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         fd_set exception;
  20
  21         FD_ZERO(&in);
  22         FD_ZERO(&exception);
  23         FD_SET(0, &in);
  24         FD_SET(0, &exception);
  25         select(1, &in, NULL, &exception, NULL);
  26
  27         setenv("LESS", "FRSX", 0);
  28 }
  29
  30 static const char *pager_argv[] = { "sh", "-c", NULL, NULL };
  31 static struct child_process pager_process;
  32
  33 static void wait_for_pager(void)
  34 {
  35         fflush(stdout);
  36         fflush(stderr);
  37         /* signal EOF to pager */
  38         close(1);
  39         close(2);
  40         finish_command(&pager_process);
  41 }
  42
  43 static void wait_for_pager_signal(int signo)
  44 {
  45         wait_for_pager();
  46         sigchain_pop(signo);
  47         raise(signo);
  48 }
  49
  50 void setup_pager(void)
  51 {
  52         const char *pager = getenv("PERF_PAGER");
  53
  54         if (!isatty(1))
  55                 return;
  56         if (!pager)
  57                 pager = getenv("PAGER");
  58         if (!(pager || access("/usr/bin/pager", X_OK)))
  59                 pager = "/usr/bin/pager";
  60         if (!(pager || access("/usr/bin/less", X_OK)))
  61                 pager = "/usr/bin/less";
  62         if (!pager)
  63                 pager = "cat";
  64         if (!*pager || !strcmp(pager, "cat"))
  65                 return;
  66
  67         spawned_pager = 1; /* means we are emitting to terminal */
  68
  69         /* spawn the pager */
  70         pager_argv[2] = pager;
  71         pager_process.argv = pager_argv;
  72         pager_process.in = -1;
  73         pager_process.preexec_cb = pager_preexec;
  74
  75         if (start_command(&pager_process))
  76                 return;
  77
  78         /* original process continues, but writes to the pipe */
  79         dup2(pager_process.in, 1);
  80         if (isatty(2))
  81                 dup2(pager_process.in, 2);
  82         close(pager_process.in);
  83
  84         /* this makes sure that the parent terminates after the pager */
  85         sigchain_push_common(wait_for_pager_signal);
  86         atexit(wait_for_pager);
  87 }
  88
  89 int pager_in_use(void)
  90 {
  91         const char *env;
  92
  93         if (spawned_pager)
  94                 return 1;
  95
  96         env = getenv("PERF_PAGER_IN_USE");
  97         return env ? perf_config_bool("PERF_PAGER_IN_USE", env) : 0;
  98 }