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-rw-r--r--src/pager.c122
1 files changed, 122 insertions, 0 deletions
diff --git a/src/pager.c b/src/pager.c
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+++ b/src/pager.c
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+/*-*- 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 (isatty(STDOUT_FILENO) <= 0)
+ return;
+
+ if ((pager = getenv("SYSTEMD_PAGER")) || (pager = getenv("PAGER")))
+ if (!*pager || streq(pager, "cat"))
+ 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;
+}