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/* SPDX-License-Identifier: LGPL-2.1+ */
#include <errno.h>
#include <signal.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/prctl.h>
#include <unistd.h>
#include "copy.h"
#include "fd-util.h"
#include "locale-util.h"
#include "log.h"
#include "macro.h"
#include "pager.h"
#include "process-util.h"
#include "signal-util.h"
#include "string-util.h"
#include "strv.h"
#include "terminal-util.h"
static pid_t pager_pid = 0;
static int stored_stdout = -1;
static int stored_stderr = -1;
static bool stdout_redirected = false;
static bool stderr_redirected = false;
_noreturn_ static void pager_fallback(void) {
int r;
r = copy_bytes(STDIN_FILENO, STDOUT_FILENO, (uint64_t) -1, 0);
if (r < 0) {
log_error_errno(r, "Internal pager failed: %m");
_exit(EXIT_FAILURE);
}
_exit(EXIT_SUCCESS);
}
int pager_open(bool no_pager, bool jump_to_end) {
_cleanup_close_pair_ int fd[2] = { -1, -1 };
_cleanup_strv_free_ char **pager_args = NULL;
const char *pager;
int r;
if (no_pager)
return 0;
if (pager_pid > 0)
return 1;
if (terminal_is_dumb())
return 0;
if (!is_main_thread())
return -EPERM;
pager = getenv("SYSTEMD_PAGER");
if (!pager)
pager = getenv("PAGER");
if (pager) {
pager_args = strv_split(pager, WHITESPACE);
if (!pager_args)
return -ENOMEM;
/* If the pager is explicitly turned off, honour it */
if (strv_isempty(pager_args) || strv_equal(pager_args, STRV_MAKE("cat")))
return 0;
}
/* Determine and cache number of columns/lines before we spawn the pager so that we get the value from the
* actual tty */
(void) columns();
(void) lines();
if (pipe2(fd, O_CLOEXEC) < 0)
return log_error_errno(errno, "Failed to create pager pipe: %m");
r = safe_fork("(pager)", FORK_RESET_SIGNALS|FORK_DEATHSIG|FORK_LOG, &pager_pid);
if (r < 0)
return r;
if (r == 0) {
const char* less_opts, *less_charset;
/* In the child start the pager */
(void) dup2(fd[0], STDIN_FILENO);
safe_close_pair(fd);
/* Initialize a good set of less options */
less_opts = getenv("SYSTEMD_LESS");
if (!less_opts)
less_opts = "FRSXMK";
if (jump_to_end)
less_opts = strjoina(less_opts, " +G");
if (setenv("LESS", less_opts, 1) < 0)
_exit(EXIT_FAILURE);
/* Initialize a good charset for less. This is
* particularly important if we output UTF-8
* characters. */
less_charset = getenv("SYSTEMD_LESSCHARSET");
if (!less_charset && is_locale_utf8())
less_charset = "utf-8";
if (less_charset &&
setenv("LESSCHARSET", less_charset, 1) < 0)
_exit(EXIT_FAILURE);
if (pager_args)
execvp(pager_args[0], pager_args);
/* 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 */
stored_stdout = fcntl(STDOUT_FILENO, F_DUPFD_CLOEXEC, 3);
if (dup2(fd[1], STDOUT_FILENO) < 0) {
stored_stdout = safe_close(stored_stdout);
return log_error_errno(errno, "Failed to duplicate pager pipe: %m");
}
stdout_redirected = true;
stored_stderr = fcntl(STDERR_FILENO, F_DUPFD_CLOEXEC, 3);
if (dup2(fd[1], STDERR_FILENO) < 0) {
stored_stderr = safe_close(stored_stderr);
return log_error_errno(errno, "Failed to duplicate pager pipe: %m");
}
stderr_redirected = true;
return 1;
}
void pager_close(void) {
if (pager_pid <= 0)
return;
/* Inform pager that we are done */
(void) fflush(stdout);
if (stdout_redirected)
if (stored_stdout < 0 || dup2(stored_stdout, STDOUT_FILENO) < 0)
(void) close(STDOUT_FILENO);
stored_stdout = safe_close(stored_stdout);
(void) fflush(stderr);
if (stderr_redirected)
if (stored_stderr < 0 || dup2(stored_stderr, STDERR_FILENO) < 0)
(void) close(STDERR_FILENO);
stored_stderr = safe_close(stored_stderr);
stdout_redirected = stderr_redirected = false;
(void) 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;
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;
r = safe_fork("(man)", FORK_RESET_SIGNALS|FORK_DEATHSIG|(null_stdio ? FORK_NULL_STDIO : 0)|FORK_LOG, &pid);
if (r < 0)
return r;
if (r == 0) {
/* Child */
execvp(args[0], (char**) args);
log_error_errno(errno, "Failed to execute man: %m");
_exit(EXIT_FAILURE);
}
return wait_for_terminate_and_check(NULL, pid, 0);
}
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