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1968a360 LP |
1 | /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/ |
2 | ||
3 | /*** | |
4 | This file is part of systemd. | |
5 | ||
6 | Copyright 2010 Lennart Poettering | |
7 | ||
8 | systemd is free software; you can redistribute it and/or modify it | |
9 | under the terms of the GNU General Public License as published by | |
10 | the Free Software Foundation; either version 2 of the License, or | |
11 | (at your option) any later version. | |
12 | ||
13 | systemd is distributed in the hope that it will be useful, but | |
14 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
16 | General Public License for more details. | |
17 | ||
18 | You should have received a copy of the GNU General Public License | |
19 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
20 | ***/ | |
21 | ||
22 | #include <sys/types.h> | |
4a8e40eb | 23 | #include <fcntl.h> |
1968a360 LP |
24 | #include <stdlib.h> |
25 | #include <unistd.h> | |
26 | #include <string.h> | |
27 | #include <sys/prctl.h> | |
28 | ||
29 | #include "pager.h" | |
30 | #include "util.h" | |
31 | #include "macro.h" | |
32 | ||
33 | static pid_t pager_pid = 0; | |
34 | ||
4a8e40eb MS |
35 | static void pager_fallback(void) { |
36 | ssize_t n; | |
37 | do { | |
38 | n = splice(STDIN_FILENO, NULL, STDOUT_FILENO, NULL, 64*1024, 0); | |
39 | } while (n > 0); | |
40 | if (n < 0) { | |
41 | log_error("Internal pager failed: %m"); | |
42 | _exit(EXIT_FAILURE); | |
43 | } | |
44 | _exit(EXIT_SUCCESS); | |
45 | } | |
46 | ||
1968a360 LP |
47 | void pager_open(void) { |
48 | int fd[2]; | |
49 | const char *pager; | |
50 | pid_t parent_pid; | |
51 | ||
52 | if (pager_pid > 0) | |
53 | return; | |
54 | ||
1968a360 LP |
55 | if ((pager = getenv("SYSTEMD_PAGER")) || (pager = getenv("PAGER"))) |
56 | if (!*pager || streq(pager, "cat")) | |
57 | return; | |
58 | ||
729e3769 LP |
59 | if (isatty(STDOUT_FILENO) <= 0) |
60 | return; | |
61 | ||
1968a360 LP |
62 | /* Determine and cache number of columns before we spawn the |
63 | * pager so that we get the value from the actual tty */ | |
64 | columns(); | |
65 | ||
66 | if (pipe(fd) < 0) { | |
67 | log_error("Failed to create pager pipe: %m"); | |
68 | return; | |
69 | } | |
70 | ||
71 | parent_pid = getpid(); | |
72 | ||
73 | pager_pid = fork(); | |
74 | if (pager_pid < 0) { | |
75 | log_error("Failed to fork pager: %m"); | |
76 | close_pipe(fd); | |
77 | return; | |
78 | } | |
79 | ||
80 | /* In the child start the pager */ | |
81 | if (pager_pid == 0) { | |
82 | ||
83 | dup2(fd[0], STDIN_FILENO); | |
84 | close_pipe(fd); | |
85 | ||
86 | setenv("LESS", "FRSX", 0); | |
87 | ||
88 | /* Make sure the pager goes away when the parent dies */ | |
89 | if (prctl(PR_SET_PDEATHSIG, SIGTERM) < 0) | |
90 | _exit(EXIT_FAILURE); | |
91 | ||
92 | /* Check whether our parent died before we were able | |
93 | * to set the death signal */ | |
94 | if (getppid() != parent_pid) | |
95 | _exit(EXIT_SUCCESS); | |
96 | ||
97 | if (pager) { | |
98 | execlp(pager, pager, NULL); | |
99 | execl("/bin/sh", "sh", "-c", pager, NULL); | |
100 | } | |
101 | ||
102 | /* Debian's alternatives command for pagers is | |
103 | * called 'pager'. Note that we do not call | |
104 | * sensible-pagers here, since that is just a | |
105 | * shell script that implements a logic that | |
106 | * is similar to this one anyway, but is | |
107 | * Debian-specific. */ | |
108 | execlp("pager", "pager", NULL); | |
109 | ||
110 | execlp("less", "less", NULL); | |
111 | execlp("more", "more", NULL); | |
1968a360 | 112 | |
4a8e40eb MS |
113 | pager_fallback(); |
114 | /* not reached */ | |
1968a360 LP |
115 | } |
116 | ||
117 | /* Return in the parent */ | |
118 | if (dup2(fd[1], STDOUT_FILENO) < 0) | |
119 | log_error("Failed to duplicate pager pipe: %m"); | |
120 | ||
121 | close_pipe(fd); | |
122 | } | |
123 | ||
124 | void pager_close(void) { | |
125 | ||
126 | if (pager_pid <= 0) | |
127 | return; | |
128 | ||
129 | /* Inform pager that we are done */ | |
130 | fclose(stdout); | |
131 | kill(pager_pid, SIGCONT); | |
132 | wait_for_terminate(pager_pid, NULL); | |
133 | pager_pid = 0; | |
134 | } |