summaryrefslogtreecommitdiff
path: root/src/shared/pager.c
blob: 8d60f8a7a10993614f26eecb8552c1b2ea48ff17 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
/***
  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 <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 "terminal-util.h"

static pid_t pager_pid = 0;

noreturn static void pager_fallback(void) {
        int r;

        r = copy_bytes(STDIN_FILENO, STDOUT_FILENO, (uint64_t) -1, false);
        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 };
        const char *pager;
        pid_t parent_pid;

        if (no_pager)
                return 0;

        if (pager_pid > 0)
                return 1;

        if (!on_tty())
                        return 0;

        pager = getenv("SYSTEMD_PAGER");
        if (!pager)
                pager = getenv("PAGER");

        /* If the pager is explicitly turned off, honour it */
        if (pager && (pager[0] == 0 || streq(pager, "cat")))
                return 0;

        /* Determine and cache number of columns before we spawn the
         * pager so that we get the value from the actual tty */
        (void) 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)
                return log_error_errno(errno, "Failed to fork pager: %m");

        /* In the child start the pager */
        if (pager_pid == 0) {
                const char* less_opts, *less_charset;

                (void) reset_all_signal_handlers();
                (void) reset_signal_mask();

                (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");
                setenv("LESS", less_opts, 1);

                /* 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);

                /* 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");
        if (dup2(fd[1], STDERR_FILENO) < 0)
                return log_error_errno(errno, "Failed to duplicate pager pipe: %m");

        return 1;
}

void pager_close(void) {

        if (pager_pid <= 0)
                return;

        /* Inform pager that we are done */
#if defined(__GLIBC__)
        stdout = safe_fclose(stdout);
        stderr = safe_fclose(stderr);
#else
        (void) safe_fclose(stdout);
        (void) safe_fclose(stderr);
#endif // in musl-libc these are const

        (void) kill(pager_pid, SIGCONT);
        (void) wait_for_terminate(pager_pid, NULL);
        pager_pid = 0;
}

bool pager_have(void) {
        return pager_pid > 0;
}

#if 0 /// UNNEEDED by elogind
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 */

                (void) reset_all_signal_handlers();
                (void) reset_signal_mask();

                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;
}
#endif // 0