1 /* Copyright (C) 1991-2022 Free Software Foundation, Inc. 2 This file is part of the GNU C Library. 3 4 The GNU C Library is free software; you can redistribute it and/or 5 modify it under the terms of the GNU Lesser General Public 6 License as published by the Free Software Foundation; either 7 version 2.1 of the License, or (at your option) any later version. 8 9 The GNU C Library is distributed in the hope that it will be useful, 10 but WITHOUT ANY WARRANTY; without even the implied warranty of 11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 12 Lesser General Public License for more details. 13 14 You should have received a copy of the GNU Lesser General Public 15 License along with the GNU C Library; if not, see 16 <https://www.gnu.org/licenses/>. */ 17 18 #include <errno.h> 19 #include <limits.h> 20 #include <termios.h> 21 #include <stdlib.h> 22 23 #include "ttyname.h" 24 25 static char *ttyname_buf = NULL; 26 libc_freeres_fn(free_mem)27libc_freeres_fn (free_mem) 28 { 29 free (ttyname_buf); 30 } 31 32 /* Return the pathname of the terminal FD is open on, or NULL on errors. 33 The returned storage is good only until the next call to this function. */ 34 char * ttyname(int fd)35ttyname (int fd) 36 { 37 /* isatty check, tcgetattr is used because it sets the correct 38 errno (EBADF resp. ENOTTY) on error. Fast error path to avoid the 39 allocation */ 40 struct termios term; 41 if (__glibc_unlikely (__tcgetattr (fd, &term) < 0)) 42 return NULL; 43 44 if (ttyname_buf == NULL) 45 { 46 ttyname_buf = malloc (PATH_MAX); 47 if (ttyname_buf == NULL) 48 return NULL; 49 } 50 51 int result = __ttyname_r (fd, ttyname_buf, PATH_MAX); 52 if (result != 0) 53 { 54 __set_errno (result); 55 return NULL; 56 } 57 return ttyname_buf; 58 } 59