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150 lines
4.1 KiB
C
150 lines
4.1 KiB
C
/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
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/***
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This file is part of systemd.
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Copyright 2010 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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***/
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#include <sys/types.h>
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#include <fcntl.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <string.h>
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#include <sys/prctl.h>
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#include "pager.h"
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#include "util.h"
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#include "macro.h"
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static pid_t pager_pid = 0;
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noreturn static void pager_fallback(void) {
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ssize_t n;
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do {
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n = splice(STDIN_FILENO, NULL, STDOUT_FILENO, NULL, 64*1024, 0);
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} while (n > 0);
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if (n < 0) {
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log_error("Internal pager failed: %m");
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_exit(EXIT_FAILURE);
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}
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_exit(EXIT_SUCCESS);
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}
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int pager_open(bool jump_to_end) {
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int fd[2];
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const char *pager;
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pid_t parent_pid;
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int r;
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if (pager_pid > 0)
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return 1;
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if ((pager = getenv("SYSTEMD_PAGER")) || (pager = getenv("PAGER")))
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if (!*pager || streq(pager, "cat"))
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return 0;
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if (!on_tty())
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return 0;
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/* Determine and cache number of columns before we spawn the
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* pager so that we get the value from the actual tty */
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columns();
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if (pipe(fd) < 0) {
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log_error("Failed to create pager pipe: %m");
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return -errno;
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}
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parent_pid = getpid();
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pager_pid = fork();
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if (pager_pid < 0) {
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r = -errno;
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log_error("Failed to fork pager: %m");
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close_pipe(fd);
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return r;
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}
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/* In the child start the pager */
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if (pager_pid == 0) {
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dup2(fd[0], STDIN_FILENO);
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close_pipe(fd);
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if (jump_to_end)
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setenv("LESS", "FRSXMK+G", 1);
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else
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setenv("LESS", "FRSXMK", 1);
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/* Make sure the pager goes away when the parent dies */
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if (prctl(PR_SET_PDEATHSIG, SIGTERM) < 0)
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_exit(EXIT_FAILURE);
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/* Check whether our parent died before we were able
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* to set the death signal */
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if (getppid() != parent_pid)
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_exit(EXIT_SUCCESS);
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if (pager) {
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execlp(pager, pager, NULL);
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execl("/bin/sh", "sh", "-c", pager, NULL);
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}
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/* Debian's alternatives command for pagers is
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* called 'pager'. Note that we do not call
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* sensible-pagers here, since that is just a
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* shell script that implements a logic that
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* is similar to this one anyway, but is
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* Debian-specific. */
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execlp("pager", "pager", NULL);
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execlp("less", "less", NULL);
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execlp("more", "more", NULL);
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pager_fallback();
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/* not reached */
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}
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/* Return in the parent */
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if (dup2(fd[1], STDOUT_FILENO) < 0) {
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log_error("Failed to duplicate pager pipe: %m");
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return -errno;
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}
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close_pipe(fd);
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return 1;
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}
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void pager_close(void) {
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if (pager_pid <= 0)
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return;
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/* Inform pager that we are done */
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fclose(stdout);
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kill(pager_pid, SIGCONT);
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wait_for_terminate(pager_pid, NULL);
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pager_pid = 0;
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}
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bool pager_have(void) {
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return pager_pid > 0;
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}
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