53

For use in a shell-script, I'm looking for a commandline-way to get the destination of a symbolic link. The closest I've come so far is stat -N src, which outputs src -> dst. Of course I could parse the output and get dst, but I wonder if there is some direct way of getting the destination.

65

Another option would be to use the specifically designed command readlink if available.

E.g.

$ readlink -f `command -v php`
/usr/bin/php7.1
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  • 22
    Use readlink -f if you want to know the last symlink target and not only the next one. – scai Sep 10 '12 at 14:25
  • 11
    Note that -f is a non-portable extension to GNU readlink. – bahamat Sep 10 '12 at 21:38
  • 2
    When would readlink not be available? Thanks. – tommy.carstensen Jul 29 '15 at 12:55
  • 2
    @tommy.carstensen readlink(1) was added to GNU coreutils in 2003, so these days you can likely depend on it on practically all systems using coreutils. (Cf. git.savannah.gnu.org/cgit/coreutils.git/commit/src/…) – Josip Rodin Oct 5 '15 at 12:55
  • 1
    readlink can give trouble in scripts, it return the destination of the link, relative to the link. readlink -f only gives the final destination. If you where looking to copy the symlink and its destination in the script, the symlink will break if it was pointing to another symlink. The intermediate will be missing. – Tim May 24 '18 at 12:28
18

On Mac OS X and FreeBSD/NetBSD/etc. it's:

stat -f %Y <filename>

More generically I guess the solution is (stat --printf=%N uses weird quotes):

ls -l b | sed -e 's/.* -> //'

Example:

# ln -s a b
# stat -f %Y b
a

Another method is:

# find b -maxdepth 0 -printf %l
a#

The last line is mangled because it has no newline, but that is fine if you need the result in a variable, like so

# f=$(find b -maxdepth 0 -printf %l)
# echo $f
a

The -maxdepth is needed to prevent find from descending into directories if b happens to be a directory.

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  • I totally skimmed over, stat --printf='%N\n' is exactly what I want, weird quotes don't bother me, their the same quotes rm and ln --interactive use – ThorSummoner Sep 30 '15 at 17:56
  • This apparently isn't portable because on Linux, the GNU coreutils' stat(1) has different parameters and prints out link -> dest in the output. The find(1) solution should be checked if it's with GNU findutils or otherwise... – Josip Rodin Oct 5 '15 at 11:06
  • Please don't forget to quote your variable expansions, echo $f certainly does not produce what you expect when the symlink points to /* (yes it's possible) – Camusensei Mar 17 '17 at 10:19
3

This can be done using GNU find: find src -prune -printf "%l\n".

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2

Portable pure Bash realpath

bash_realpath() {
  # print the resolved path
  # @params
  # 1: the path to resolve
  # @return
  # &1: the resolved link path

  local path="${1}"
  while [[ -L ${path} && "$(ls -l "${path}")" =~ -\>\ (.*) ]]
  do
    path="${BASH_REMATCH[1]}"
  done
  echo "${path}"
}
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1

Portably: no luck except using heuristics to parse ls -l output, or use perl -le 'print readlink("some-file")'

some systems have a readlink command, some with a -f option to obtain the absolute path.

There are various implementations of a stat command as a wrapper for the stat/lstat system calls. The GNU one is not useful in that regard, but zsh's builtin one is more so:

zmodload zsh/stat
stat +link the-link

Still with zsh, you can get the absolute path of a file (removes every symlink component) with the :A modifier (applies to variable expansion, history expansion and globbing:

~$ gstat -c %N b
`b' -> `a'
~$ var=b
~$ echo $var:A
/home/me/a
~$ echo b(:A)
/home/me/a
~$ echo ?(@:A)
/home/me/a
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1

realpath command of coreutils package,

as linked in readlink command's manual page.


for example:

realpath /bin/python

outputs

/usr/bin/python2.7

on my machine.

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1

On a system where I have no readlink or stat commands but I do have Python 2.x, I'm using a short script:

#!/usr/bin/env python

import os, sys

if __name__ == "__main__":
    src = sys.argv[1]
    target = os.readlink(src)
    if not os.path.isabs(target):
            target = os.path.abspath(os.path.join(os.path.dirname(src), target))
    print target

Note that unlike readlink -f this may only follow one level of symlink.

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0

Added a pure sh version, hoping it to be more portable if bash is not installed :

$ cat ./realpath.sh
#!/usr/bin/env sh

bash_realpath() {
  # print the resolved path
  # @params
  # 1: the path to resolve
  # @return
  # &1: the resolved link path

  for path;do
    while [ -L "${path}" ]
    do
      path="$(\ls -l "${path}" | awk '{print $NF}')"
    done
    which "${path}"
  done
}

bash_realpath "$@"

Use case :

$ ./realpath.sh $(which gcc python)
/usr/bin/x86_64-linux-gnu-gcc-6
/usr/bin/python2.7
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