Bash script to create directories and files with a numbered prefix

I wrote a pretty simple bash script. It takes a directory with subdirectories with incremental prefixes in their names (01test, 02test, 03test), creates a new directory with the next highest prefix and creates a couple of files and fills them with some default text.

I'd like to do this in fewer lines of code and eliminate redundancies.

#!/bin/bash

LAST=`exec ls example_dir | sed 's/\([0-9]\+\).*/\1/g' | sort -n | tail -1`
PREFIX="${LAST:0:2}"
PREFIX=$((PREFIX + 1))
PREFIX="$PREFIX"_
ARGS=$@
TESTNAME="${ARGS// /_}"
DIRNAME="example_dir/$PREFIX$TESTNAME"

mkdir $DIRNAME
mkdir $DIRNAME/some_directory
mkdir $DIRNAME/expected

touch $DIRNAME/first.txt
touch $DIRNAME/second.txt
touch $DIRNAME/third.json

echo "{" >> $DIRNAME/test.json
echo -e "\t\"enabled\": true" >> $DIRNAME/test.json
echo "}" >> $DIRNAME/test.json

echo "{" >> $DIRNAME/some_directory/$PREFIX.json
echo -e "  \"entities\": [" >> $DIRNAME/some_directory/$PREFIX.json
echo "  ]" >> $DIRNAME/some_directory/$PREFIX.json
echo "}" >> $DIRNAME/some_directory/$PREFIX.json

-
tail must to read the whole file. Calling sort with a -r (aka --reverse option) you can use head instead.

-
touch takes multiple arguments. You may

touch $DIRNAME/first.txt $DIRNAME/second.txt $DIRNAME/third.json

and further use brace expansion:

touch $DIRNAME/{first.txt,second.txt,third.json}

-
I would consider here-documenting the json files instead of echoing them, along the lines of:

cat > $DIRNAME/test.json
{
     "enabled": true
}
EOF

StackExchange Code Review Q#119343, answer score: 3