man2/symlink.2

   1 .\" This manpage is Copyright (C) 1992 Drew Eckhardt;
   2 .\"             and Copyright (C) 1993 Michael Haardt, Ian Jackson.
   3 .\"             and Copyright (C) 2006, 2014 Michael Kerrisk
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  27 .\" Modified 1993-07-24 by Rik Faith
  28 .\" Modified 1996-04-26 by Nick Duffek <nsd@bbc.com>
  29 .\" Modified 1996-11-06 by Eric S. Raymond <esr@thyrsus.com>
  30 .\" Modified 1997-01-31 by Eric S. Raymond <esr@thyrsus.com>
  31 .\" Modified 2004-06-23 by Michael Kerrisk <mtk.manpages@gmail.com>
  32 .\"
  33 .TH SYMLINK 2 2015-04-19 "Linux" "Linux Programmer's Manual"
  34 .SH NAME
  35 symlink, symlinkat \- make a new name for a file
  36 .SH SYNOPSIS
  37 .nf
  38 .B #include <unistd.h>
  39 .sp
  40 .BI "int symlink(const char *" target ", const char *" linkpath );
  41 .sp
  42 .BR "#include <fcntl.h>           " "/* Definition of AT_* constants */"
  43 .B #include <unistd.h>
  44 .sp
  45 .BI "int symlinkat(const char *" target ", int " newdirfd \
  46 ", const char *" linkpath );
  47 .sp
  48 .fi
  49 .in -4n
  50 Feature Test Macro Requirements for glibc (see
  51 .BR feature_test_macros (7)):
  52 .in
  53 .sp
  54 .ad l
  55 .BR symlink ():
  56 .RS 4
  57 _BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500 ||
  58 _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED || _POSIX_C_SOURCE\ >=\ 200112L
  59 .RE
  60 .sp
  61 .BR symlinkat ():
  62 .PD 0
  63 .ad l
  64 .RS 4
  65 .TP 4
  66 Since glibc 2.10:
  67 _XOPEN_SOURCE\ >=\ 700 || _POSIX_C_SOURCE\ >=\ 200809L
  68 .TP
  69 Before glibc 2.10:
  70 _ATFILE_SOURCE
  71 .RE
  72 .ad b
  73 .PD
  74 .SH DESCRIPTION
  75 .BR symlink ()
  76 creates a symbolic link named
  77 .I linkpath
  78 which contains the string
  79 .IR target .
  80
  81 Symbolic links are interpreted at run time as if the contents of the
  82 link had been substituted into the path being followed to find a file or
  83 directory.
  84
  85 Symbolic links may contain
  86 .I ..
  87 path components, which (if used at the start of the link) refer to the
  88 parent directories of that in which the link resides.
  89
  90 A symbolic link (also known as a soft link) may point to an existing
  91 file or to a nonexistent one; the latter case is known as a dangling
  92 link.
  93
  94 The permissions of a symbolic link are irrelevant; the ownership is
  95 ignored when following the link, but is checked when removal or
  96 renaming of the link is requested and the link is in a directory with
  97 the sticky bit
  98 .RB ( S_ISVTX )
  99 set.
 100
 101 If
 102 .I linkpath
 103 exists, it will
 104 .I not
 105 be overwritten.
 106 .SS symlinkat()
 107 The
 108 .BR symlinkat ()
 109 system call operates in exactly the same way as
 110 .BR symlink (),
 111 except for the differences described here.
 112
 113 If the pathname given in
 114 .I linkpath
 115 is relative, then it is interpreted relative to the directory
 116 referred to by the file descriptor
 117 .I newdirfd
 118 (rather than relative to the current working directory of
 119 the calling process, as is done by
 120 .BR symlink ()
 121 for a relative pathname).
 122
 123 If
 124 .I linkpath
 125 is relative and
 126 .I newdirfd
 127 is the special value
 128 .BR AT_FDCWD ,
 129 then
 130 .I linkpath
 131 is interpreted relative to the current working
 132 directory of the calling process (like
 133 .BR symlink ()).
 134
 135 If
 136 .I linkpath
 137 is absolute, then
 138 .I newdirfd
 139 is ignored.
 140 .SH RETURN VALUE
 141 On success, zero is returned.
 142 On error, \-1 is returned, and
 143 .I errno
 144 is set appropriately.
 145 .SH ERRORS
 146 .TP
 147 .B EACCES
 148 Write access to the directory containing
 149 .I linkpath
 150 is denied, or one of the directories in the path prefix of
 151 .I linkpath
 152 did not allow search permission.
 153 (See also
 154 .BR path_resolution (7).)
 155 .TP
 156 .B EDQUOT
 157 The user's quota of resources on the filesystem has been exhausted.
 158 The resources could be inodes or disk blocks, depending on the filesystem
 159 implementation.
 160 .TP
 161 .B EEXIST
 162 .I linkpath
 163 already exists.
 164 .TP
 165 .B EFAULT
 166 .IR target " or " linkpath " points outside your accessible address space."
 167 .TP
 168 .B EIO
 169 An I/O error occurred.
 170 .TP
 171 .B ELOOP
 172 Too many symbolic links were encountered in resolving
 173 .IR linkpath .
 174 .TP
 175 .B ENAMETOOLONG
 176 .IR target " or " linkpath " was too long."
 177 .TP
 178 .B ENOENT
 179 A directory component in
 180 .I linkpath
 181 does not exist or is a dangling symbolic link, or
 182 .I target
 183 or
 184 .I linkpath
 185 is an empty string.
 186 .TP
 187 .B ENOMEM
 188 Insufficient kernel memory was available.
 189 .TP
 190 .B ENOSPC
 191 The device containing the file has no room for the new directory
 192 entry.
 193 .TP
 194 .B ENOTDIR
 195 A component used as a directory in
 196 .I linkpath
 197 is not, in fact, a directory.
 198 .TP
 199 .B EPERM
 200 The filesystem containing
 201 .I linkpath
 202 does not support the creation of symbolic links.
 203 .TP
 204 .B EROFS
 205 .I linkpath
 206 is on a read-only filesystem.
 207 .PP
 208 The following additional errors can occur for
 209 .BR symlinkat ():
 210 .TP
 211 .B EBADF
 212 .I newdirfd
 213 is not a valid file descriptor.
 214 .TP
 215 .B ENOENT
 216 .I linkpath
 217 is a relative pathname and
 218 .IR newdirfd
 219 refers to a directory that has been deleted.
 220 .TP
 221 .B ENOTDIR
 222 .I linkpath
 223 is relative and
 224 .I newdirfd
 225 is a file descriptor referring to a file other than a directory.
 226 .SH VERSIONS
 227 .BR symlinkat ()
 228 was added to Linux in kernel 2.6.16;
 229 library support was added to glibc in version 2.4.
 230 .SH CONFORMING TO
 231 .BR symlink ():
 232 SVr4, 4.3BSD, POSIX.1-2001, POSIX.1-2008.
 233 .\" SVr4 documents additional error codes EDQUOT and ENOSYS.
 234 .\" See
 235 .\" .BR open (2)
 236 .\" re multiple files with the same name, and NFS.
 237
 238 .BR symlinkat ():
 239 POSIX.1-2008.
 240 .SH NOTES
 241 No checking of
 242 .I target
 243 is done.
 244
 245 Deleting the name referred to by a symbolic link will actually delete the
 246 file (unless it also has other hard links).
 247 If this behavior is not desired, use
 248 .BR link (2).
 249 .SS Glibc notes
 250 On older kernels where
 251 .BR symlinkat ()
 252 is unavailable, the glibc wrapper function falls back to the use of
 253 .BR symlink (2).
 254 When
 255 .I linkpath
 256 is a relative pathname,
 257 glibc constructs a pathname based on the symbolic link in
 258 .IR /proc/self/fd
 259 that corresponds to the
 260 .IR newdirfd
 261 argument.
 262 .SH SEE ALSO
 263 .BR ln (1),
 264 .BR lchown (2),
 265 .BR link (2),
 266 .BR lstat (2),
 267 .BR open (2),
 268 .BR readlink (2),
 269 .BR rename (2),
 270 .BR unlink (2),
 271 .BR path_resolution (7),
 272 .BR symlink (7)