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