1 UNLINK(2) System Calls UNLINK(2)
2
3
4
5 NAME
6 unlink, unlinkat - remove directory entry
7
8 SYNOPSIS
9 #include <unistd.h>
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11 int unlink(const char *path);
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13
14 int unlinkat(int dirfd, const char *path, int flag);
15
16
17 DESCRIPTION
18 The unlink() function removes a link to a file. If path names a
19 symbolic link, unlink() removes the symbolic link named by path and
20 does not affect any file or directory named by the contents of the
21 symbolic link. Otherwise, unlink() removes the link named by the
22 pathname pointed to by path and decrements the link count of the file
23 referenced by the link.
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25
26 The unlinkat() function also removes a link to a file. See fsattr(5).
27 If the flag argument is 0, the behavior of unlinkat() is the same as
28 unlink() except in the processing of its path argument. If path is
29 absolute, unlinkat() behaves the same as unlink() and the dirfd
30 argument is unused. If path is relative and dirfd has the value
31 AT_FDCWD, defined in <fcntl.h>, unlinkat() also behaves the same as
32 unlink(). Otherwise, path is resolved relative to the directory
33 referenced by the dirfd argument.
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35
36 If the flag argument is set to the value AT_REMOVEDIR, defined in
37 <fcntl.h>, unlinkat() behaves the same as rmdir(2) except in the
38 processing of the path argument as described above.
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40
41 When the file's link count becomes 0 and no process has the file open,
42 the space occupied by the file will be freed and the file is no longer
43 accessible. If one or more processes have the file open when the last
44 link is removed, the link is removed before unlink() or unlinkat()
45 returns, but the removal of the file contents is postponed until all
46 references to the file are closed.
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48
49 If the path argument is a directory and the filesystem supports
50 unlink() and unlinkat() on directories, the directory is unlinked from
51 its parent with no cleanup being performed. In UFS, the disconnected
52 directory will be found the next time the filesystem is checked with
53 fsck(1M). The unlink() and unlinkat() functions will not fail simply
54 because a directory is not empty. The user with appropriate privileges
55 can orphan a non-empty directory without generating an error message.
56
57
58 If the path argument is a directory and the filesystem does not support
59 unlink() and unlink() on directories (for example, ZFS), the call will
60 fail with errno set to EPERM.
61
62
63 Upon successful completion, unlink() and unlinkat() will mark for
64 update the st_ctime and st_mtime fields of the parent directory. If
65 the file's link count is not 0, the st_ctime field of the file will be
66 marked for update.
67
68 RETURN VALUES
69 Upon successful completion, 0 is returned. Otherwise, -1 is returned,
70 errno is set to indicate the error, and the file is not unlinked.
71
72 ERRORS
73 The unlink() and unlinkat() functions will fail if:
74
75 EACCES
76 Search permission is denied for a component of the path
77 prefix, or write permission is denied on the directory
78 containing the link to be removed.
79
80
81 EACCES
82 The parent directory has the sticky bit set and the
83 file is not writable by the user, the user does not own
84 the parent directory, the user does not own the file,
85 and the user is not a privileged user.
86
87
88 EBUSY
89 The entry to be unlinked is the mount point for a
90 mounted file system.
91
92
93 EEXIST
94 The entry to be unlinked is a directory which is not
95 empty.
96
97
98 EFAULT
99 The path argument points to an illegal address.
100
101
102 EILSEQ
103 The path argument includes non-UTF8 characters and the
104 file system accepts only file names where all
105 characters are part of the UTF-8 character codeset.
106
107
108 EINTR
109 A signal was caught during the execution of the
110 unlink() function.
111
112
113 ELOOP
114 Too many symbolic links were encountered in translating
115 path.
116
117
118 ENAMETOOLONG
119 The length of the path argument exceeds PATH_MAX, or
120 the length of a path component exceeds NAME_MAX while
121 _POSIX_NO_TRUNC is in effect.
122
123
124 ENOENT
125 The named file does not exist or is a null pathname.
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127
128 ENOLINK
129 The path argument points to a remote machine and the
130 link to that machine is no longer active.
131
132
133 ENOTDIR
134 A component of the path prefix is not a directory or
135 the provided directory descriptor for unlinkat() is not
136 AT_FDCWD or does not reference a directory.
137
138
139 EPERM
140 The named file is a directory and {PRIV_SYS_LINKDIR} is
141 not asserted in the effective set of the calling
142 process, or the filesystem implementation does not
143 support unlink() or unlinkat() on directories.
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145
146 EROFS
147 The directory entry to be unlinked is part of a read-
148 only file system.
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150
151
152 The unlink() and unlinkat() functions may fail if:
153
154 ENAMETOOLONG
155 Pathname resolution of a symbolic link produced an
156 intermediate result whose length exceeds {PATH_MAX}.
157
158
159 ETXTBSY
160 The entry to be unlinked is the last directory entry to
161 a pure procedure (shared text) file that is being
162 executed.
163
164
165 USAGE
166 Applications should use rmdir(2) to remove a directory.
167
168 ATTRIBUTES
169 See attributes(5) for descriptions of the following attributes:
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171
172
173
174 +--------------------+----------------------------------------------+
175 | ATTRIBUTE TYPE | ATTRIBUTE VALUE |
176 +--------------------+----------------------------------------------+
177 |Interface Stability | unlink() is Standard; unlinkat() is Evolving |
178 +--------------------+----------------------------------------------+
179 |MT-Level | Async-Signal-Safe |
180 +--------------------+----------------------------------------------+
181
182 SEE ALSO
183 rm(1), close(2), link(2), open(2), rmdir(2), remove(3C), attributes(5),
184 privileges(5), fsattr(5)
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187
188 December 7, 2016 UNLINK(2)