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git.ipfire.org Git - thirdparty/systemd.git/blob - src/shared/pager.c
1 /* SPDX-License-Identifier: LGPL-2.1+ */
10 #include <sys/prctl.h>
17 #include "locale-util.h"
21 #include "process-util.h"
22 #include "rlimit-util.h"
23 #include "signal-util.h"
24 #include "string-util.h"
26 #include "terminal-util.h"
28 static pid_t pager_pid
= 0;
30 static int stored_stdout
= -1;
31 static int stored_stderr
= -1;
32 static bool stdout_redirected
= false;
33 static bool stderr_redirected
= false;
35 _noreturn_
static void pager_fallback(void) {
38 r
= copy_bytes(STDIN_FILENO
, STDOUT_FILENO
, (uint64_t) -1, 0);
40 log_error_errno(r
, "Internal pager failed: %m");
47 static int no_quit_on_interrupt(int exe_name_fd
, const char *less_opts
) {
48 _cleanup_fclose_
FILE *file
= NULL
;
49 _cleanup_free_
char *line
= NULL
;
52 assert(exe_name_fd
>= 0);
55 /* This takes ownership of exe_name_fd */
56 file
= fdopen(exe_name_fd
, "r");
58 safe_close(exe_name_fd
);
59 return log_error_errno(errno
, "Failed to create FILE object: %m");
62 /* Find the last line */
64 _cleanup_free_
char *t
= NULL
;
66 r
= read_line(file
, LONG_LINE_MAX
, &t
);
68 return log_error_errno(r
, "Failed to read from socket: %m");
72 free_and_replace(line
, t
);
75 /* We only treat "less" specially.
76 * Return true whenever option K is *not* set. */
77 r
= streq_ptr(line
, "less") && !strchr(less_opts
, 'K');
79 log_debug("Pager executable is \"%s\", options \"%s\", quit_on_interrupt: %s",
80 strnull(line
), less_opts
, yes_no(!r
));
84 int pager_open(PagerFlags flags
) {
85 _cleanup_close_pair_
int fd
[2] = { -1, -1 }, exe_name_pipe
[2] = { -1, -1 };
86 _cleanup_strv_free_
char **pager_args
= NULL
;
87 const char *pager
, *less_opts
;
90 if (flags
& PAGER_DISABLE
)
96 if (terminal_is_dumb())
99 if (!is_main_thread())
100 return log_error_errno(SYNTHETIC_ERRNO(EPERM
), "Pager invoked from wrong thread.");
102 pager
= getenv("SYSTEMD_PAGER");
104 pager
= getenv("PAGER");
107 pager_args
= strv_split(pager
, WHITESPACE
);
111 /* If the pager is explicitly turned off, honour it */
112 if (strv_isempty(pager_args
) || strv_equal(pager_args
, STRV_MAKE("cat")))
116 /* Determine and cache number of columns/lines before we spawn the pager so that we get the value from the
121 if (pipe2(fd
, O_CLOEXEC
) < 0)
122 return log_error_errno(errno
, "Failed to create pager pipe: %m");
124 /* This is a pipe to feed the name of the executed pager binary into the parent */
125 if (pipe2(exe_name_pipe
, O_CLOEXEC
) < 0)
126 return log_error_errno(errno
, "Failed to create exe_name pipe: %m");
128 /* Initialize a good set of less options */
129 less_opts
= getenv("SYSTEMD_LESS");
131 less_opts
= "FRSXMK";
132 if (flags
& PAGER_JUMP_TO_END
)
133 less_opts
= strjoina(less_opts
, " +G");
135 r
= safe_fork("(pager)", FORK_RESET_SIGNALS
|FORK_DEATHSIG
|FORK_RLIMIT_NOFILE_SAFE
|FORK_LOG
, &pager_pid
);
139 const char *less_charset
, *exe
;
141 /* In the child start the pager */
143 if (dup2(fd
[0], STDIN_FILENO
) < 0) {
144 log_error_errno(errno
, "Failed to duplicate file descriptor to STDIN: %m");
150 if (setenv("LESS", less_opts
, 1) < 0) {
151 log_error_errno(errno
, "Failed to set environment variable LESS: %m");
155 /* Initialize a good charset for less. This is
156 * particularly important if we output UTF-8
158 less_charset
= getenv("SYSTEMD_LESSCHARSET");
159 if (!less_charset
&& is_locale_utf8())
160 less_charset
= "utf-8";
162 setenv("LESSCHARSET", less_charset
, 1) < 0) {
163 log_error_errno(errno
, "Failed to set environment variable LESSCHARSET: %m");
168 r
= loop_write(exe_name_pipe
[1], pager_args
[0], strlen(pager_args
[0]) + 1, false);
170 log_error_errno(r
, "Failed to write pager name to socket: %m");
174 execvp(pager_args
[0], pager_args
);
175 log_full_errno(errno
== ENOENT
? LOG_DEBUG
: LOG_WARNING
, errno
,
176 "Failed to execute '%s', using fallback pagers: %m", pager_args
[0]);
179 /* Debian's alternatives command for pagers is
180 * called 'pager'. Note that we do not call
181 * sensible-pagers here, since that is just a
182 * shell script that implements a logic that
183 * is similar to this one anyway, but is
184 * Debian-specific. */
185 FOREACH_STRING(exe
, "pager", "less", "more") {
186 r
= loop_write(exe_name_pipe
[1], exe
, strlen(exe
) + 1, false);
188 log_error_errno(r
, "Failed to write pager name to socket: %m");
191 execlp(exe
, exe
, NULL
);
192 log_full_errno(errno
== ENOENT
? LOG_DEBUG
: LOG_WARNING
, errno
,
193 "Failed to execute '%s', using next fallback pager: %m", exe
);
196 r
= loop_write(exe_name_pipe
[1], "(built-in)", strlen("(built-in") + 1, false);
198 log_error_errno(r
, "Failed to write pager name to socket: %m");
205 /* Return in the parent */
206 stored_stdout
= fcntl(STDOUT_FILENO
, F_DUPFD_CLOEXEC
, 3);
207 if (dup2(fd
[1], STDOUT_FILENO
) < 0) {
208 stored_stdout
= safe_close(stored_stdout
);
209 return log_error_errno(errno
, "Failed to duplicate pager pipe: %m");
211 stdout_redirected
= true;
213 stored_stderr
= fcntl(STDERR_FILENO
, F_DUPFD_CLOEXEC
, 3);
214 if (dup2(fd
[1], STDERR_FILENO
) < 0) {
215 stored_stderr
= safe_close(stored_stderr
);
216 return log_error_errno(errno
, "Failed to duplicate pager pipe: %m");
218 stderr_redirected
= true;
220 exe_name_pipe
[1] = safe_close(exe_name_pipe
[1]);
222 r
= no_quit_on_interrupt(TAKE_FD(exe_name_pipe
[0]), less_opts
);
226 (void) ignore_signals(SIGINT
, -1);
231 void pager_close(void) {
236 /* Inform pager that we are done */
237 (void) fflush(stdout
);
238 if (stdout_redirected
)
239 if (stored_stdout
< 0 || dup2(stored_stdout
, STDOUT_FILENO
) < 0)
240 (void) close(STDOUT_FILENO
);
241 stored_stdout
= safe_close(stored_stdout
);
242 (void) fflush(stderr
);
243 if (stderr_redirected
)
244 if (stored_stderr
< 0 || dup2(stored_stderr
, STDERR_FILENO
) < 0)
245 (void) close(STDERR_FILENO
);
246 stored_stderr
= safe_close(stored_stderr
);
247 stdout_redirected
= stderr_redirected
= false;
249 (void) kill(pager_pid
, SIGCONT
);
250 (void) wait_for_terminate(pager_pid
, NULL
);
254 bool pager_have(void) {
255 return pager_pid
> 0;
258 int show_man_page(const char *desc
, bool null_stdio
) {
259 const char *args
[4] = { "man", NULL
, NULL
, NULL
};
267 if (desc
[k
-1] == ')')
268 e
= strrchr(desc
, '(');
271 char *page
= NULL
, *section
= NULL
;
273 page
= strndupa(desc
, e
- desc
);
274 section
= strndupa(e
+ 1, desc
+ k
- e
- 2);
281 r
= safe_fork("(man)", FORK_RESET_SIGNALS
|FORK_DEATHSIG
|(null_stdio
? FORK_NULL_STDIO
: 0)|FORK_RLIMIT_NOFILE_SAFE
|FORK_LOG
, &pid
);
286 execvp(args
[0], (char**) args
);
287 log_error_errno(errno
, "Failed to execute man: %m");
291 return wait_for_terminate_and_check(NULL
, pid
, 0);