7

Let me give an example (it's just an example taken from here):

$ ls -l /usr/bin/gnome-text-editor 
lrwxrwxrwx 1 root root 35 Mar 16  2015 /usr/bin/gnome-text-editor -> /etc/alternatives/gnome-text-editor
$ ls -l /etc/alternatives/gnome-text-editor
lrwxrwxrwx 1 root root 14 Mar 16  2015 /etc/alternatives/gnome-text-editor -> /usr/bin/gedit
$ ls -l /usr/bin/gedit
-rwxr-xr-x 1 root root 588064 Mar 27  2014 /usr/bin/gedit

Here you can see that I've to use ls -l three times for reaching to destination. (3rd time is for making sure that /usr/bin/gedit is not a link`)

Is there any way (by means of making script or another command etc.) that I can get expected output like:

$ <improved ls -l> /usr/bin/gnome-text-editor 
lrwxrwxrwx 1 root root 35 Mar 16  2015 /usr/bin/gnome-text-editor -> /etc/alternatives/gnome-text-editor
lrwxrwxrwx 1 root root 14 Mar 16  2015 /etc/alternatives/gnome-text-editor -> /usr/bin/gedit

Another good output may be:

$ <some-command> /usr/bin/gnome-text-editor
/usr/bin/gnome-text-editor > /etc/alternatives/gnome-text-editor > /usr/bin/gedit
1
  • Also be aware, that links can be circular: a -> b b -> a
    – gilhad
    Mar 18, 2016 at 16:00

3 Answers 3

13

In this case, that's a Debian "alternative", so to get more details, you could use:

$ update-alternatives --display gnome-text-editor
gnome-text-editor - auto mode
  link best version is /usr/bin/gedit
  link currently points to /usr/bin/gedit
  link gnome-text-editor is /usr/bin/gnome-text-editor
  slave gnome-text-editor.1.gz is /usr/share/man/man1/gnome-text-editor.1.gz
/usr/bin/gedit - priority 50
  slave gnome-text-editor.1.gz: /usr/share/man/man1/gedit.1.gz
/usr/bin/leafpad - priority 40
  slave gnome-text-editor.1.gz: /usr/share/man/man1/leafpad.1.gz

More generally, on Linux, you can use the namei command to know about all the symlinks involved in the resolution of a path (also mount points with -x):

$ namei -lx /usr/bin/gnome-text-editor
f: /usr/bin/gnome-text-editor
Drwxr-xr-x root root /
drwxr-xr-x root root usr
drwxr-xr-x root root bin
lrwxrwxrwx root root gnome-text-editor -> /etc/alternatives/gnome-text-editor
Drwxr-xr-x root root   /
drwxr-xr-x root root   etc
drwxr-xr-x root root   alternatives
lrwxrwxrwx root root   gnome-text-editor -> /usr/bin/gedit
Drwxr-xr-x root root     /
drwxr-xr-x root root     usr
drwxr-xr-x root root     bin
-rwxr-xr-x root root     gedit

For a more direct answer to your question, I'd do something like:

#! /bin/zsh -
zmodload zsh/stat || exit
ret=0
for file do
  n=0
  while
    ls -ld -- "$file" || ! ret=1 && [ -L "$file" ]
  do
    if ((++n > 40)) && [ ! -e "$file" ]; then
      echo >&2 too many symlinks
      ret=1
      break
    fi
    zstat -A target +link -- "$file" || ! ret=1 || break
    case $target in
      (/*) file=$target;;
      (*)  file=$file:h/$target
    esac
  done
done
exit "$ret"

That may not give you all the information you need to understand what's going on. Compare for instance:

$ ./resolve-symlink b/b/b/b/x/b
lrwxrwxrwx 1 stephane stephane 1 Mar 18 15:37 b/b/b/b/x/b -> a
lrwxrwxrwx 1 stephane stephane 4 Mar 18 15:37 b/b/b/b/x/a -> ../a
lrwxrwxrwx 1 stephane stephane 26 Mar 18 15:15 b/b/b/b/x/../a -> /usr/bin/gnome-text-editor
lrwxrwxrwx 1 root root 35 Nov  5  2013 /usr/bin/gnome-text-editor -> /etc/alternatives/gnome-text-editor
lrwxrwxrwx 1 root root 14 Mar 15 12:21 /etc/alternatives/gnome-text-editor -> /usr/bin/gedit
-rwxr-xr-x 1 root root 10344 Nov 12 17:18 /usr/bin/gedit

With:

$ namei -lx b/b/b/b/x/b
f: b/b/b/b/x/b
lrwxrwxrwx stephane stephane b -> .
drwxr-xr-x stephane stephane   .
lrwxrwxrwx stephane stephane b -> .
drwxr-xr-x stephane stephane   .
lrwxrwxrwx stephane stephane b -> .
drwxr-xr-x stephane stephane   .
lrwxrwxrwx stephane stephane b -> .
drwxr-xr-x stephane stephane   .
lrwxrwxrwx stephane stephane x -> 2
drwxr-xr-x stephane stephane   2
lrwxrwxrwx stephane stephane b -> a
lrwxrwxrwx stephane stephane   a -> ../a
drwxr-xr-x stephane stephane     ..
lrwxrwxrwx stephane stephane     a -> /usr/bin/gnome-text-editor
Drwxr-xr-x root     root           /
drwxr-xr-x root     root           usr
drwxr-xr-x root     root           bin
lrwxrwxrwx root     root           gnome-text-editor -> /etc/alternatives/gnome-text-editor
Drwxr-xr-x root     root             /
drwxr-xr-x root     root             etc
drwxr-xr-x root     root             alternatives
lrwxrwxrwx root     root             gnome-text-editor -> /usr/bin/gedit
Drwxr-xr-x root     root               /
drwxr-xr-x root     root               usr
drwxr-xr-x root     root               bin
-rwxr-xr-x root     root               gedit
0
10

readlink is the command you are looking for.

$ readlink -e /usr/bin/gnome-text-editor
/usr/bin/gedit

Various flags (-f, -e, -m) are available according to how you'd like to behave in case of broken links - see man readlink for details.

1
  • Thanks; but it doesn't give the information about intermediate file(s) (like /etc/alternatives/gnome-text-editor) which may be useful
    – Pandya
    Mar 18, 2016 at 16:05
2

You can use the following script:

$ cat myll
#!/bin/bash
name="$1"
while [[ -L "$name" ]]; do
ls -l "$name"; 
name=`readlink "$name"`;
done

Example output:

$ myll /usr/bin/gnome-text-editor
lrwxrwxrwx 1 root root 35 Mar 16  2015 /usr/bin/gnome-text-editor -> /etc/alternatives/gnome-text-editor
lrwxrwxrwx 1 root root 14 Mar 16  2015 /etc/alternatives/gnome-text-editor -> /usr/bin/gedit

Here [[ -L "$name" ]] checks whether file is link or not and readlink "$name" reads link and save it to variable name for next loop. And hence while [[ -L "$name" ]] loops until original target/file reached.


For second work-around, you can use:

#!/bin/bash
name="$1"
while [[ -L "$name" ]]; do
echo -n "$name > ";
name=`readlink "$name"`;
done
echo "$name"

Example output:

$ myls /usr/bin/gnome-text-editor
/usr/bin/gnome-text-editor > /etc/alternatives/gnome-text-editor > /usr/bin/gedit
1
  • 2
    That won't work properly for relative symlinks (as relative symlinks are relative to the symlink's host directory, not to your current working directory). Mar 18, 2016 at 14:57

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