pager.c revision 2eec67acbb00593e414549a7e5b35eb7dd776b1b
/*-*- 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 Lesser General Public License as published by
the Free Software Foundation; either version 2.1 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#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_errno(errno, "Internal pager failed: %m");
_exit(EXIT_FAILURE);
}
_exit(EXIT_SUCCESS);
}
int pager_open(bool jump_to_end) {
int fd[2];
const char *pager;
pid_t parent_pid;
int r;
if (pager_pid > 0)
return 1;
if ((pager = getenv("SYSTEMD_PAGER")) || (pager = getenv("PAGER")))
if (!*pager || streq(pager, "cat"))
return 0;
if (!on_tty())
return 0;
/* 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)
return log_error_errno(errno, "Failed to create pager pipe: %m");
parent_pid = getpid();
pager_pid = fork();
if (pager_pid < 0) {
r = -errno;
log_error_errno(errno, "Failed to fork pager: %m");
safe_close_pair(fd);
return r;
}
/* In the child start the pager */
if (pager_pid == 0) {
const char* less_opts;
dup2(fd[0], STDIN_FILENO);
safe_close_pair(fd);
less_opts = getenv("SYSTEMD_LESS");
if (!less_opts)
less_opts = "FRSXMK";
if (jump_to_end)
less_opts = strjoina(less_opts, " +G");
setenv("LESS", less_opts, 1);
/* 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)
return log_error_errno(errno, "Failed to duplicate pager pipe: %m");
safe_close_pair(fd);
return 1;
}
void pager_close(void) {
if (pager_pid <= 0)
return;
/* Inform pager that we are done */
fclose(stdout);
kill(pager_pid, SIGCONT);
(void) wait_for_terminate(pager_pid, NULL);
pager_pid = 0;
}
bool pager_have(void) {
return pager_pid > 0;
}
int show_man_page(const char *desc, bool null_stdio) {
const char *args[4] = { "man", NULL, NULL, NULL };
char *e = NULL;
pid_t pid;
size_t k;
int r;
siginfo_t status;
k = strlen(desc);
if (desc[k-1] == ')')
e = strrchr(desc, '(');
if (e) {
char *page = NULL, *section = NULL;
page = strndupa(desc, e - desc);
section = strndupa(e + 1, desc + k - e - 2);
args[1] = section;
args[2] = page;
} else
args[1] = desc;
pid = fork();
if (pid < 0)
return log_error_errno(errno, "Failed to fork: %m");
if (pid == 0) {
/* Child */
if (null_stdio) {
r = make_null_stdio();
if (r < 0) {
log_error_errno(r, "Failed to kill stdio: %m");
_exit(EXIT_FAILURE);
}
}
execvp(args[0], (char**) args);
log_error_errno(errno, "Failed to execute man: %m");
_exit(EXIT_FAILURE);
}
r = wait_for_terminate(pid, &status);
if (r < 0)
return r;
log_debug("Exit code %i status %i", status.si_code, status.si_status);
return status.si_status;
}