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 int pager_open(bool no_pager, bool jump_to_end) {
  57         _cleanup_close_pair_ int fd[2] = { -1, -1 };
  58         const char *pager;
  59         pid_t parent_pid;
  60
  61         if (no_pager)
  62                 return 0;
  63
  64         if (pager_pid > 0)
  65                 return 1;
  66
  67         if (terminal_is_dumb())
  68                 return 0;
  69
  70         pager = getenv("SYSTEMD_PAGER");
  71         if (!pager)
  72                 pager = getenv("PAGER");
  73
  74         /* If the pager is explicitly turned off, honour it */
  75         if (pager && STR_IN_SET(pager, "", "cat"))
  76                 return 0;
  77
  78         /* Determine and cache number of columns before we spawn the
  79          * pager so that we get the value from the actual tty */
  80         (void) columns();
  81
  82         if (pipe(fd) < 0)
  83                 return log_error_errno(errno, "Failed to create pager pipe: %m");
  84
  85         parent_pid = getpid();
  86
  87         pager_pid = fork();
  88         if (pager_pid < 0)
  89                 return log_error_errno(errno, "Failed to fork pager: %m");
  90
  91         /* In the child start the pager */
  92         if (pager_pid == 0) {
  93                 const char* less_opts, *less_charset;
  94
  95                 (void) reset_all_signal_handlers();
  96                 (void) reset_signal_mask();
  97
  98                 (void) dup2(fd[0], STDIN_FILENO);
  99                 safe_close_pair(fd);
 100
 101                 /* Initialize a good set of less options */
 102                 less_opts = getenv("SYSTEMD_LESS");
 103                 if (!less_opts)
 104                         less_opts = "FRSXMK";
 105                 if (jump_to_end)
 106                         less_opts = strjoina(less_opts, " +G");
 107                 setenv("LESS", less_opts, 1);
 108
 109                 /* Initialize a good charset for less. This is
 110                  * particularly important if we output UTF-8
 111                  * characters. */
 112                 less_charset = getenv("SYSTEMD_LESSCHARSET");
 113                 if (!less_charset && is_locale_utf8())
 114                         less_charset = "utf-8";
 115                 if (less_charset)
 116                         setenv("LESSCHARSET", less_charset, 1);
 117
 118                 /* Make sure the pager goes away when the parent dies */
 119                 if (prctl(PR_SET_PDEATHSIG, SIGTERM) < 0)
 120                         _exit(EXIT_FAILURE);
 121
 122                 /* Check whether our parent died before we were able
 123                  * to set the death signal */
 124                 if (getppid() != parent_pid)
 125                         _exit(EXIT_SUCCESS);
 126
 127                 if (pager) {
 128                         execlp(pager, pager, NULL);
 129                         execl("/bin/sh", "sh", "-c", pager, NULL);
 130                 }
 131
 132                 /* Debian's alternatives command for pagers is
 133                  * called 'pager'. Note that we do not call
 134                  * sensible-pagers here, since that is just a
 135                  * shell script that implements a logic that
 136                  * is similar to this one anyway, but is
 137                  * Debian-specific. */
 138                 execlp("pager", "pager", NULL);
 139
 140                 execlp("less", "less", NULL);
 141                 execlp("more", "more", NULL);
 142
 143                 pager_fallback();
 144                 /* not reached */
 145         }
 146
 147         /* Return in the parent */
 148         if (dup2(fd[1], STDOUT_FILENO) < 0)
 149                 return log_error_errno(errno, "Failed to duplicate pager pipe: %m");
 150         if (dup2(fd[1], STDERR_FILENO) < 0)
 151                 return log_error_errno(errno, "Failed to duplicate pager pipe: %m");
 152
 153         return 1;
 154 }
 155
 156 void pager_close(void) {
 157
 158         if (pager_pid <= 0)
 159                 return;
 160
 161         /* Inform pager that we are done */
 162         stdout = safe_fclose(stdout);
 163         stderr = safe_fclose(stderr);
 164
 165         (void) kill(pager_pid, SIGCONT);
 166         (void) wait_for_terminate(pager_pid, NULL);
 167         pager_pid = 0;
 168 }
 169
 170 bool pager_have(void) {
 171         return pager_pid > 0;
 172 }
 173
 174 int show_man_page(const char *desc, bool null_stdio) {
 175         const char *args[4] = { "man", NULL, NULL, NULL };
 176         char *e = NULL;
 177         pid_t pid;
 178         size_t k;
 179         int r;
 180         siginfo_t status;
 181
 182         k = strlen(desc);
 183
 184         if (desc[k-1] == ')')
 185                 e = strrchr(desc, '(');
 186
 187         if (e) {
 188                 char *page = NULL, *section = NULL;
 189
 190                 page = strndupa(desc, e - desc);
 191                 section = strndupa(e + 1, desc + k - e - 2);
 192
 193                 args[1] = section;
 194                 args[2] = page;
 195         } else
 196                 args[1] = desc;
 197
 198         pid = fork();
 199         if (pid < 0)
 200                 return log_error_errno(errno, "Failed to fork: %m");
 201
 202         if (pid == 0) {
 203                 /* Child */
 204
 205                 (void) reset_all_signal_handlers();
 206                 (void) reset_signal_mask();
 207
 208                 if (null_stdio) {
 209                         r = make_null_stdio();
 210                         if (r < 0) {
 211                                 log_error_errno(r, "Failed to kill stdio: %m");
 212                                 _exit(EXIT_FAILURE);
 213                         }
 214                 }
 215
 216                 execvp(args[0], (char**) args);
 217                 log_error_errno(errno, "Failed to execute man: %m");
 218                 _exit(EXIT_FAILURE);
 219         }
 220
 221         r = wait_for_terminate(pid, &status);
 222         if (r < 0)
 223                 return r;
 224
 225         log_debug("Exit code %i status %i", status.si_code, status.si_status);
 226         return status.si_status;
 227 }