tools/lib/subcmd/pager.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <sys/select.h>
   3 #include <stdlib.h>
   4 #include <stdio.h>
   5 #include <string.h>
   6 #include <signal.h>
   7 #include <sys/ioctl.h>
   8 #include "pager.h"
   9 #include "run-command.h"
  10 #include "sigchain.h"
  11 #include "subcmd-config.h"
  12
  13 /*
  14  * This is split up from the rest of git so that we can do
  15  * something different on Windows.
  16  */
  17
  18 static int spawned_pager;
  19 static int pager_columns;
  20
  21 void pager_init(const char *pager_env)
  22 {
  23         subcmd_config.pager_env = pager_env;
  24 }
  25
  26 static void pager_preexec(void)
  27 {
  28         /*
  29          * Work around bug in "less" by not starting it until we
  30          * have real input
  31          */
  32         fd_set in;
  33
  34         FD_ZERO(&in);
  35         FD_SET(0, &in);
  36         select(1, &in, NULL, &in, NULL);
  37
  38         setenv("LESS", "FRSX", 0);
  39 }
  40
  41 static const char *pager_argv[] = { "sh", "-c", NULL, NULL };
  42 static struct child_process pager_process;
  43
  44 static void wait_for_pager(void)
  45 {
  46         fflush(stdout);
  47         fflush(stderr);
  48         /* signal EOF to pager */
  49         close(1);
  50         close(2);
  51         finish_command(&pager_process);
  52 }
  53
  54 static void wait_for_pager_signal(int signo)
  55 {
  56         wait_for_pager();
  57         sigchain_pop(signo);
  58         raise(signo);
  59 }
  60
  61 void setup_pager(void)
  62 {
  63         const char *pager = getenv(subcmd_config.pager_env);
  64         struct winsize sz;
  65
  66         if (!isatty(1))
  67                 return;
  68         if (ioctl(1, TIOCGWINSZ, &sz) == 0)
  69                 pager_columns = sz.ws_col;
  70         if (!pager)
  71                 pager = getenv("PAGER");
  72         if (!(pager || access("/usr/bin/pager", X_OK)))
  73                 pager = "/usr/bin/pager";
  74         if (!(pager || access("/usr/bin/less", X_OK)))
  75                 pager = "/usr/bin/less";
  76         if (!pager)
  77                 pager = "cat";
  78         if (!*pager || !strcmp(pager, "cat"))
  79                 return;
  80
  81         spawned_pager = 1; /* means we are emitting to terminal */
  82
  83         /* spawn the pager */
  84         pager_argv[2] = pager;
  85         pager_process.argv = pager_argv;
  86         pager_process.in = -1;
  87         pager_process.preexec_cb = pager_preexec;
  88
  89         if (start_command(&pager_process))
  90                 return;
  91
  92         /* original process continues, but writes to the pipe */
  93         dup2(pager_process.in, 1);
  94         if (isatty(2))
  95                 dup2(pager_process.in, 2);
  96         close(pager_process.in);
  97
  98         /* this makes sure that the parent terminates after the pager */
  99         sigchain_push_common(wait_for_pager_signal);
 100         atexit(wait_for_pager);
 101 }
 102
 103 int pager_in_use(void)
 104 {
 105         return spawned_pager;
 106 }
 107
 108 int pager_get_columns(void)
 109 {
 110         char *s;
 111
 112         s = getenv("COLUMNS");
 113         if (s)
 114                 return atoi(s);
 115
 116         return (pager_columns ? pager_columns : 80) - 2;
 117 }