CODEWITHSUNDEEP
arraysbashif-statement
Requist
Requist

Reputation: 165

Bash check array for existing directories

Why does an empty variable test true if I check for existing directory?

I have two array's with a couple of dirs to process, which I loop / check like this:

for n in {1..20}
do
   if test -d ${dir[$n]}
   then
       echo "Execute ${dir[$n]}"
   fi
   if test -d ${other[$n]}
   then
       echo "Execute ${other[$n]}"
   fi 
done

However, after execution of the existing dirs the script also tries to execute the none existing array elements. It does not matter if I check for dir, file or even nonempty file.
Why?

Of course I can do a separate check if an element exists before checking if the dir exist, but can I not do this in one check?

Upvotes: 0

Views: 797

Answers (1)

user3392484
user3392484

Reputation: 1919

Put your ${foo[$n]} in double quotes:

if test -d "${dir[$n]}"

Consider:

$ test -d '' || echo false
false
$ test -d || echo false
$

In general, always put variable dereferences into double quotes. If you don't and a variable is undefined then bad things happen, as you're seeing here.

Upvotes: 1

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