124 lines
3.4 KiB
C
124 lines
3.4 KiB
C
/* Test whether a file descriptor is a pipe.
|
|
|
|
Copyright (C) 2006, 2008-2020 Free Software Foundation, Inc.
|
|
|
|
This program is free software: you can redistribute it and/or modify
|
|
it under the terms of the GNU General Public License as published by
|
|
the Free Software Foundation; either version 3 of the License, or
|
|
(at your option) any later version.
|
|
|
|
This program is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
GNU General Public License for more details.
|
|
|
|
You should have received a copy of the GNU General Public License
|
|
along with this program. If not, see <https://www.gnu.org/licenses/>. */
|
|
|
|
/* Written by Paul Eggert. */
|
|
|
|
#include <config.h>
|
|
|
|
#include "isapipe.h"
|
|
|
|
#include <errno.h>
|
|
|
|
#if defined _WIN32 && ! defined __CYGWIN__
|
|
/* Windows platforms. */
|
|
|
|
/* Get GetFileType. */
|
|
# include <windows.h>
|
|
|
|
/* Get _get_osfhandle. */
|
|
# if GNULIB_MSVC_NOTHROW
|
|
# include "msvc-nothrow.h"
|
|
# else
|
|
# include <io.h>
|
|
# endif
|
|
|
|
int
|
|
isapipe (int fd)
|
|
{
|
|
HANDLE h = (HANDLE) _get_osfhandle (fd);
|
|
|
|
if (h == INVALID_HANDLE_VALUE)
|
|
{
|
|
errno = EBADF;
|
|
return -1;
|
|
}
|
|
|
|
return (GetFileType (h) == FILE_TYPE_PIPE);
|
|
}
|
|
|
|
#else
|
|
/* Unix platforms. */
|
|
|
|
# include <stdbool.h>
|
|
# include <sys/types.h>
|
|
# include <sys/stat.h>
|
|
# include <unistd.h>
|
|
|
|
/* The maximum link count for pipes; (nlink_t) -1 if not known. */
|
|
# ifndef PIPE_LINK_COUNT_MAX
|
|
# define PIPE_LINK_COUNT_MAX ((nlink_t) (-1))
|
|
# endif
|
|
|
|
/* Return 1 if FD is a pipe, 0 if not, -1 (setting errno) on error.
|
|
|
|
Test fairly strictly whether FD is a pipe. lseek and checking for
|
|
ESPIPE does not suffice, since many non-pipe files cause lseek to
|
|
fail with errno == ESPIPE. */
|
|
|
|
int
|
|
isapipe (int fd)
|
|
{
|
|
nlink_t pipe_link_count_max = PIPE_LINK_COUNT_MAX;
|
|
bool check_for_fifo = (HAVE_FIFO_PIPES == 1);
|
|
struct stat st;
|
|
int fstat_result = fstat (fd, &st);
|
|
|
|
if (fstat_result != 0)
|
|
return fstat_result;
|
|
|
|
/* We want something that succeeds only for pipes, but on
|
|
POSIX-conforming hosts S_ISFIFO succeeds for both FIFOs and pipes
|
|
and we know of no portable, reliable way to distinguish them in
|
|
general. However, in practice pipes always have a link count <=
|
|
PIPE_LINK_COUNT_MAX (unless someone attaches them to the file
|
|
system name space using fattach, in which case they're not really
|
|
pipes any more), so test for that as well.
|
|
|
|
On Darwin 7.7, pipes are sockets, so check for those instead. */
|
|
|
|
if (! ((HAVE_FIFO_PIPES == 0 || HAVE_FIFO_PIPES == 1)
|
|
&& PIPE_LINK_COUNT_MAX != (nlink_t) -1)
|
|
&& (S_ISFIFO (st.st_mode) | S_ISSOCK (st.st_mode)))
|
|
{
|
|
int fd_pair[2];
|
|
int pipe_result = pipe (fd_pair);
|
|
if (pipe_result != 0)
|
|
return pipe_result;
|
|
else
|
|
{
|
|
struct stat pipe_st;
|
|
int fstat_pipe_result = fstat (fd_pair[0], &pipe_st);
|
|
int fstat_pipe_errno = errno;
|
|
close (fd_pair[0]);
|
|
close (fd_pair[1]);
|
|
if (fstat_pipe_result != 0)
|
|
{
|
|
errno = fstat_pipe_errno;
|
|
return fstat_pipe_result;
|
|
}
|
|
check_for_fifo = (S_ISFIFO (pipe_st.st_mode) != 0);
|
|
pipe_link_count_max = pipe_st.st_nlink;
|
|
}
|
|
}
|
|
|
|
return
|
|
(st.st_nlink <= pipe_link_count_max
|
|
&& (check_for_fifo ? S_ISFIFO (st.st_mode) : S_ISSOCK (st.st_mode)));
|
|
}
|
|
|
|
#endif
|