symlink

       Symbolic  links  are  files  that  act  as pointers to other files.  To
       understand their behavior, you must first  understand  how  hard  links
       work.

       A  hard  link  to  a  file  is indistinguishable from the original file
       because it is a reference to the object underlying the  original  file-
       name.   (To be precise: each of the hard links to a file is a reference
       to the same inode number, where an inode number is an  index  into  the
       inode  table,  which contains metadata about all files on a filesystem.
       See stat(2).)  Changes to a file are independent of the  name  used  to
       reference  the  file.  Hard links may not refer to directories (to pre-
       vent the possibility of loops within the filesystem tree,  which  would
       confuse many programs) and may not refer to files on different filesys-
       tems (because inode numbers are not unique across filesystems).

       A symbolic link is a special type of file whose contents are  a  string
       that  is  the  pathname  of  another  file,  the file to which the link
       refers.  (The contents of a symbolic  link  can  be  read  using  read-
       link(2).)   In  other  words,  a  symbolic link is a pointer to another
       name, and not to an underlying object.  For this reason, symbolic links
       may refer to directories and may cross filesystem boundaries.

       There  is  no  requirement  that the pathname referred to by a symbolic
       link should exist.  A symbolic link that refers to a pathname that does
       not exist is said to be a dangling link.

       Because  a  symbolic  link  and  its  referenced  object coexist in the
       filesystem name space, confusion can arise  in  distinguishing  between
       the link itself and the referenced object.  On historical systems, com-
       mands and system calls adopted their own link-following conventions  in
       a  somewhat ad-hoc fashion.  Rules for a more uniform approach, as they
       are implemented on Linux and other systems, are outlined here.   It  is
       important  that site-local applications also conform to these rules, so
       that the user interface can be as consistent as possible.

   Symbolic link ownership, permissions, and timestamps
       The owner and group of an existing symbolic link can be  changed  using
       lchown(2).  The only time that the ownership of a symbolic link matters
       is when the link is being removed or renamed in a  directory  that  has
       the sticky bit set (see stat(2)).

       The last access and last modification timestamps of a symbolic link can
       be changed using utimensat(2) or lutimes(3).

       On Linux, the permissions of a symbolic link are not used in any opera-
       tions;  the  permissions  are always 0777 (read, write, and execute for
       all user categories), and can't be changed.

   Obtaining a file descriptor that refers to a symbolic link
       Using the combination of the O_PATH and  O_NOFOLLOW  flags  to  open(2)
       yields  a  file  descriptor that can be passed as the dirfd argument in
       system calls such as fstatat(2), fchownat(2),  fchmodat(2),  linkat(2),
       and  readlinkat(2),  in  order  to  operate on the symbolic link itself
       (rather than the file to which it refers).
       by operating on the object referred to by  the  link.   In  the  latter
       case,  an  application or system call is said to follow the link.  Sym-
       bolic links may refer to other symbolic links, in which case the  links
       are  dereferenced until an object that is not a symbolic link is found,
       a symbolic link that refers to a file which does not exist is found, or
       a  loop is detected.  (Loop detection is done by placing an upper limit
       on the number of links that may be followed, and an  error  results  if
       this limit is exceeded.)

       There  are three separate areas that need to be discussed.  They are as
       follows:

       1. Symbolic links used as filename arguments for system calls.

       2. Symbolic links specified as command-line arguments to utilities that
          are not traversing a file tree.

       3. Symbolic  links  encountered by utilities that are traversing a file
          tree (either specified on the command line or encountered as part of
          the file hierarchy walk).

   System calls
       The  first area is symbolic links used as filename arguments for system
       calls.

       Except as noted below, all system calls  follow  symbolic  links.   For
       example,  if  there  were a symbolic link slink which pointed to a file
       named afile, the system call open("slink"  ...)  would  return  a  file
       descriptor referring to the file afile.

       Various  system  calls do not follow links, and operate on the symbolic
       link itself.  They are: lchown(2),  lgetxattr(2),  llistxattr(2),  lre-
       movexattr(2), lsetxattr(2), lstat(2), readlink(2), rename(2), rmdir(2),
       and unlink(2).

       Certain other system calls optionally follow symbolic links.  They are:
       faccessat(2), fchownat(2), fstatat(2), linkat(2), name_to_handle_at(2),
       open(2), openat(2), open_by_handle_at(2), and utimensat(2);  see  their
       manual pages for details.  Because remove(3) is an alias for unlink(2),
       that library function  also  does  not  follow  symbolic  links.   When
       rmdir(2)  is  applied to a symbolic link, it fails with the error ENOT-
       DIR.

       link(2)  warrants  special  discussion.   POSIX.1-2001  specifies  that
       link(2)  should dereference oldpath if it is a symbolic link.  However,
       Linux does not do this.  (By default, Solaris  is  the  same,  but  the
       POSIX.1-2001  specified behavior can be obtained with suitable compiler
       options.)  POSIX.1-2008  changed  the  specification  to  allow  either
       behavior in an implementation.

   Commands not traversing a file tree
       The  second  area is symbolic links, specified as command-line filename
       arguments, to commands which are not traversing a file tree.

       link instead of following the symbolic link--for example, it is desired
       that  chown  slink  change  the  ownership  of  the file that slink is,
       whether it is a symbolic link or not--the -h option should be used.  In
       the  above  example, chown root slink would change the ownership of the
       file referred to by slink, while chown -h root slink would  change  the
       ownership of slink itself.

       There are some exceptions to this rule:

       * The  mv(1)  and  rm(1) commands do not follow symbolic links named as
         arguments, but  respectively  attempt  to  rename  and  delete  them.
         (Note,  if  the  symbolic link references a file via a relative path,
         moving it to another directory may very well cause it to  stop  work-
         ing, since the path may no longer be correct.)

       * The ls(1) command is also an exception to this rule.  For compatibil-
         ity with historic systems (when ls(1) is not doing a tree  walk--that
         is,  -R  option is not specified), the ls(1) command follows symbolic
         links named as arguments if the -H or -L option is specified,  or  if
         the  -F,  -d, or -l options are not specified.  (The ls(1) command is
         the only command where the -H and -L options affect its behavior even
         though it is not doing a walk of a file tree.)

       * The  file(1)  command is also an exception to this rule.  The file(1)
         command does not follow symbolic links named as argument by  default.
         The  file(1)  command does follow symbolic links named as argument if
         the -L option is specified.

   Commands traversing a file tree
       The following commands either optionally or always traverse file trees:
       chgrp(1),  chmod(1),  chown(1),  cp(1),  du(1), find(1), ls(1), pax(1),
       rm(1), and tar(1).

       It is important to realize that the following rules  apply  equally  to
       symbolic  links encountered during the file tree traversal and symbolic
       links listed as command-line arguments.

       The first rule applies to symbolic links  that  reference  files  other
       than  directories.   Operations  that  apply to symbolic links are per-
       formed on the links themselves, but otherwise the links are ignored.

       The command rm -r slink directory will remove slink,  as  well  as  any
       symbolic  links encountered in the tree traversal of directory, because
       symbolic links may be removed.  In no case will rm(1) affect  the  file
       referred to by slink.

       The  second  rule  applies to symbolic links that refer to directories.
       Symbolic links that refer to directories are never followed by default.
       This  is often referred to as a "physical" walk, as opposed to a "logi-
       cal" walk (where symbolic links that  refer  to  directories  are  fol-
       lowed).

       Certain  conventions are (should be) followed as consistently as possi-
       ble by commands that perform file tree walks:
         the  purposes  of  both the action to be performed and the tree walk,
         and it is as if the user had specified the name of the file to  which
         the symbolic link pointed.

       * A  command can be made to follow any symbolic links named on the com-
         mand line, as well as any symbolic links encountered during the  tra-
         versal,  regardless of the type of file they reference, by specifying
         the -L (for "logical") flag.  This  flag  is  intended  to  make  the
         entire  name space look like the logical name space.  (Note, for com-
         mands that do not always do file tree traversals, the -L flag will be
         ignored if the -R flag is not also specified.)

         For  example,  the command chown -LR user slink will change the owner
         of the file referred to by slink.  If slink refers  to  a  directory,
         chown  will  traverse the file hierarchy rooted in the directory that
         it references.  In addition, if any symbolic links are encountered in
         any  file tree that chown traverses, they will be treated in the same
         fashion as slink.

       * A command can be made to provide the default behavior  by  specifying
         the  -P  (for  "physical")  flag.   This flag is intended to make the
         entire name space look like the physical name space.

       For commands that do not by default do file tree  traversals,  the  -H,
       -L,  and -P flags are ignored if the -R flag is not also specified.  In
       addition, you may specify the -H, -L, and -P options  more  than  once;
       the  last  one  specified  determines  the command's behavior.  This is
       intended to permit you to alias commands  to  behave  one  way  or  the
       other, and then override that behavior on the command line.

       The ls(1) and rm(1) commands have exceptions to these rules:

       * The  rm(1) command operates on the symbolic link, and not the file it
         references, and therefore never follows a symbolic link.   The  rm(1)
         command does not support the -H, -L, or -P options.

       * To  maintain  compatibility  with historic systems, the ls(1) command
         acts a little differently.  If you do not specify the -F,  -d  or  -l
         options,  ls(1)  will  follow symbolic links specified on the command
         line.  If the -L flag is specified, ls(1) follows all symbolic links,
         regardless  of  their  type, whether specified on the command line or
         encountered in the tree walk.

SEE ALSO
       chgrp(1), chmod(1), find(1), ln(1),  ls(1),  mv(1),  rm(1),  lchown(2),
       link(2),  lstat(2), readlink(2), rename(2), symlink(2), unlink(2), uti-
       mensat(2), lutimes(3), path_resolution(7)

COLOPHON
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