1/* Copyright (C) 1991-2024 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#include <set-freeres.h>
28
29char *__ttyname;
30
31static char *getttyname (int fd, dev_t mydev, ino_t myino,
32 int save, int *dostat);
33
34
35static char *getttyname_name;
36weak_alias (getttyname_name, __ttyname_freemem_ptr)
37
38static char *
39getttyname (int fd, dev_t mydev, ino_t myino, int save, int *dostat)
40{
41 static const char dev[] = "/dev";
42 static size_t namelen;
43 struct stat st;
44 DIR *dirstream;
45 struct dirent *d;
46
47 dirstream = __opendir (name: dev);
48 if (dirstream == NULL)
49 {
50 *dostat = -1;
51 return NULL;
52 }
53
54 while ((d = __readdir (dirp: dirstream)) != NULL)
55 if (((ino_t) d->d_fileno == myino || *dostat)
56 && strcmp (d->d_name, "stdin")
57 && strcmp (d->d_name, "stdout")
58 && strcmp (d->d_name, "stderr"))
59 {
60 size_t dlen = _D_ALLOC_NAMLEN (d);
61 if (sizeof (dev) + dlen > namelen)
62 {
63 free (ptr: getttyname_name);
64 namelen = 2 * (sizeof (dev) + dlen); /* Big enough. */
65 getttyname_name = malloc (size: namelen);
66 if (! getttyname_name)
67 {
68 *dostat = -1;
69 /* Perhaps it helps to free the directory stream buffer. */
70 (void) __closedir (dirp: dirstream);
71 return NULL;
72 }
73 *((char *) __mempcpy (getttyname_name, dev, sizeof (dev) - 1))
74 = '/';
75 }
76 (void) __mempcpy (&getttyname_name[sizeof (dev)], d->d_name, dlen);
77 if (stat (file: getttyname_name, buf: &st) == 0
78#ifdef _STATBUF_ST_RDEV
79 && S_ISCHR (st.st_mode) && st.st_rdev == mydev
80#else
81 && (ino_t) d->d_fileno == myino && st.st_dev == mydev
82#endif
83 )
84 {
85 (void) __closedir (dirp: dirstream);
86 __ttyname = getttyname_name;
87 __set_errno (save);
88 return getttyname_name;
89 }
90 }
91
92 (void) __closedir (dirp: dirstream);
93 __set_errno (save);
94 return NULL;
95}
96
97/* Return the pathname of the terminal FD is open on, or NULL on errors.
98 The returned storage is good only until the next call to this function. */
99char *
100ttyname (int fd)
101{
102 struct stat st;
103 int dostat = 0;
104 char *name;
105 int save = errno;
106
107 if (!__isatty (fd: fd))
108 return NULL;
109
110 if (fstat (fd: fd, buf: &st) < 0)
111 return NULL;
112
113#ifdef _STATBUF_ST_RDEV
114 name = getttyname (fd, mydev: st.st_rdev, myino: st.st_ino, save, dostat: &dostat);
115#else
116 name = getttyname (fd, st.st_dev, st.st_ino, save, &dostat);
117#endif
118
119 if (!name && dostat != -1)
120 {
121 dostat = 1;
122#ifdef _STATBUF_ST_RDEV
123 name = getttyname (fd, mydev: st.st_rdev, myino: st.st_ino, save, dostat: &dostat);
124#else
125 name = getttyname (fd, st.st_dev, st.st_ino, save, &dostat);
126#endif
127 }
128
129 return name;
130}
131

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