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/*
* Pager: Routines to create a "more" running out of a particular file
* descriptor.
*
* Copyright 1987, 1988 by MIT Student Information Processing Board
*
* Permission to use, copy, modify, and distribute this software and
* its documentation for any purpose is hereby granted, provided that
* the names of M.I.T. and the M.I.T. S.I.P.B. not be used in
* advertising or publicity pertaining to distribution of the software
* without specific, written prior permission. M.I.T. and the
* M.I.T. S.I.P.B. make no representations about the suitability of
* this software for any purpose. It is provided "as is" without
* express or implied warranty.
*/
#include "config.h"
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef HAVE_ERRNO_H
#include <errno.h>
#else
extern int errno;
#endif
#include "ss_internal.h"
#include <stdio.h>
#include <sys/types.h>
#include <sys/file.h>
#include <signal.h>
#ifdef HAVE_SYS_PRCTL_H
#include <sys/prctl.h>
#else
#define PR_GET_DUMPABLE 3
#endif
#if (!defined(HAVE_PRCTL) && defined(linux))
#include <sys/syscall.h>
#endif
static char MORE[] = "more";
extern char *_ss_pager_name;
extern char *getenv PROTOTYPE((const char *));
char *ss_safe_getenv(const char *arg)
{
if ((getuid() != geteuid()) || (getgid() != getegid()))
return NULL;
#if HAVE_PRCTL
if (prctl(PR_GET_DUMPABLE, 0, 0, 0, 0) == 0)
return NULL;
#else
#if (defined(linux) && defined(SYS_prctl))
if (syscall(SYS_prctl, PR_GET_DUMPABLE, 0, 0, 0, 0) == 0)
return NULL;
#endif
#endif
#ifdef HAVE___SECURE_GETENV
return __secure_getenv(arg);
#else
return getenv(arg);
#endif
}
/*
* this needs a *lot* of work....
*
* run in same process
* handle SIGINT sensibly
* allow finer control -- put-page-break-here
*/
#ifndef NO_FORK
int ss_pager_create(void)
{
int filedes[2];
if (pipe(filedes) != 0)
return(-1);
switch(fork()) {
case -1:
return(-1);
case 0:
/*
* Child; dup read half to 0, close all but 0, 1, and 2
*/
if (dup2(filedes[0], 0) == -1)
exit(1);
ss_page_stdin();
default:
/*
* Parent: close "read" side of pipe, return
* "write" side.
*/
(void) close(filedes[0]);
return(filedes[1]);
}
}
#else /* don't fork */
int ss_pager_create()
{
int fd;
fd = open("/dev/tty", O_WRONLY, 0);
return fd;
}
#endif
static int write_all(int fd, char *buf, size_t count)
{
ssize_t ret;
int c = 0;
while (count > 0) {
ret = write(fd, buf, count);
if (ret < 0) {
if ((errno == EAGAIN) || (errno == EINTR))
continue;
return -1;
}
count -= ret;
buf += ret;
c += ret;
}
return c;
}
void ss_page_stdin()
{
int i;
sigset_t mask;
for (i = 3; i < 32; i++)
(void) close(i);
(void) signal(SIGINT, SIG_DFL);
sigprocmask(SIG_BLOCK, 0, &mask);
sigdelset(&mask, SIGINT);
sigprocmask(SIG_SETMASK, &mask, 0);
if (_ss_pager_name == (char *)NULL) {
if ((_ss_pager_name = ss_safe_getenv("PAGER")) == (char *)NULL)
_ss_pager_name = MORE;
}
(void) execlp(_ss_pager_name, _ss_pager_name, (char *) NULL);
{
/* minimal recovery if pager program isn't found */
char buf[80];
register int n;
while ((n = read(0, buf, 80)) > 0)
write_all(1, buf, n);
}
exit(errno);
}
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