1UNLINK(2)                  Linux Programmer's Manual                 UNLINK(2)
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NAME

6       unlink, unlinkat - delete a name and possibly the file it refers to
7

SYNOPSIS

9       #include <unistd.h>
10
11       int unlink(const char *pathname);
12
13       #include <fcntl.h>           /* Definition of AT_* constants */
14       #include <unistd.h>
15
16       int unlinkat(int dirfd, const char *pathname, int flags);
17
18   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
19
20       unlinkat():
21           Since glibc 2.10:
22               _POSIX_C_SOURCE >= 200809L
23           Before glibc 2.10:
24               _ATFILE_SOURCE
25

DESCRIPTION

27       unlink() deletes a name from the filesystem.  If that name was the last
28       link to a file and no processes have the file open, the file is deleted
29       and the space it was using is made available for reuse.
30
31       If  the  name  was the last link to a file but any processes still have
32       the file open, the file will remain in existence until  the  last  file
33       descriptor referring to it is closed.
34
35       If the name referred to a symbolic link, the link is removed.
36
37       If  the  name referred to a socket, FIFO, or device, the name for it is
38       removed but processes which have the object open may  continue  to  use
39       it.
40
41   unlinkat()
42       The  unlinkat()  system call operates in exactly the same way as either
43       unlink() or rmdir(2) (depending on whether or not  flags  includes  the
44       AT_REMOVEDIR flag) except for the differences described here.
45
46       If  the  pathname given in pathname is relative, then it is interpreted
47       relative to the directory referred to  by  the  file  descriptor  dirfd
48       (rather  than  relative to the current working directory of the calling
49       process, as is done by unlink() and rmdir(2) for a relative pathname).
50
51       If the pathname given in pathname is relative and dirfd is the  special
52       value  AT_FDCWD,  then  pathname is interpreted relative to the current
53       working directory of the calling process (like unlink() and rmdir(2)).
54
55       If the pathname given in pathname is absolute, then dirfd is ignored.
56
57       flags is a bit mask that can either be specified  as  0,  or  by  ORing
58       together  flag  values  that control the operation of unlinkat().  Cur‐
59       rently, only one such flag is defined:
60
61       AT_REMOVEDIR
62              By default, unlinkat() performs the equivalent  of  unlink()  on
63              pathname.   If the AT_REMOVEDIR flag is specified, then performs
64              the equivalent of rmdir(2) on pathname.
65
66       See openat(2) for an explanation of the need for unlinkat().
67

RETURN VALUE

69       On success, zero is returned.  On error, -1 is returned, and  errno  is
70       set appropriately.
71

ERRORS

73       EACCES Write access to the directory containing pathname is not allowed
74              for the process's effective UID, or one of  the  directories  in
75              pathname  did not allow search permission.  (See also path_reso‐
76              lution(7).)
77
78       EBUSY  The file pathname cannot be unlinked because it is being used by
79              the  system or another process; for example, it is a mount point
80              or the NFS client software created it to represent an active but
81              otherwise nameless inode ("NFS silly renamed").
82
83       EFAULT pathname points outside your accessible address space.
84
85       EIO    An I/O error occurred.
86
87       EISDIR pathname  refers  to  a directory.  (This is the non-POSIX value
88              returned by Linux since 2.1.132.)
89
90       ELOOP  Too many symbolic links were encountered  in  translating  path‐
91              name.
92
93       ENAMETOOLONG
94              pathname was too long.
95
96       ENOENT A component in pathname does not exist or is a dangling symbolic
97              link, or pathname is empty.
98
99       ENOMEM Insufficient kernel memory was available.
100
101       ENOTDIR
102              A component used as a directory in pathname is not, in  fact,  a
103              directory.
104
105       EPERM  The system does not allow unlinking of directories, or unlinking
106              of directories requires  privileges  that  the  calling  process
107              doesn't  have.   (This  is the POSIX prescribed error return; as
108              noted above, Linux returns EISDIR for this case.)
109
110       EPERM (Linux only)
111              The filesystem does not allow unlinking of files.
112
113       EPERM or EACCES
114              The directory containing pathname has the sticky  bit  (S_ISVTX)
115              set  and  the  process's effective UID is neither the UID of the
116              file to be deleted nor that of the directory containing it,  and
117              the  process  is  not  privileged  (Linux:  does  not  have  the
118              CAP_FOWNER capability).
119
120       EPERM  The file to be unlinked  is  marked  immutable  or  append-only.
121              (See ioctl_iflags(2).)
122
123       EROFS  pathname refers to a file on a read-only filesystem.
124
125       The same errors that occur for unlink() and rmdir(2) can also occur for
126       unlinkat().  The following additional errors can occur for unlinkat():
127
128       EBADF  dirfd is not a valid file descriptor.
129
130       EINVAL An invalid flag value was specified in flags.
131
132       EISDIR pathname refers to a directory, and AT_REMOVEDIR was not  speci‐
133              fied in flags.
134
135       ENOTDIR
136              pathname is relative and dirfd is a file descriptor referring to
137              a file other than a directory.
138

VERSIONS

140       unlinkat() was added to Linux in kernel  2.6.16;  library  support  was
141       added to glibc in version 2.4.
142

CONFORMING TO

144       unlink(): SVr4, 4.3BSD, POSIX.1-2001, POSIX.1-2008.
145
146       unlinkat(): POSIX.1-2008.
147

NOTES

149   Glibc notes
150       On  older  kernels  where  unlinkat() is unavailable, the glibc wrapper
151       function falls back to the use of unlink() or rmdir(2).  When  pathname
152       is  a  relative pathname, glibc constructs a pathname based on the sym‐
153       bolic link in /proc/self/fd that corresponds to the dirfd argument.
154

BUGS

156       Infelicities in the protocol underlying NFS can  cause  the  unexpected
157       disappearance of files which are still being used.
158

SEE ALSO

160       rm(1),  unlink(1),  chmod(2),  link(2),  mknod(2),  open(2), rename(2),
161       rmdir(2), mkfifo(3), remove(3), path_resolution(7), symlink(7)
162

COLOPHON

164       This page is part of release 5.07 of the Linux  man-pages  project.   A
165       description  of  the project, information about reporting bugs, and the
166       latest    version    of    this    page,    can     be     found     at
167       https://www.kernel.org/doc/man-pages/.
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171Linux                             2017-09-15                         UNLINK(2)
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