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Systemd/src/shared/pager.c
Zbigniew Jędrzejewski-Szmek ca78ad1de9 headers: remove unneeded includes from util.h 
This means we need to include many more headers in various files that simply
included util.h before, but it seems cleaner to do it this way.
2019-03-27 11:53:12 +01:00

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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 "fileio.h"
#include "io-util.h"
#include "locale-util.h"
#include "log.h"
#include "macro.h"
#include "pager.h"
#include "process-util.h"
#include "rlimit-util.h"
#include "signal-util.h"
#include "string-util.h"
#include "strv.h"
#include "terminal-util.h"
#include "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);
}
static int no_quit_on_interrupt(int exe_name_fd, const char *less_opts) {
_cleanup_fclose_ FILE *file = NULL;
_cleanup_free_ char *line = NULL;
int r;
assert(exe_name_fd >= 0);
assert(less_opts);
/* This takes ownership of exe_name_fd */
file = fdopen(exe_name_fd, "r");
if (!file) {
safe_close(exe_name_fd);
return log_error_errno(errno, "Failed to create FILE object: %m");
}
/* Find the last line */
for (;;) {
_cleanup_free_ char *t = NULL;
r = read_line(file, LONG_LINE_MAX, &t);
if (r < 0)
return log_error_errno(r, "Failed to read from socket: %m");
if (r == 0)
break;
free_and_replace(line, t);
}
/* We only treat "less" specially.
* Return true whenever option K is *not* set. */
r = streq_ptr(line, "less") && !strchr(less_opts, 'K');
log_debug("Pager executable is \"%s\", options \"%s\", quit_on_interrupt: %s",
strnull(line), less_opts, yes_no(!r));
return r;
}
int pager_open(PagerFlags flags) {
_cleanup_close_pair_ int fd[2] = { -1, -1 }, exe_name_pipe[2] = { -1, -1 };
_cleanup_strv_free_ char **pager_args = NULL;
const char *pager, *less_opts;
int r;
if (flags & PAGER_DISABLE)
return 0;
if (pager_pid > 0)
return 1;
if (terminal_is_dumb())
return 0;
if (!is_main_thread())
return log_error_errno(SYNTHETIC_ERRNO(EPERM), "Pager invoked from wrong thread.");
pager = getenv("SYSTEMD_PAGER");
if (!pager)
pager = getenv("PAGER");
if (pager) {
pager_args = strv_split(pager, WHITESPACE);
if (!pager_args)
return log_oom();
/* 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");
/* This is a pipe to feed the name of the executed pager binary into the parent */
if (pipe2(exe_name_pipe, O_CLOEXEC) < 0)
return log_error_errno(errno, "Failed to create exe_name pipe: %m");
/* Initialize a good set of less options */
less_opts = getenv("SYSTEMD_LESS");
if (!less_opts)
less_opts = "FRSXMK";
if (flags & PAGER_JUMP_TO_END)
less_opts = strjoina(less_opts, " +G");
r = safe_fork("(pager)", FORK_RESET_SIGNALS|FORK_DEATHSIG|FORK_RLIMIT_NOFILE_SAFE|FORK_LOG, &pager_pid);
if (r < 0)
return r;
if (r == 0) {
const char *less_charset, *exe;
/* In the child start the pager */
if (dup2(fd[0], STDIN_FILENO) < 0) {
log_error_errno(errno, "Failed to duplicate file descriptor to STDIN: %m");
_exit(EXIT_FAILURE);
}
safe_close_pair(fd);
if (setenv("LESS", less_opts, 1) < 0) {
log_error_errno(errno, "Failed to set environment variable LESS: %m");
_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) {
log_error_errno(errno, "Failed to set environment variable LESSCHARSET: %m");
_exit(EXIT_FAILURE);
}
if (pager_args) {
r = loop_write(exe_name_pipe[1], pager_args[0], strlen(pager_args[0]) + 1, false);
if (r < 0) {
log_error_errno(r, "Failed to write pager name to socket: %m");
_exit(EXIT_FAILURE);
}
execvp(pager_args[0], pager_args);
log_full_errno(errno == ENOENT ? LOG_DEBUG : LOG_WARNING, errno,
"Failed to execute '%s', using fallback pagers: %m", pager_args[0]);
}
/* 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. */
FOREACH_STRING(exe, "pager", "less", "more") {
r = loop_write(exe_name_pipe[1], exe, strlen(exe) + 1, false);
if (r < 0) {
log_error_errno(r, "Failed to write pager name to socket: %m");
_exit(EXIT_FAILURE);
}
execlp(exe, exe, NULL);
log_full_errno(errno == ENOENT ? LOG_DEBUG : LOG_WARNING, errno,
"Failed to execute '%s', using next fallback pager: %m", exe);
}
r = loop_write(exe_name_pipe[1], "(built-in)", strlen("(built-in") + 1, false);
if (r < 0) {
log_error_errno(r, "Failed to write pager name to socket: %m");
_exit(EXIT_FAILURE);
}
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;
exe_name_pipe[1] = safe_close(exe_name_pipe[1]);
r = no_quit_on_interrupt(TAKE_FD(exe_name_pipe[0]), less_opts);
if (r < 0)
return r;
if (r > 0)
(void) ignore_signals(SIGINT, -1);
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_RLIMIT_NOFILE_SAFE|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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