47

How can I take any given path in bash and convert it to it's canonical form, dereferencing any symbolic links that may be contained within the path?

For example:

~$ mkdir /tmp/symtest
~$ cd /tmp/symtest/
/tmp/symtest$ mkdir -p foo/bar cat/dog
/tmp/symtest$ cd foo/bar/
/tmp/symtest/foo/bar$ ln -s ../../cat cat
/tmp/symtest/foo/bat$ cd ../../
/tmp/symtest$ tree
.
|-- cat
|   `-- dog
`-- foo
    `-- bar
       `-- cat -> ../../cat

6 directories, 0 files

How can I get the full canonical path of /tmp/symtest/foo/bar/cat (i.e: /tmp/symtest/cat)?

David Dean
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2 Answers2

70

Thanks to Andy Skelton, it appears the answer is readlink -f:

$:/tmp/symtest$ readlink -f /tmp/symtest/foo/bar/cat
/tmp/symtest/cat
David Dean
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    In macOS bash, the -f option is not present for readlink, it is used for the format of the related stat command, that shares a man page with readlink. The only valid readlink option for macOS bash appears to be: -n Do not force a newline to appear at the end of each piece of output. – Lucifer Morningstar Oct 03 '19 at 17:20
-7

Here's a function that will resolve symbolic links
It's original purpose is to resolve the full path to the calling script pointed to by a /usr/bin symlink

# resolve symbolic links
function resolve_link() {
  local LINK_FILE=${1:-${BASH_SOURCE[0]}}
  local FILE_TYPE=`file $LINK_FILE | awk '{print $2}'`
  local LINK_TO=$LINK_FILE
  while [ $FILE_TYPE = "symbolic" ]; do
    LINK_TO=`readlink $LINK_FILE`
    FILE_TYPE=`file $LINK_TO | awk '{print $2}'`
  done
  echo $LINK_TO
}

BASH_SOURCE_RESOLVED=$(resolve_link)
echo $BASH_SOURCE_RESOLVED

It doesn't use recursion but then again I've never used recursion in bash

usbdongle
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    Um, what? This is needlessly complicated, replicating the standard `readlink -f` functionality without need. Not to mention that the correct answer was posted 3 years ago... – cha0site Mar 24 '12 at 14:59
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    P.S. See this SO answer: http://stackoverflow.com/questions/1055671/how-can-i-get-the-behavior-of-gnus-readlink-f-on-a-mac for a saner solution for systems that don't have `readlink -f`, such as Mac OS X. – cha0site Mar 24 '12 at 15:02