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 <sys/ioctl.h>
   7 #include "pager.h"
   8 #include "run-command.h"
   9 #include "sigchain.h"
  10 #include "subcmd-config.h"
  11
  12 /*
  13  * This is split up from the rest of git so that we can do
  14  * something different on Windows.
  15  */
  16
  17 static int spawned_pager;
  18 static int pager_columns;
  19
  20 void pager_init(const char *pager_env)
  21 {
  22         subcmd_config.pager_env = pager_env;
  23 }
  24
  25 static void pager_preexec(void)
  26 {
  27         /*
  28          * Work around bug in "less" by not starting it until we
  29          * have real input
  30          */
  31         fd_set in;
  32
  33         FD_ZERO(&in);
  34         FD_SET(0, &in);
  35         select(1, &in, NULL, &in, NULL);
  36
  37         setenv("LESS", "FRSX", 0);
  38 }
  39
  40 static const char *pager_argv[] = { "sh", "-c", NULL, NULL };
  41 static struct child_process pager_process;
  42
  43 static void wait_for_pager(void)
  44 {
  45         fflush(stdout);
  46         fflush(stderr);
  47         /* signal EOF to pager */
  48         close(1);
  49         close(2);
  50         finish_command(&pager_process);
  51 }
  52
  53 static void wait_for_pager_signal(int signo)
  54 {
  55         wait_for_pager();
  56         sigchain_pop(signo);
  57         raise(signo);
  58 }
  59
  60 void setup_pager(void)
  61 {
  62         const char *pager = getenv(subcmd_config.pager_env);
  63         struct winsize sz;
  64
  65         if (!isatty(1))
  66                 return;
  67         if (ioctl(1, TIOCGWINSZ, &sz) == 0)
  68                 pager_columns = sz.ws_col;
  69         if (!pager)
  70                 pager = getenv("PAGER");
  71         if (!(pager || access("/usr/bin/pager", X_OK)))
  72                 pager = "/usr/bin/pager";
  73         if (!(pager || access("/usr/bin/less", X_OK)))
  74                 pager = "/usr/bin/less";
  75         if (!pager)
  76                 pager = "cat";
  77         if (!*pager || !strcmp(pager, "cat"))
  78                 return;
  79
  80         spawned_pager = 1; /* means we are emitting to terminal */
  81
  82         /* spawn the pager */
  83         pager_argv[2] = pager;
  84         pager_process.argv = pager_argv;
  85         pager_process.in = -1;
  86         pager_process.preexec_cb = pager_preexec;
  87
  88         if (start_command(&pager_process))
  89                 return;
  90
  91         /* original process continues, but writes to the pipe */
  92         dup2(pager_process.in, 1);
  93         if (isatty(2))
  94                 dup2(pager_process.in, 2);
  95         close(pager_process.in);
  96
  97         /* this makes sure that the parent terminates after the pager */
  98         sigchain_push_common(wait_for_pager_signal);
  99         atexit(wait_for_pager);
 100 }
 101
 102 int pager_in_use(void)
 103 {
 104         return spawned_pager;
 105 }
 106
 107 int pager_get_columns(void)
 108 {
 109         char *s;
 110
 111         s = getenv("COLUMNS");
 112         if (s)
 113                 return atoi(s);
 114
 115         return (pager_columns ? pager_columns : 80) - 2;
 116 }