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