1SYMLINK(3P) POSIX Programmer's Manual SYMLINK(3P)
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6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
13 symlink, symlinkat — make a symbolic link relative to directory file
14 descriptor
15
17 #include <unistd.h>
18 int symlink(const char *path1, const char *path2);
20 int symlinkat(const char *path1, int fd, const char *path2);
21
23 The symlink() function shall create a symbolic link called path2 that
24 contains the string pointed to by path1 (path2 is the name of the sym‐
25 bolic link created, path1 is the string contained in the symbolic
26 link).
27 The string pointed to by path1 shall be treated only as a character
29 string and shall not be validated as a pathname.
30 If the symlink() function fails for any reason other than [EIO], any
32 file named by path2 shall be unaffected.
33 If path2 names a symbolic link, symlink() shall fail and set errno to
35 [EEXIST].
36 The symbolic link's user ID shall be set to the process' effective user
38 ID. The symbolic link's group ID shall be set to the group ID of the
39 parent directory or to the effective group ID of the process. Implemen‐
40 tations shall provide a way to initialize the symbolic link's group ID
41 to the group ID of the parent directory. Implementations may, but need
42 not, provide an implementation-defined way to initialize the symbolic
43 link's group ID to the effective group ID of the calling process.
44 The values of the file mode bits for the created symbolic link are
46 unspecified. All interfaces specified by POSIX.1‐2008 shall behave as
47 if the contents of symbolic links can always be read, except that the
48 value of the file mode bits returned in the st_mode field of the stat
49 structure is unspecified.
50 Upon successful completion, symlink() shall mark for update the last
52 data access, last data modification, and last file status change time‐
53 stamps of the symbolic link. Also, the last data modification and last
54 file status change timestamps of the directory that contains the new
55 entry shall be marked for update.
56 The symlinkat() function shall be equivalent to the symlink() function
58 except in the case where path2 specifies a relative path. In this case
59 the symbolic link is created relative to the directory associated with
60 the file descriptor fd instead of the current working directory. If the
61 file descriptor was opened without O_SEARCH, the function shall check
62 whether directory searches are permitted using the current permissions
63 of the directory underlying the file descriptor. If the file descriptor
64 was opened with O_SEARCH, the function shall not perform the check.
65 If symlinkat() is passed the special value AT_FDCWD in the fd parame‐
67 ter, the current working directory shall be used and the behavior shall
68 be identical to a call to symlink().
69
71 Upon successful completion, these functions shall return 0. Otherwise,
72 these functions shall return −1 and set errno to indicate the error.
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75 These functions shall fail if:
76 EACCES Write permission is denied in the directory where the symbolic
78 link is being created, or search permission is denied for a com‐
79 ponent of the path prefix of path2.
80 EEXIST The path2 argument names an existing file.
82 EIO An I/O error occurs while reading from or writing to the file
84 system.
85 ELOOP A loop exists in symbolic links encountered during resolution of
87 the path2 argument.
88 ENAMETOOLONG
90 The length of a component of the pathname specified by the path2
91 argument is longer than {NAME_MAX} or the length of the path1
92 argument is longer than {SYMLINK_MAX}.
93 ENOENT A component of the path prefix of path2 does not name an exist‐
95 ing file or path2 is an empty string.
96 ENOSPC The directory in which the entry for the new symbolic link is
98 being placed cannot be extended because no space is left on the
99 file system containing the directory, or the new symbolic link
100 cannot be created because no space is left on the file system
101 which shall contain the link, or the file system is out of file-
102 allocation resources.
103 ENOTDIR
105 A component of the path prefix of path2 names an existing file
106 that is neither a directory nor a symbolic link to a directory.
107 EROFS The new symbolic link would reside on a read-only file system.
109 The symlinkat() function shall fail if:
111 EACCES fd was not opened with O_SEARCH and the permissions of the
113 directory underlying fd do not permit directory searches.
114 EBADF The path2 argument does not specify an absolute path and the fd
116 argument is neither AT_FDCWD nor a valid file descriptor open
117 for reading or searching.
118 ENOTDIR
120 The path2 argument is not an absolute path and fd is a file
121 descriptor associated with a non-directory file.
122 These functions may fail if:
124 ELOOP More than {SYMLOOP_MAX} symbolic links were encountered during
126 resolution of the path2 argument.
127 ENAMETOOLONG
129 The length of the path2 argument exceeds {PATH_MAX} or pathname
130 resolution of a symbolic link in the path2 argument produced an
131 intermediate result with a length that exceeds {PATH_MAX}.
132 The following sections are informative.
134
136 None.
137
139 Like a hard link, a symbolic link allows a file to have multiple logi‐
140 cal names. The presence of a hard link guarantees the existence of a
141 file, even after the original name has been removed. A symbolic link
142 provides no such assurance; in fact, the file named by the path1 argu‐
143 ment need not exist when the link is created. A symbolic link can cross
144 file system boundaries.
145 Normal permission checks are made on each component of the symbolic
147 link pathname during its resolution.
148
150 The purpose of the symlinkat() function is to create symbolic links in
151 directories other than the current working directory without exposure
152 to race conditions. Any part of the path of a file could be changed in
153 parallel to a call to symlink(), resulting in unspecified behavior. By
154 opening a file descriptor for the target directory and using the sym‐
155 linkat() function it can be guaranteed that the created symbolic link
156 is located relative to the desired directory.
157
159 None.
160
162 fdopendir(), fstatat(), lchown(), link(), open(), readlink(), rename(),
163 unlink()
164 The Base Definitions volume of POSIX.1‐2008, <unistd.h>
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168 Portions of this text are reprinted and reproduced in electronic form
169 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
170 -- Portable Operating System Interface (POSIX), The Open Group Base
171 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
172 cal and Electronics Engineers, Inc and The Open Group. (This is
173 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
174 event of any discrepancy between this version and the original IEEE and
175 The Open Group Standard, the original IEEE and The Open Group Standard
176 is the referee document. The original Standard can be obtained online
177 at http://www.unix.org/online.html .
178 Any typographical or formatting errors that appear in this page are
180 most likely to have been introduced during the conversion of the source
181 files to man page format. To report such errors, see https://www.ker‐
182 nel.org/doc/man-pages/reporting_bugs.html .
183IEEE/The Open Group 2013 SYMLINK(3P)