tools/perf/util/pager.c

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