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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> | |
23 | #include <stdlib.h> | |
24 | #include <unistd.h> | |
25 | #include <string.h> | |
26 | #include <sys/prctl.h> | |
27 | ||
28 | #include "pager.h" | |
29 | #include "util.h" | |
30 | #include "macro.h" | |
31 | ||
32 | static pid_t pager_pid = 0; | |
33 | ||
34 | void pager_open(void) { | |
35 | int fd[2]; | |
36 | const char *pager; | |
37 | pid_t parent_pid; | |
38 | ||
39 | if (pager_pid > 0) | |
40 | return; | |
41 | ||
1968a360 LP |
42 | if ((pager = getenv("SYSTEMD_PAGER")) || (pager = getenv("PAGER"))) |
43 | if (!*pager || streq(pager, "cat")) | |
44 | return; | |
45 | ||
729e3769 LP |
46 | if (isatty(STDOUT_FILENO) <= 0) |
47 | return; | |
48 | ||
1968a360 LP |
49 | /* Determine and cache number of columns before we spawn the |
50 | * pager so that we get the value from the actual tty */ | |
51 | columns(); | |
52 | ||
53 | if (pipe(fd) < 0) { | |
54 | log_error("Failed to create pager pipe: %m"); | |
55 | return; | |
56 | } | |
57 | ||
58 | parent_pid = getpid(); | |
59 | ||
60 | pager_pid = fork(); | |
61 | if (pager_pid < 0) { | |
62 | log_error("Failed to fork pager: %m"); | |
63 | close_pipe(fd); | |
64 | return; | |
65 | } | |
66 | ||
67 | /* In the child start the pager */ | |
68 | if (pager_pid == 0) { | |
69 | ||
70 | dup2(fd[0], STDIN_FILENO); | |
71 | close_pipe(fd); | |
72 | ||
73 | setenv("LESS", "FRSX", 0); | |
74 | ||
75 | /* Make sure the pager goes away when the parent dies */ | |
76 | if (prctl(PR_SET_PDEATHSIG, SIGTERM) < 0) | |
77 | _exit(EXIT_FAILURE); | |
78 | ||
79 | /* Check whether our parent died before we were able | |
80 | * to set the death signal */ | |
81 | if (getppid() != parent_pid) | |
82 | _exit(EXIT_SUCCESS); | |
83 | ||
84 | if (pager) { | |
85 | execlp(pager, pager, NULL); | |
86 | execl("/bin/sh", "sh", "-c", pager, NULL); | |
87 | } | |
88 | ||
89 | /* Debian's alternatives command for pagers is | |
90 | * called 'pager'. Note that we do not call | |
91 | * sensible-pagers here, since that is just a | |
92 | * shell script that implements a logic that | |
93 | * is similar to this one anyway, but is | |
94 | * Debian-specific. */ | |
95 | execlp("pager", "pager", NULL); | |
96 | ||
97 | execlp("less", "less", NULL); | |
98 | execlp("more", "more", NULL); | |
99 | execlp("cat", "cat", NULL); | |
100 | ||
101 | log_error("Unable to execute pager: %m"); | |
102 | _exit(EXIT_FAILURE); | |
103 | } | |
104 | ||
105 | /* Return in the parent */ | |
106 | if (dup2(fd[1], STDOUT_FILENO) < 0) | |
107 | log_error("Failed to duplicate pager pipe: %m"); | |
108 | ||
109 | close_pipe(fd); | |
110 | } | |
111 | ||
112 | void pager_close(void) { | |
113 | ||
114 | if (pager_pid <= 0) | |
115 | return; | |
116 | ||
117 | /* Inform pager that we are done */ | |
118 | fclose(stdout); | |
119 | kill(pager_pid, SIGCONT); | |
120 | wait_for_terminate(pager_pid, NULL); | |
121 | pager_pid = 0; | |
122 | } |