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/*
* This code is based on Linux perf tools (so in turn git) project
* which is released under GPL v2.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/select.h>
#include <sys/wait.h>
#include <unistd.h>
static int pager_pid;
static int pager_fd;
static int start_command(const char *argv[])
{
int fds[2];
if (pipe(fds) < 0)
return -1;
fflush(NULL);
pager_pid = fork();
if (pager_pid < 0) {
close(fds[0]);
close(fds[1]);
return -1;
}
if (!pager_pid) {
fd_set in_set;
fd_set ex_set;
/* child process */
dup2(fds[0], STDIN_FILENO);
close(fds[0]);
close(fds[1]);
FD_ZERO(&in_set);
FD_ZERO(&ex_set);
FD_SET(STDIN_FILENO, &in_set);
FD_SET(STDIN_FILENO, &ex_set);
/*
* Work around bug in "less" by not starting it
* until we have real input
*/
select(1, &in_set, NULL, &ex_set, NULL);
setenv("LESS", "FRSX", 0);
execvp(argv[0], (char *const *)argv);
exit(127);
}
close(fds[0]);
pager_fd = fds[1];
return 0;
}
void wait_for_pager(void)
{
int status;
if (!pager_pid)
return;
/* signal EOF to pager */
fclose(stdout);
fclose(stderr);
waitpid(pager_pid, &status, 0);
pager_pid = 0;
}
char *setup_pager(void)
{
char *pager = getenv("PAGER");
if (!isatty(STDOUT_FILENO))
return NULL;
if (!(pager || access("/usr/bin/pager", X_OK)))
pager = "/usr/bin/pager";
if (!(pager || access("/usr/bin/less", X_OK)))
pager = "/usr/bin/less";
if (!pager)
pager = "cat";
if (!*pager || !strcmp(pager, "cat"))
return NULL;
return pager;
}
void start_pager(char *pager)
{
const char *pager_argv[] = { "sh", "-c", NULL, NULL };
if (pager == NULL)
return;
/* spawn the pager */
pager_argv[2] = pager;
if (start_command(pager_argv))
return;
/* original process continues, but writes to the pipe */
dup2(pager_fd, STDOUT_FILENO);
if (isatty(STDERR_FILENO))
dup2(pager_fd, STDERR_FILENO);
close(pager_fd);
atexit(wait_for_pager);
}
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