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
 17static int spawned_pager;
 18static int pager_columns;
 19
 20void pager_init(const char *pager_env)
 21{
 22	subcmd_config.pager_env = pager_env;
 23}
 24
 25static 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
 40static const char *pager_argv[] = { "sh", "-c", NULL, NULL };
 41static struct child_process pager_process;
 42
 43static 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
 53static void wait_for_pager_signal(int signo)
 54{
 55	wait_for_pager();
 56	sigchain_pop(signo);
 57	raise(signo);
 58}
 59
 60void 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
102int pager_in_use(void)
103{
104	return spawned_pager;
105}
106
107int 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}