kernel/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
  10 static int spawned_pager;
  11
  12 static 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
  27 static const char *pager_argv[] = { "sh", "-c", NULL, NULL };
  28 static struct child_process pager_process;
  29
  30 static 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
  40 static void wait_for_pager_signal(int signo)
  41 {
  42         wait_for_pager();
  43         sigchain_pop(signo);
  44         raise(signo);
  45 }
  46
  47 void setup_pager(void)
  48 {
  49         const char *pager = getenv("PERF_PAGER");
  50
  51         if (!isatty(1))
  52                 return;
  53         if (!pager)
  54                 pager = getenv("PAGER");
  55         if (!(pager || access("/usr/bin/pager", X_OK)))
  56                 pager = "/usr/bin/pager";
  57         if (!(pager || access("/usr/bin/less", X_OK)))
  58                 pager = "/usr/bin/less";
  59         if (!pager)
  60                 pager = "cat";
  61         if (!*pager || !strcmp(pager, "cat"))
  62                 return;
  63
  64         spawned_pager = 1; /* means we are emitting to terminal */
  65
  66         /* spawn the pager */
  67         pager_argv[2] = pager;
  68         pager_process.argv = pager_argv;
  69         pager_process.in = -1;
  70         pager_process.preexec_cb = pager_preexec;
  71
  72         if (start_command(&pager_process))
  73                 return;
  74
  75         /* original process continues, but writes to the pipe */
  76         dup2(pager_process.in, 1);
  77         if (isatty(2))
  78                 dup2(pager_process.in, 2);
  79         close(pager_process.in);
  80
  81         /* this makes sure that the parent terminates after the pager */
  82         sigchain_push_common(wait_for_pager_signal);
  83         atexit(wait_for_pager);
  84 }
  85
  86 int pager_in_use(void)
  87 {
  88         const char *env;
  89
  90         if (spawned_pager)
  91                 return 1;
  92
  93         env = getenv("PERF_PAGER_IN_USE");
  94         return env ? perf_config_bool("PERF_PAGER_IN_USE", env) : 0;
  95 }