How to mkdir only if a dir does not already exist?

Question

I am writing a script to run under the korn shell on AIX. I'd like to use the mkdir command to create a directory. But the directory may already exist, in which case I don't want to do anything. So I want to either test to see that the directory doesn't exist, or suppress the "File exists" error that mkdir throws when it tries to create an existing directory.

Any thoughts on how best to do this?

Answer 1

Try mkdir -p:

mkdir -p foo

Note that this will also create any intermediate directories that don't exist; for instance,

mkdir -p foo/bar/baz

will create directories foo, foo/bar, and foo/bar/baz if they don't exist.

If you want an error if parent directories don't exist, but want to create the directory if it doesn't exist, you can test for the existence of the directory first:

[ -d foo ] || mkdir foo

Answer 2

Use the -p flag.

man mkdir
mkdir -p foo

Answer 3

This should work:

$ mkdir -p dir

or:

if [[ ! -e $dir ]]; then
    mkdir $dir
elif [[ ! -d $dir ]]; then
    echo "$dir already exists but is not a directory" 1>&2
fi

which will create the directory if it doesn't exist, but warn you if the name of the directory you're trying to create is already in use by something other than a directory.

Answer 4

Or if you want to check for existence first:

if [[ ! -e /path/to/newdir ]]; then
            mkdir /path/to/newdir
fi

-e is the exist test for korn shell.

You can also try googling a korn shell manual.

Answer 5

Just mkdir again... if it already exsits... so what?

Answer 6

The old tried and true

mkdir /tmp/qq >/dev/null 2>&1

will do what you want with none of the race conditions many of the other solutions have.

Sometimes the simplest (and ugliest) solutions are the best :-)