Root/tools/perf/util/pager.c

1#include "cache.h"
2#include "run-command.h"
3#include "sigchain.h"
4
5/*
6 * This is split up from the rest of git so that we can do
7 * something different on Windows.
8 */
9
10static int spawned_pager;
11
12static void pager_preexec(void)
13{
14    /*
15     * Work around bug in "less" by not starting it until we
16     * have real input
17     */
18    fd_set in;
19
20    FD_ZERO(&in);
21    FD_SET(0, &in);
22    select(1, &in, NULL, &in, NULL);
23
24    setenv("LESS", "FRSX", 0);
25}
26
27static const char *pager_argv[] = { "sh", "-c", NULL, NULL };
28static struct child_process pager_process;
29
30static void wait_for_pager(void)
31{
32    fflush(stdout);
33    fflush(stderr);
34    /* signal EOF to pager */
35    close(1);
36    close(2);
37    finish_command(&pager_process);
38}
39
40static void wait_for_pager_signal(int signo)
41{
42    wait_for_pager();
43    sigchain_pop(signo);
44    raise(signo);
45}
46
47void setup_pager(void)
48{
49    const char *pager = getenv("PERF_PAGER");
50
51    if (!isatty(1))
52        return;
53    if (!pager) {
54        if (!pager_program)
55            perf_config(perf_default_config, NULL);
56        pager = pager_program;
57    }
58    if (!pager)
59        pager = getenv("PAGER");
60    if (!pager)
61        pager = "less";
62    else if (!*pager || !strcmp(pager, "cat"))
63        return;
64
65    spawned_pager = 1; /* means we are emitting to terminal */
66
67    /* spawn the pager */
68    pager_argv[2] = pager;
69    pager_process.argv = pager_argv;
70    pager_process.in = -1;
71    pager_process.preexec_cb = pager_preexec;
72
73    if (start_command(&pager_process))
74        return;
75
76    /* original process continues, but writes to the pipe */
77    dup2(pager_process.in, 1);
78    if (isatty(2))
79        dup2(pager_process.in, 2);
80    close(pager_process.in);
81
82    /* this makes sure that the parent terminates after the pager */
83    sigchain_push_common(wait_for_pager_signal);
84    atexit(wait_for_pager);
85}
86
87int pager_in_use(void)
88{
89    const char *env;
90
91    if (spawned_pager)
92        return 1;
93
94    env = getenv("PERF_PAGER_IN_USE");
95    return env ? perf_config_bool("PERF_PAGER_IN_USE", env) : 0;
96}
97

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