tools/lib/subcmd/pager.c

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