How to check if a symlink exists

Question

I'm trying to check if a symlink exists in bash. Here's what I've tried.

mda=/usr/mda
if [ ! -L $mda ]; then
  echo "=> File doesn't exist"
fi


mda='/usr/mda'
if [ ! -L $mda ]; then
  echo "=> File doesn't exist"
fi

However, that doesn't work. If '!' is left out, it never triggers. And if '!' is there, it triggers every time.

Reahard

for what its worth, if you use [[ ! -D $mda ]] works just fine.. – Wang

Answer 1

-L returns true if the "file" exists and is a symbolic link (the linked file may or may not exist). You want -f (returns true if file exists and is a regular file) or maybe just -e (returns true if file exists regardless of type).

According to the GNU manpage, -h is identical to -L, but according to the BSD manpage, it should not be used:

-h file True if file exists and is a symbolic link. This operator is retained for compatibility with previous versions of this program. Do not rely on its existence; use -L instead.

Arsyvarsy

I'm looking to see if a symlink DOESN'T exist. !-h or !-L should work for symlinks, !-e should work otherwise. – Reahard

To help anyone who finds this via Google as I did, the full syntax using ! is if ! [ -L $mda ]; then .... fi i.e. put the exclamation mark outside the square brackets. – Aldas

Just wanted to add a little something to the tip given by @Sam; when doing these sorts of operations make sure to put your file name in quotes, to prevent issues with whitespaces. e.g. if [ ! -L "$mda" ]; then ... fi (note: if [ ! ... ] and if ! [ ... ] are identical :) – Nihility

do you really see a difference between -L and -h ? in my bash ( version 4.2.53(1)-release (x86_64-redhat-linux-gnu ) man bash is identical for both -L and -h and they behave the same, ie they check that file actualy is a link and don't care whether the linked to file exists or not. – Grata

Yes, -L and -h are the same. man test also confirms this. – Counterinsurgency

Anybody has an idea how to check whether the target file exists? – Art

@Counterinsurgency - any idea why they might be synonymous in the first place? The best reason my googling came up with is "because it's bash" – Cassidy

@Cassidy No idea… I thought I remembered some commands where -h was to do with symlinks, but I can't seem to find them now. cp -H is similar I guess, although mostly -h is to show the help. You should ask it as a question (perhaps in Unix/Linux)! – Counterinsurgency

@Cassidy man test on BSD's test provided some insight about -h: This operator is retained for compatibility with previous versions of this program. Do not rely on its existence; use -L instead. As for why they changed to -L over -h, I have no idea – Christian

@TomášZato -e $(readlink -f $symlink) would check if the linked file exists, but has the caveat that is also return true if $symlink exists but is not actually a symlink. – Christian

it seems if a link is broken, -e doesn't work but only -L can tell if the link exist (though the linked file doesn't exist). Is there anyway to test if a file/or even broken link exist ? – Adjudication

-f also return true if the file is a symbolic link and target is exist. – Coquet

@Adjudication Just ran into a super annoying bug because of this. This detail should probably be added to the answer to help others in the future. – Rosenberg

Answer 2

You can check the existence of a symlink and that it is not broken with:

[ -L ${my_link} ] && [ -e ${my_link} ]

So, the complete solution is:

if [ -L ${my_link} ] ; then
   if [ -e ${my_link} ] ; then
      echo "Good link"
   else
      echo "Broken link"
   fi
elif [ -e ${my_link} ] ; then
   echo "Not a link"
else
   echo "Missing"
fi

-L tests whether there is a symlink, broken or not. By combining with -e you can test whether the link is valid (links to a directory or file), not just whether it exists.

Sepulveda

-L test if there is a symlink, broken or not. By combining with -e it is possible to test if the link is also valid (linking to a directory or file). Up-voting this solutions, since I find it important to capture this aspect. – Counterblast

Thanks ! I'm struggling with the logic behind if, this post really helped me ! +1 – Tensile

bash friendly: if [[ -L "${my_link}" ]]; then ... – Sweatt

Answer 3

-L is the test for file exists and is also a symbolic link

If you do not want to test for the file being a symbolic link, but just test to see if it exists regardless of type (file, directory, socket etc) then use -e

So if file is really file and not just a symbolic link you can do all these tests and get an exit status whose value indicates the error condition.

if [ ! \( -e "${file}" \) ]
then
     echo "%ERROR: file ${file} does not exist!" >&2
     exit 1
elif [ ! \( -f "${file}" \) ]
then
     echo "%ERROR: ${file} is not a file!" >&2
     exit 2
elif [ ! \( -r "${file}" \) ]
then
     echo "%ERROR: file ${file} is not readable!" >&2
     exit 3
elif [ ! \( -s "${file}" \) ]
then
     echo "%ERROR: file ${file} is empty!" >&2
     exit 4
fi

Oxygen

-e "${file}" fails if the symlink exists but its target does not exist. – Salzburg

Same result as Flimm. I'm on OS X. For me, -L and -h work for symlinks, but not -e or -f. – Cila

@Flimm, so if I just want to test if a filename is taken (whether it's a file or symlink without target existing) what's the best way to do it? apparently -e doesn't work – Adjudication

@Adjudication maybe [ -L $file_or_link ] || [ -e $file_or_link ]? – Esme

Answer 4

Maybe this is what you are looking for. To check if a file exist and is not a link.

Try this command:

file="/usr/mda" 
[ -f $file ] && [ ! -L $file ] && echo "$file exists and is not a symlink"

Traffic

Answer 5

How about using readlink?

# if symlink, readlink returns not empty string (the symlink target)
# if string is not empty, test exits w/ 0 (normal)
#
# if non symlink, readlink returns empty string
# if string is empty, test exits w/ 1 (error)
simlink? () {
  test "$(readlink "${1}")";
}

FILE=/usr/mda

if simlink? "${FILE}"; then
  echo $FILE is a symlink
else
  echo $FILE is not a symlink
fi

Dafna

Answer 6

Is the file really a symbolic link? If not, the usual test for existence is -r or -e.

See man test.

Wendy

Answer 7

1. first you can do with this style:

   mda="/usr/mda"
   if [ ! -L "${mda}" ]; then
     echo "=> File doesn't exist"
   fi
   

2. if you want to do it in more advanced style you can write it like below:

   #!/bin/bash
   mda="$1"
   if [ -e "$1" ]; then
       if [ ! -L "$1" ]
       then
           echo "you entry is not symlink"
       else
           echo "your entry is symlink"
       fi
   else
     echo "=> File doesn't exist"
   fi
   

the result of above is like:

root@linux:~# ./sym.sh /etc/passwd
you entry is not symlink
root@linux:~# ./sym.sh /usr/mda 
your entry is symlink
root@linux:~# ./sym.sh 
=> File doesn't exist

Luminescent

The first invocation is wrong if the file exists but is not a link, or is a dangling link. The second is wrong if the path is a dangling symlink. – Tidewaiter

Answer 8

If you are testing for file existence you want -e not -L. -L tests for a symlink.

Patchy

I'm looking to see if a symlink DOESN'T exist. !-h or !-L should work for symlinks, !-e should work otherwise. – Reahard

What you want is not clear. The file exists and is not a symlink? Then test both -e and !-h . – Patchy