In Linux we have a command called test, you can check whether a file/directory exists or not and run commands based on the result. For example let's say we want to check if a folder exists and if it does not exist, create the folder.

For checking directory existence we use test -d and for file existence we use test -f, so for our example in order to check if the directory exists we use test -d and in case the folder does not exists we will create it:

directory_to_check="/data/mysql"
 test -d $directory_to_check || {
     echo "$directory_to_check does not exist, creating the folder..." && mkdir -p $directory_to_check || {
         echo "$directory_to_check directory could not be created!"
         exit 1
     }
 }

NOTE: you can read more about exit codes with hashtag #exit_code

#bash #linux #directory_existence #file_existence