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 <stddef.h>
21#include <dirent.h>
22#include <sys/types.h>
23#include <sys/stat.h>
24#include <unistd.h>
25#include <string.h>
26#include <stdlib.h>
27
28char *__ttyname;
29
30static char *getttyname (int fd, dev_t mydev, ino_t myino,
31 int save, int *dostat);
32
33
34libc_freeres_ptr (static char *getttyname_name);
35
36static char *
37getttyname (int fd, dev_t mydev, ino_t myino, int save, int *dostat)
38{
39 static const char dev[] = "/dev";
40 static size_t namelen;
41 struct stat st;
42 DIR *dirstream;
43 struct dirent *d;
44
45 dirstream = __opendir (dev);
46 if (dirstream == NULL)
47 {
48 *dostat = -1;
49 return NULL;
50 }
51
52 while ((d = __readdir (dirstream)) != NULL)
53 if (((ino_t) d->d_fileno == myino || *dostat)
54 && strcmp (d->d_name, "stdin")
55 && strcmp (d->d_name, "stdout")
56 && strcmp (d->d_name, "stderr"))
57 {
58 size_t dlen = _D_ALLOC_NAMLEN (d);
59 if (sizeof (dev) + dlen > namelen)
60 {
61 free (getttyname_name);
62 namelen = 2 * (sizeof (dev) + dlen); /* Big enough. */
63 getttyname_name = malloc (namelen);
64 if (! getttyname_name)
65 {
66 *dostat = -1;
67 /* Perhaps it helps to free the directory stream buffer. */
68 (void) __closedir (dirstream);
69 return NULL;
70 }
71 *((char *) __mempcpy (getttyname_name, dev, sizeof (dev) - 1))
72 = '/';
73 }
74 (void) __mempcpy (&getttyname_name[sizeof (dev)], d->d_name, dlen);
75 if (stat (getttyname_name, &st) == 0
76#ifdef _STATBUF_ST_RDEV
77 && S_ISCHR (st.st_mode) && st.st_rdev == mydev
78#else
79 && (ino_t) d->d_fileno == myino && st.st_dev == mydev
80#endif
81 )
82 {
83 (void) __closedir (dirstream);
84 __ttyname = getttyname_name;
85 __set_errno (save);
86 return getttyname_name;
87 }
88 }
89
90 (void) __closedir (dirstream);
91 __set_errno (save);
92 return NULL;
93}
94
95/* Return the pathname of the terminal FD is open on, or NULL on errors.
96 The returned storage is good only until the next call to this function. */
97char *
98ttyname (int fd)
99{
100 struct stat st;
101 int dostat = 0;
102 char *name;
103 int save = errno;
104
105 if (!__isatty (fd))
106 return NULL;
107
108 if (fstat (fd, &st) < 0)
109 return NULL;
110
111#ifdef _STATBUF_ST_RDEV
112 name = getttyname (fd, st.st_rdev, st.st_ino, save, &dostat);
113#else
114 name = getttyname (fd, st.st_dev, st.st_ino, save, &dostat);
115#endif
116
117 if (!name && dostat != -1)
118 {
119 dostat = 1;
120#ifdef _STATBUF_ST_RDEV
121 name = getttyname (fd, st.st_rdev, st.st_ino, save, &dostat);
122#else
123 name = getttyname (fd, st.st_dev, st.st_ino, save, &dostat);
124#endif
125 }
126
127 return name;
128}
129

source code of glibc/sysdeps/posix/ttyname.c