1 // SPDX-License-Identifier: GPL-2.0
2 #include <sys/select.h>
3 #include <stdlib.h>
4 #include <stdio.h>
5 #include <string.h>
6 #include <signal.h>
7 #include <sys/ioctl.h>
8 #include "pager.h"
9 #include "run-command.h"
10 #include "sigchain.h"
11 #include "subcmd-config.h"
12
13 /*
14 * This is split up from the rest of git so that we can do
15 * something different on Windows.
16 */
17
18 static int spawned_pager;
19 static int pager_columns;
20
pager_init(const char * pager_env)21 void pager_init(const char *pager_env)
22 {
23 subcmd_config.pager_env = pager_env;
24 }
25
26 static const char *forced_pager;
27
force_pager(const char * pager)28 void force_pager(const char *pager)
29 {
30 forced_pager = pager;
31 }
32
pager_preexec(void)33 static void pager_preexec(void)
34 {
35 /*
36 * Work around bug in "less" by not starting it until we
37 * have real input
38 */
39 fd_set in;
40 fd_set exception;
41
42 FD_ZERO(&in);
43 FD_ZERO(&exception);
44 FD_SET(0, &in);
45 FD_SET(0, &exception);
46 select(1, &in, NULL, &exception, NULL);
47
48 setenv("LESS", "FRSX", 0);
49 }
50
51 static const char *pager_argv[] = { "sh", "-c", NULL, NULL };
52 static struct child_process pager_process;
53
wait_for_pager(void)54 static void wait_for_pager(void)
55 {
56 fflush(stdout);
57 fflush(stderr);
58 /* signal EOF to pager */
59 close(1);
60 close(2);
61 finish_command(&pager_process);
62 }
63
wait_for_pager_signal(int signo)64 static void wait_for_pager_signal(int signo)
65 {
66 wait_for_pager();
67 sigchain_pop(signo);
68 raise(signo);
69 }
70
setup_pager(void)71 void setup_pager(void)
72 {
73 const char *pager = getenv(subcmd_config.pager_env);
74 struct winsize sz;
75
76 if (forced_pager)
77 pager = forced_pager;
78 if (!isatty(1) && !forced_pager)
79 return;
80 if (ioctl(1, TIOCGWINSZ, &sz) == 0)
81 pager_columns = sz.ws_col;
82 if (!pager)
83 pager = getenv("PAGER");
84 if (!(pager || access("/usr/bin/pager", X_OK)))
85 pager = "/usr/bin/pager";
86 if (!(pager || access("/usr/bin/less", X_OK)))
87 pager = "/usr/bin/less";
88 if (!pager)
89 pager = "cat";
90 if (!*pager || !strcmp(pager, "cat"))
91 return;
92
93 spawned_pager = 1; /* means we are emitting to terminal */
94
95 /* spawn the pager */
96 pager_argv[2] = pager;
97 pager_process.argv = pager_argv;
98 pager_process.in = -1;
99 pager_process.preexec_cb = pager_preexec;
100
101 if (start_command(&pager_process))
102 return;
103
104 /* original process continues, but writes to the pipe */
105 dup2(pager_process.in, 1);
106 if (isatty(2))
107 dup2(pager_process.in, 2);
108 close(pager_process.in);
109
110 /* this makes sure that the parent terminates after the pager */
111 sigchain_push_common(wait_for_pager_signal);
112 atexit(wait_for_pager);
113 }
114
pager_in_use(void)115 int pager_in_use(void)
116 {
117 return spawned_pager;
118 }
119
pager_get_columns(void)120 int pager_get_columns(void)
121 {
122 char *s;
123
124 s = getenv("COLUMNS");
125 if (s)
126 return atoi(s);
127
128 return (pager_columns ? pager_columns : 80) - 2;
129 }
130