pager.c

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#include "cache.h"
#include "run-command.h"
#include "sigchain.h"

/*
 * This is split up from the rest of git so that we can do
 * something different on Windows.
 */

static int spawned_pager;

static void pager_preexec(void)
{
    /*
     * Work around bug in "less" by not starting it until we
     * have real input
     */
    fd_set in;

    FD_ZERO(&in);
    FD_SET(0, &in);
    select(1, &in, NULL, &in, NULL);

    setenv("LESS", "FRSX", 0);
}

static const char *pager_argv[] = { "sh", "-c", NULL, NULL };
static struct child_process pager_process;

static void wait_for_pager(void)
{
    fflush(stdout);
    fflush(stderr);
    /* signal EOF to pager */
    close(1);
    close(2);
    finish_command(&pager_process);
}

static void wait_for_pager_signal(int signo)
{
    wait_for_pager();
    sigchain_pop(signo);
    raise(signo);
}

void setup_pager(void)
{
    const char *pager = getenv("PERF_PAGER");

    if (!isatty(1))
        return;
    if (!pager) {
        if (!pager_program)
            perf_config(perf_default_config, NULL);
        pager = pager_program;
    }
    if (!pager)
        pager = getenv("PAGER");
    if (!pager) {
        if (!access("/usr/bin/pager", X_OK))
            pager = "/usr/bin/pager";
    }
    if (!pager)
        pager = "less";
    else if (!*pager || !strcmp(pager, "cat"))
        return;

    spawned_pager = 1; /* means we are emitting to terminal */

    /* spawn the pager */
    pager_argv[2] = pager;
    pager_process.argv = pager_argv;
    pager_process.in = -1;
    pager_process.preexec_cb = pager_preexec;

    if (start_command(&pager_process))
        return;

    /* original process continues, but writes to the pipe */
    dup2(pager_process.in, 1);
    if (isatty(2))
        dup2(pager_process.in, 2);
    close(pager_process.in);

    /* this makes sure that the parent terminates after the pager */
    sigchain_push_common(wait_for_pager_signal);
    atexit(wait_for_pager);
}

int pager_in_use(void)
{
    const char *env;

    if (spawned_pager)
        return 1;

    env = getenv("PERF_PAGER_IN_USE");
    return env ? perf_config_bool("PERF_PAGER_IN_USE", env) : 0;
}