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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 <fcntl.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;
_noreturn_ static void pager_fallback(void) {
ssize_t n;
do {
n = splice(STDIN_FILENO, NULL, STDOUT_FILENO, NULL, 64*1024, 0);
} while (n > 0);
if (n < 0) {
log_error("Internal pager failed: %m");
_exit(EXIT_FAILURE);
}
_exit(EXIT_SUCCESS);
}
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);
pager_fallback();
/* not reached */
}
/* 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;
}
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