1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
4 This file is part of systemd.
6 Copyright 2010 Lennart Poettering
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.
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.
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/>.
22 #include <sys/types.h>
27 #include <sys/prctl.h>
33 static pid_t pager_pid = 0;
35 _noreturn_ static void pager_fallback(void) {
38 n = splice(STDIN_FILENO, NULL, STDOUT_FILENO, NULL, 64*1024, 0);
41 log_error("Internal pager failed: %m");
47 int pager_open(void) {
56 if ((pager = getenv("SYSTEMD_PAGER")) || (pager = getenv("PAGER")))
57 if (!*pager || streq(pager, "cat"))
63 /* Determine and cache number of columns before we spawn the
64 * pager so that we get the value from the actual tty */
68 log_error("Failed to create pager pipe: %m");
72 parent_pid = getpid();
77 log_error("Failed to fork pager: %m");
82 /* In the child start the pager */
85 dup2(fd[0], STDIN_FILENO);
88 setenv("LESS", "FRSX", 0);
90 /* Make sure the pager goes away when the parent dies */
91 if (prctl(PR_SET_PDEATHSIG, SIGTERM) < 0)
94 /* Check whether our parent died before we were able
95 * to set the death signal */
96 if (getppid() != parent_pid)
100 execlp(pager, pager, NULL);
101 execl("/bin/sh", "sh", "-c", pager, NULL);
104 /* Debian's alternatives command for pagers is
105 * called 'pager'. Note that we do not call
106 * sensible-pagers here, since that is just a
107 * shell script that implements a logic that
108 * is similar to this one anyway, but is
109 * Debian-specific. */
110 execlp("pager", "pager", NULL);
112 execlp("less", "less", NULL);
113 execlp("more", "more", NULL);
119 /* Return in the parent */
120 if (dup2(fd[1], STDOUT_FILENO) < 0) {
121 log_error("Failed to duplicate pager pipe: %m");
129 void pager_close(void) {
134 /* Inform pager that we are done */
136 kill(pager_pid, SIGCONT);
137 wait_for_terminate(pager_pid, NULL);
141 bool pager_have(void) {
142 return pager_pid > 0;