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13 .TH UNLINK 2 "Dec 7, 2016"
14 .SH NAME
15 unlink, unlinkat \- remove directory entry
16 .SH SYNOPSIS
17 .LP
18 .nf
19 #include <unistd.h>
20
21 \fBint\fR \fBunlink\fR(\fBconst char *\fR\fIpath\fR);
22 .fi
23
24 .LP
25 .nf
26 \fBint\fR \fBunlinkat\fR(\fBint\fR \fIdirfd\fR, \fBconst char *\fR\fIpath\fR, \fBint\fR \fIflag\fR);
27 .fi
28
29 .SH DESCRIPTION
30 .sp
31 .LP
32 The \fBunlink()\fR function removes a link to a file. If \fIpath\fR names a
33 symbolic link, \fBunlink()\fR removes the symbolic link named by \fIpath\fR and
34 does not affect any file or directory named by the contents of the symbolic
35 link. Otherwise, \fBunlink()\fR removes the link named by the pathname pointed
36 to by \fIpath\fR and decrements the link count of the file referenced by the
37 link.
38 .sp
39 .LP
40 The \fBunlinkat()\fR function also removes a link to a file. See
41 \fBfsattr\fR(5). If the \fIflag\fR argument is 0, the behavior of
42 \fBunlinkat()\fR is the same as \fBunlink()\fR except in the processing of its
43 \fIpath\fR argument. If \fIpath\fR is absolute, \fBunlinkat()\fR behaves the
44 same as \fBunlink()\fR and the \fIdirfd\fR argument is unused. If \fIpath\fR is
45 relative and \fIdirfd\fR has the value \fBAT_FDCWD\fR, defined in
46 <\fBfcntl.h\fR>, \fBunlinkat()\fR also behaves the same as \fBunlink()\fR.
47 Otherwise, \fIpath\fR is resolved relative to the directory referenced by the
48 \fIdirfd\fR argument.
49 .sp
50 .LP
51 If the \fIflag\fR argument is set to the value \fBAT_REMOVEDIR\fR, defined in
52 <\fBfcntl.h\fR>, \fBunlinkat()\fR behaves the same as \fBrmdir\fR(2) except in
53 the processing of the \fIpath\fR argument as described above.
54 .sp
55 .LP
56 When the file's link count becomes 0 and no process has the file open, the
57 space occupied by the file will be freed and the file is no longer accessible.
58 If one or more processes have the file open when the last link is removed, the
59 link is removed before \fBunlink()\fR or \fBunlinkat()\fR returns, but the
60 removal of the file contents is postponed until all references to the file are
61 closed.
62 .sp
63 .LP
64 If the \fIpath\fR argument is a directory and the filesystem supports
65 \fBunlink()\fR and \fBunlinkat()\fR on directories, the directory is unlinked
66 from its parent with no cleanup being performed. In UFS, the disconnected
67 directory will be found the next time the filesystem is checked with
68 \fBfsck\fR(1M). The \fBunlink()\fR and \fBunlinkat()\fR functions will not fail
69 simply because a directory is not empty. The user with appropriate privileges
70 can orphan a non-empty directory without generating an error message.
71 .sp
72 .LP
73 If the \fIpath\fR argument is a directory and the filesystem does not support
74 \fBunlink()\fR and \fBunlink()\fR on directories (for example, ZFS), the call
75 will fail with \fBerrno\fR set to \fBEPERM\fR.
76 .sp
77 .LP
78 Upon successful completion, \fBunlink()\fR and \fBunlinkat()\fR will mark for
79 update the \fBst_ctime\fR and \fBst_mtime\fR fields of the parent directory.
80 If the file's link count is not 0, the \fBst_ctime\fR field of the file will be
81 marked for update.
82 .SH RETURN VALUES
83 .sp
84 .LP
85 Upon successful completion, \fB0\fR is returned. Otherwise, \fB\(mi1\fR is
86 returned, \fBerrno\fR is set to indicate the error, and the file is not
87 unlinked.
88 .SH ERRORS
89 .sp
90 .LP
91 The \fBunlink()\fR and \fBunlinkat()\fR functions will fail if:
92 .sp
93 .ne 2
94 .na
95 \fB\fBEACCES\fR\fR
96 .ad
97 .RS 16n
98 Search permission is denied for a component of the \fIpath\fR prefix, or write
99 permission is denied on the directory containing the link to be removed.
100 .RE
101
102 .sp
103 .ne 2
104 .na
105 \fB\fBEACCES\fR\fR
106 .ad
107 .RS 16n
108 The parent directory has the sticky bit set and the file is not writable by the
109 user, the user does not own the parent directory, the user does not own the
110 file, and the user is not a privileged user.
111 .RE
112
113 .sp
114 .ne 2
115 .na
116 \fB\fBEBUSY\fR\fR
117 .ad
118 .RS 16n
119 The entry to be unlinked is the mount point for a mounted file system.
120 .RE
121
122 .sp
123 .ne 2
124 .na
125 \fB\fBEEXIST\fR\fR
126 .ad
127 .RS 16n
128 The entry to be unlinked is a directory which is not empty.
129 .RE
130
131 .sp
132 .ne 2
133 .na
134 \fB\fBEFAULT\fR\fR
135 .ad
136 .RS 16n
137 The \fIpath\fR argument points to an illegal address.
138 .RE
139
140 .sp
141 .ne 2
142 .na
143 \fB\fBEILSEQ\fR\fR
144 .ad
145 .RS 16n
146 The path argument includes non-UTF8 characters and the file system accepts only
147 file names where all characters are part of the UTF-8 character codeset.
148 .RE
149
150 .sp
151 .ne 2
152 .na
153 \fB\fBEINTR\fR\fR
154 .ad
155 .RS 16n
156 A signal was caught during the execution of the \fBunlink()\fR function.
157 .RE
158
159 .sp
160 .ne 2
161 .na
162 \fB\fBELOOP\fR\fR
163 .ad
164 .RS 16n
165 Too many symbolic links were encountered in translating \fIpath\fR.
166 .RE
167
168 .sp
169 .ne 2
170 .na
171 \fB\fBENAMETOOLONG\fR\fR
172 .ad
173 .RS 16n
174 The length of the \fIpath\fR argument exceeds \fBPATH_MAX\fR, or the length of
175 a \fIpath\fR component exceeds \fBNAME_MAX\fR while \fB_POSIX_NO_TRUNC\fR is in
176 effect.
177 .RE
178
179 .sp
180 .ne 2
181 .na
182 \fB\fBENOENT\fR\fR
183 .ad
184 .RS 16n
185 The named file does not exist or is a null pathname.
186 .RE
187
188 .sp
189 .ne 2
190 .na
191 \fB\fBENOLINK\fR\fR
192 .ad
193 .RS 16n
194 The \fIpath\fR argument points to a remote machine and the link to that machine
195 is no longer active.
196 .RE
197
198 .sp
199 .ne 2
200 .na
201 \fB\fBENOTDIR\fR\fR
202 .ad
203 .RS 16n
204 A component of the \fIpath\fR prefix is not a directory or the provided
205 directory descriptor for \fBunlinkat()\fR is not \fBAT_FDCWD\fR or does not
206 reference a directory.
207 .RE
208
209 .sp
210 .ne 2
211 .na
212 \fB\fBEPERM\fR\fR
213 .ad
214 .RS 16n
215 The named file is a directory and {\fBPRIV_SYS_LINKDIR\fR} is not asserted in
216 the effective set of the calling process, or the filesystem implementation does
217 not support \fBunlink()\fR or \fBunlinkat()\fR on directories.
218 .RE
219
220 .sp
221 .ne 2
222 .na
223 \fB\fBEROFS\fR\fR
224 .ad
225 .RS 16n
226 The directory entry to be unlinked is part of a read-only file system.
227 .RE
228
229 .sp
230 .LP
231 The \fBunlink()\fR and \fBunlinkat()\fR functions may fail if:
232 .sp
233 .ne 2
234 .na
235 \fB\fBENAMETOOLONG\fR\fR
236 .ad
237 .RS 16n
238 Pathname resolution of a symbolic link produced an intermediate result whose
239 length exceeds {\fBPATH_MAX\fR}.
240 .RE
241
242 .sp
243 .ne 2
244 .na
245 \fB\fBETXTBSY\fR\fR
246 .ad
247 .RS 16n
248 The entry to be unlinked is the last directory entry to a pure procedure
249 (shared text) file that is being executed.
250 .RE
251
252 .SH USAGE
253 .sp
254 .LP
255 Applications should use \fBrmdir\fR(2) to remove a directory.
256 .SH ATTRIBUTES
257 .sp
258 .LP
259 See \fBattributes\fR(5) for descriptions of the following attributes:
260 .sp
261
262 .sp
263 .TS
264 box;
265 c | c
266 l | l .
267 ATTRIBUTE TYPE ATTRIBUTE VALUE
268 _
269 Interface Stability T{
270 \fBunlink()\fR is Standard; \fBunlinkat()\fR is Evolving
271 T}
272 _
273 MT-Level Async-Signal-Safe
274 .TE
275
276 .SH SEE ALSO
277 .sp
278 .LP
279 \fBrm\fR(1), \fBclose\fR(2), \fBlink\fR(2), \fBopen\fR(2), \fBrmdir\fR(2),
280 \fBremove\fR(3C), \fBattributes\fR(5), \fBprivileges\fR(5), \fBfsattr\fR(5)