| /* 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 |