1unlink(2)                     System Calls Manual                    unlink(2)
2
3
4

NAME

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

LIBRARY

9       Standard C library (libc, -lc)
10

SYNOPSIS

12       #include <unistd.h>
13
14       int unlink(const char *pathname);
15
16       #include <fcntl.h>           /* Definition of AT_* constants */
17       #include <unistd.h>
18
19       int unlinkat(int dirfd, const char *pathname, int flags);
20
21   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
22
23       unlinkat():
24           Since glibc 2.10:
25               _POSIX_C_SOURCE >= 200809L
26           Before glibc 2.10:
27               _ATFILE_SOURCE
28

DESCRIPTION

30       unlink() deletes a name from the filesystem.  If that name was the last
31       link to a file and no processes have the file open, the file is deleted
32       and the space it was using is made available for reuse.
33
34       If  the  name  was the last link to a file but any processes still have
35       the file open, the file will remain in existence until  the  last  file
36       descriptor referring to it is closed.
37
38       If the name referred to a symbolic link, the link is removed.
39
40       If  the  name referred to a socket, FIFO, or device, the name for it is
41       removed but processes which have the object open may  continue  to  use
42       it.
43
44   unlinkat()
45       The  unlinkat()  system call operates in exactly the same way as either
46       unlink() or rmdir(2) (depending on whether or not  flags  includes  the
47       AT_REMOVEDIR flag) except for the differences described here.
48
49       If  the  pathname given in pathname is relative, then it is interpreted
50       relative to the directory referred to  by  the  file  descriptor  dirfd
51       (rather  than  relative to the current working directory of the calling
52       process, as is done by unlink() and rmdir(2) for a relative pathname).
53
54       If the pathname given in pathname is relative and dirfd is the  special
55       value  AT_FDCWD,  then  pathname is interpreted relative to the current
56       working directory of the calling process (like unlink() and rmdir(2)).
57
58       If the pathname given in pathname is absolute, then dirfd is ignored.
59
60       flags is a bit mask that can either be specified as 0, or by ORing  to‐
61       gether  flag  values  that  control  the operation of unlinkat().  Cur‐
62       rently, only one such flag is defined:
63
64       AT_REMOVEDIR
65              By default, unlinkat() performs the equivalent  of  unlink()  on
66              pathname.   If the AT_REMOVEDIR flag is specified, then performs
67              the equivalent of rmdir(2) on pathname.
68
69       See openat(2) for an explanation of the need for unlinkat().
70

RETURN VALUE

72       On success, zero is returned.  On error, -1 is returned, and  errno  is
73       set to indicate the error.
74

ERRORS

76       EACCES Write access to the directory containing pathname is not allowed
77              for the process's effective UID, or one of  the  directories  in
78              pathname  did not allow search permission.  (See also path_reso‐
79              lution(7).)
80
81       EBUSY  The file pathname cannot be unlinked because it is being used by
82              the  system or another process; for example, it is a mount point
83              or the NFS client software created it to represent an active but
84              otherwise nameless inode ("NFS silly renamed").
85
86       EFAULT pathname points outside your accessible address space.
87
88       EIO    An I/O error occurred.
89
90       EISDIR pathname  refers  to  a directory.  (This is the non-POSIX value
91              returned since Linux 2.1.132.)
92
93       ELOOP  Too many symbolic links were encountered  in  translating  path‐
94              name.
95
96       ENAMETOOLONG
97              pathname was too long.
98
99       ENOENT A component in pathname does not exist or is a dangling symbolic
100              link, or pathname is empty.
101
102       ENOMEM Insufficient kernel memory was available.
103
104       ENOTDIR
105              A component used as a directory in pathname is not, in  fact,  a
106              directory.
107
108       EPERM  The system does not allow unlinking of directories, or unlinking
109              of directories requires  privileges  that  the  calling  process
110              doesn't  have.   (This  is the POSIX prescribed error return; as
111              noted above, Linux returns EISDIR for this case.)
112
113       EPERM (Linux only)
114              The filesystem does not allow unlinking of files.
115
116       EPERM or EACCES
117              The directory containing pathname has the sticky  bit  (S_ISVTX)
118              set  and  the  process's effective UID is neither the UID of the
119              file to be deleted nor that of the directory containing it,  and
120              the  process  is  not  privileged  (Linux:  does  not  have  the
121              CAP_FOWNER capability).
122
123       EPERM  The file to be unlinked  is  marked  immutable  or  append-only.
124              (See ioctl_iflags(2).)
125
126       EROFS  pathname refers to a file on a read-only filesystem.
127
128       The same errors that occur for unlink() and rmdir(2) can also occur for
129       unlinkat().  The following additional errors can occur for unlinkat():
130
131       EBADF  pathname is relative but dirfd is neither AT_FDCWD nor  a  valid
132              file descriptor.
133
134       EINVAL An invalid flag value was specified in flags.
135
136       EISDIR pathname  refers to a directory, and AT_REMOVEDIR was not speci‐
137              fied in flags.
138
139       ENOTDIR
140              pathname is relative and dirfd is a file descriptor referring to
141              a file other than a directory.
142

STANDARDS

144       POSIX.1-2008.
145

HISTORY

147       unlink()
148              SVr4, 4.3BSD, POSIX.1-2001.
149
150       unlinkat()
151              POSIX.1-2008.  Linux 2.6.16, glibc 2.4.
152
153   glibc
154       On  older  kernels  where  unlinkat() is unavailable, the glibc wrapper
155       function falls back to the use of unlink() or rmdir(2).  When  pathname
156       is  a  relative pathname, glibc constructs a pathname based on the sym‐
157       bolic link in /proc/self/fd that corresponds to the dirfd argument.
158

BUGS

160       Infelicities in the protocol underlying NFS can  cause  the  unexpected
161       disappearance of files which are still being used.
162

SEE ALSO

164       rm(1),  unlink(1),  chmod(2),  link(2),  mknod(2),  open(2), rename(2),
165       rmdir(2), mkfifo(3), remove(3), path_resolution(7), symlink(7)
166
167
168
169Linux man-pages 6.04              2023-03-30                         unlink(2)
Impressum