| 1 | /* Adjust a file descriptor result so that it avoids clobbering |
| 2 | STD{IN,OUT,ERR}_FILENO, with specific flags. |
| 3 | |
| 4 | Copyright (C) 2005-2006, 2009-2020 Free Software Foundation, Inc. |
| 5 | |
| 6 | This program is free software: you can redistribute it and/or modify |
| 7 | it under the terms of the GNU General Public License as published by |
| 8 | the Free Software Foundation; either version 3 of the License, or |
| 9 | (at your option) any later version. |
| 10 | |
| 11 | This program is distributed in the hope that it will be useful, |
| 12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 14 | GNU General Public License for more details. |
| 15 | |
| 16 | You should have received a copy of the GNU General Public License |
| 17 | along with this program. If not, see <https://www.gnu.org/licenses/>. */ |
| 18 | |
| 19 | /* Written by Paul Eggert and Eric Blake. */ |
| 20 | |
| 21 | #include <config.h> |
| 22 | |
| 23 | /* Specification. */ |
| 24 | #include "unistd-safer.h" |
| 25 | |
| 26 | #include <errno.h> |
| 27 | #include <unistd.h> |
| 28 | |
| 29 | /* Return FD, unless FD would be a copy of standard input, output, or |
| 30 | error; in that case, return a duplicate of FD, closing FD. If FLAG |
| 31 | contains O_CLOEXEC, the returned FD will have close-on-exec |
| 32 | semantics. On failure to duplicate, close FD, set errno, and |
| 33 | return -1. Preserve errno if FD is negative, so that the caller |
| 34 | can always inspect errno when the returned value is negative. |
| 35 | |
| 36 | This function is usefully wrapped around functions that return file |
| 37 | descriptors, e.g., fd_safer_flag (open ("file", O_RDONLY | flag), flag). */ |
| 38 | |
| 39 | int |
| 40 | fd_safer_flag (int fd, int flag) |
| 41 | { |
| 42 | if (STDIN_FILENO <= fd && fd <= STDERR_FILENO) |
| 43 | { |
| 44 | int f = dup_safer_flag (fd, flag); |
| 45 | int e = errno; |
| 46 | close (fd); |
| 47 | errno = e; |
| 48 | fd = f; |
| 49 | } |
| 50 | |
| 51 | return fd; |
| 52 | } |