pager, pager, NULL);
 120                         execl("/bin/sh", "sh", "-c", pager, NULL);
 121                 }
 122
 123                 /* Debian's alternatives command for pagers is
 124                  * called 'pager'. Note that we do not call
 125                  * sensible-pagers here, since that is just a
 126                  * shell script that implements a logic that
 127                  * is similar to this one anyway, but is
 128                  * Debian-specific. */
 129                 execlp("pager", "pager", NULL);
 130
 131                 execlp("less", "less", NULL);
 132                 execlp("more", "more", NULL);
 133
 134                 pager_fallback();
 135                 /* not reached */
 136         }
 137
 138         /* Return in the parent */
 139         if (dup2(fd[1], STDOUT_FILENO) < 0)
 140                 return log_error_errno(errno, "Failed to duplicate pager pipe: %m");
 141         if (dup2(fd[1], STDERR_FILENO) < 0)
 142                 return log_error_errno(errno, "Failed to duplicate pager pipe: %m");
 143
 144         safe_close_pair(fd);
 145         return 1;
 146 }
 147
 148 void pager_close(void) {
 149
 150         if (pager_pid <= 0)
 151                 return;
 152
 153         /* Inform pager that we are done */
 154         stdout = safe_fclose(stdout);
 155         stderr = safe_fclose(stderr);
 156
 157         (void) kill(pager_pid, SIGCONT);
 158         (void) wait_for_terminate(pager_pid, NULL);
 159         pager_pid = 0;
 160 }
 161
 162 bool pager_have(void) {
 163         return pager_pid > 0;
 164 }
 165
 166 int show_man_page(const char *desc, bool null_stdio) {
 167         const char *args[4] = { "man", NULL, NULL, NULL };
 168         char *e = NULL;
 169         pid_t pid;
 170         size_t k;
 171         int r;
 172         siginfo_t status;
 173
 174         k = strlen(desc);
 175
 176         if (desc[k-1] == ')')
 177                 e = strrchr(desc, '(');
 178
 179         if (e) {
 180                 char *page = NULL, *section = NULL;
 181
 182                 page = strndupa(desc, e - desc);
 183                 section = strndupa(e + 1, desc + k - e - 2);
 184
 185                 args[1] = section;
 186                 args[2] = page;
 187         } else
 188                 args[1] = desc;
 189
 190         pid = fork();
 191         if (pid < 0)
 192                 return log_error_errno(errno, "Failed to fork: %m");
 193
 194         if (pid == 0) {
 195                 /* Child */
 196
 197                 (void) reset_all_signal_handlers();
 198                 (void) reset_signal_mask();
 199
 200                 if (null_stdio) {
 201                         r = make_null_stdio();
 202                         if (r < 0) {
 203                                 log_error_errno(r, "Failed to kill stdio: %m");
 204                                 _exit(EXIT_FAILURE);
 205                         }
 206                 }
 207
 208                 execvp(args[0], (char**) args);
 209                 log_error_errno(errno, "Failed to execute man: %m");
 210                 _exit(EXIT_FAILURE);
 211         }
 212
 213         r = wait_for_terminate(pid, &status);
 214         if (r < 0)
 215                 return r;
 216
 217         log_debug("Exit code %i status %i", status.si_code, status.si_status);
 218         return status.si_status;
 219 }