man2/unlink.2

   1 .\" This manpage is Copyright (C) 1992 Drew Eckhardt;
   2 .\"             and Copyright (C) 1993 Ian Jackson
   3 .\"             and Copyright (C) 2006, 2014 Michael Kerrisk.
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  27 .\" Modified 1993-07-24 by Rik Faith <faith@cs.unc.edu>
  28 .\" Modified 1996-09-08 by Arnt Gulbrandsen <agulbra@troll.no>
  29 .\" Modified 1997-01-31 by Eric S. Raymond <esr@thyrsus.com>
  30 .\" Modified 2001-05-17 by aeb
  31 .\" Modified 2004-06-23 by Michael Kerrisk <mtk.manpages@gmail.com>
  32 .\"
  33 .TH UNLINK 2 2017-09-15 "Linux" "Linux Programmer's Manual"
  34 .SH NAME
  35 unlink, unlinkat \- delete a name and possibly the file it refers to
  36 .SH SYNOPSIS
  37 .nf
  38 .B #include <unistd.h>
  39 .PP
  40 .BI "int unlink(const char *" pathname );
  41
  42 .BR "#include <fcntl.h>           " "/* Definition of AT_* constants */"
  43 .B #include <unistd.h>
  44 .PP
  45 .BI "int unlinkat(int " dirfd ", const char *" pathname ", int " flags );
  46 .fi
  47 .PP
  48 .in -4n
  49 Feature Test Macro Requirements for glibc (see
  50 .BR feature_test_macros (7)):
  51 .in
  52 .PP
  53 .BR unlinkat ():
  54 .PD 0
  55 .ad l
  56 .RS 4
  57 .TP 4
  58 Since glibc 2.10:
  59 _POSIX_C_SOURCE\ >=\ 200809L
  60 .TP
  61 Before glibc 2.10:
  62 _ATFILE_SOURCE
  63 .RE
  64 .ad
  65 .PD
  66 .SH DESCRIPTION
  67 .BR unlink ()
  68 deletes a name from the filesystem.
  69 If that name was the
  70 last link to a file and no processes have the file open, the file is
  71 deleted and the space it was using is made available for reuse.
  72 .PP
  73 If the name was the last link to a file but any processes still have
  74 the file open, the file will remain in existence until the last file
  75 descriptor referring to it is closed.
  76 .PP
  77 If the name referred to a symbolic link, the link is removed.
  78 .PP
  79 If the name referred to a socket, FIFO, or device, the name for it is
  80 removed but processes which have the object open may continue to use
  81 it.
  82 .SS unlinkat()
  83 The
  84 .BR unlinkat ()
  85 system call operates in exactly the same way as either
  86 .BR unlink ()
  87 or
  88 .BR rmdir (2)
  89 (depending on whether or not
  90 .I flags
  91 includes the
  92 .B AT_REMOVEDIR
  93 flag)
  94 except for the differences described here.
  95 .PP
  96 If the pathname given in
  97 .I pathname
  98 is relative, then it is interpreted relative to the directory
  99 referred to by the file descriptor
 100 .I dirfd
 101 (rather than relative to the current working directory of
 102 the calling process, as is done by
 103 .BR unlink ()
 104 and
 105 .BR rmdir (2)
 106 for a relative pathname).
 107 .PP
 108 If the pathname given in
 109 .I pathname
 110 is relative and
 111 .I dirfd
 112 is the special value
 113 .BR AT_FDCWD ,
 114 then
 115 .I pathname
 116 is interpreted relative to the current working
 117 directory of the calling process (like
 118 .BR unlink ()
 119 and
 120 .BR rmdir (2)).
 121 .PP
 122 If the pathname given in
 123 .I pathname
 124 is absolute, then
 125 .I dirfd
 126 is ignored.
 127 .PP
 128 .I flags
 129 is a bit mask that can either be specified as 0, or by ORing
 130 together flag values that control the operation of
 131 .BR unlinkat ().
 132 Currently, only one such flag is defined:
 133 .TP
 134 .B AT_REMOVEDIR
 135 By default,
 136 .BR unlinkat ()
 137 performs the equivalent of
 138 .BR unlink ()
 139 on
 140 .IR pathname .
 141 If the
 142 .B AT_REMOVEDIR
 143 flag is specified, then
 144 performs the equivalent of
 145 .BR rmdir (2)
 146 on
 147 .IR pathname .
 148 .PP
 149 See
 150 .BR openat (2)
 151 for an explanation of the need for
 152 .BR unlinkat ().
 153 .SH RETURN VALUE
 154 On success, zero is returned.
 155 On error, \-1 is returned, and
 156 .I errno
 157 is set appropriately.
 158 .SH ERRORS
 159 .TP
 160 .B EACCES
 161 Write access to the directory containing
 162 .I pathname
 163 is not allowed for the process's effective UID, or one of the
 164 directories in
 165 .I pathname
 166 did not allow search permission.
 167 (See also
 168 .BR path_resolution (7).)
 169 .TP
 170 .BR EBUSY
 171 The file
 172 .I pathname
 173 cannot be unlinked because it is being used by the system
 174 or another process;
 175 for example, it is a mount point
 176 or the NFS client software created it to represent an
 177 active but otherwise nameless inode ("NFS silly renamed").
 178 .TP
 179 .B EFAULT
 180 .I pathname
 181 points outside your accessible address space.
 182 .TP
 183 .B EIO
 184 An I/O error occurred.
 185 .TP
 186 .B EISDIR
 187 .I pathname
 188 refers to a directory.
 189 (This is the non-POSIX value returned by Linux since 2.1.132.)
 190 .TP
 191 .B ELOOP
 192 Too many symbolic links were encountered in translating
 193 .IR pathname .
 194 .TP
 195 .B ENAMETOOLONG
 196 .IR pathname " was too long."
 197 .TP
 198 .B ENOENT
 199 A component in
 200 .I pathname
 201 does not exist or is a dangling symbolic link, or
 202 .I pathname
 203 is empty.
 204 .TP
 205 .B ENOMEM
 206 Insufficient kernel memory was available.
 207 .TP
 208 .B ENOTDIR
 209 A component used as a directory in
 210 .I pathname
 211 is not, in fact, a directory.
 212 .TP
 213 .B EPERM
 214 The system does not allow unlinking of directories,
 215 or unlinking of directories requires privileges that the
 216 calling process doesn't have.
 217 (This is the POSIX prescribed error return;
 218 as noted above, Linux returns
 219 .B EISDIR
 220 for this case.)
 221 .TP
 222 .BR EPERM " (Linux only)"
 223 The filesystem does not allow unlinking of files.
 224 .TP
 225 .BR EPERM " or " EACCES
 226 The directory containing
 227 .I pathname
 228 has the sticky bit
 229 .RB ( S_ISVTX )
 230 set and the process's effective UID is neither the UID of the file to
 231 be deleted nor that of the directory containing it, and
 232 the process is not privileged (Linux: does not have the
 233 .B CAP_FOWNER
 234 capability).
 235 .TP
 236 .B EPERM
 237 The file to be unlinked is marked immutable or append-only.
 238 (See
 239 .BR ioctl_iflags (2).)
 240 .TP
 241 .B EROFS
 242 .I pathname
 243 refers to a file on a read-only filesystem.
 244 .PP
 245 The same errors that occur for
 246 .BR unlink ()
 247 and
 248 .BR rmdir (2)
 249 can also occur for
 250 .BR unlinkat ().
 251 The following additional errors can occur for
 252 .BR unlinkat ():
 253 .TP
 254 .B EBADF
 255 .I dirfd
 256 is not a valid file descriptor.
 257 .TP
 258 .B EINVAL
 259 An invalid flag value was specified in
 260 .IR flags .
 261 .TP
 262 .B EISDIR
 263 .I pathname
 264 refers to a directory, and
 265 .B AT_REMOVEDIR
 266 was not specified in
 267 .IR flags .
 268 .TP
 269 .B ENOTDIR
 270 .I pathname
 271 is relative and
 272 .I dirfd
 273 is a file descriptor referring to a file other than a directory.
 274 .SH VERSIONS
 275 .BR unlinkat ()
 276 was added to Linux in kernel 2.6.16;
 277 library support was added to glibc in version 2.4.
 278 .SH CONFORMING TO
 279 .BR unlink ():
 280 SVr4, 4.3BSD, POSIX.1-2001, POSIX.1-2008.
 281 .\" SVr4 documents additional error
 282 .\" conditions EINTR, EMULTIHOP, ETXTBSY, ENOLINK.
 283 .PP
 284 .BR unlinkat ():
 285 POSIX.1-2008.
 286 .SH NOTES
 287 .SS Glibc notes
 288 On older kernels where
 289 .BR unlinkat ()
 290 is unavailable, the glibc wrapper function falls back to the use of
 291 .BR unlink ()
 292 or
 293 .BR rmdir (2).
 294 When
 295 .I pathname
 296 is a relative pathname,
 297 glibc constructs a pathname based on the symbolic link in
 298 .IR /proc/self/fd
 299 that corresponds to the
 300 .IR dirfd
 301 argument.
 302 .SH BUGS
 303 Infelicities in the protocol underlying NFS can cause the unexpected
 304 disappearance of files which are still being used.
 305 .SH SEE ALSO
 306 .BR rm (1),
 307 .BR unlink (1),
 308 .BR chmod (2),
 309 .BR link (2),
 310 .BR mknod (2),
 311 .BR open (2),
 312 .BR rename (2),
 313 .BR rmdir (2),
 314 .BR mkfifo (3),
 315 .BR remove (3),
 316 .BR path_resolution (7),
 317 .BR symlink (7)