fix code block

# hadoop-docker

```

docker compose up -d

docker exec -it --user hadoop namenode bash

cd /home/hadoop

hdfs dfs -mkdir /user

hdfs dfs -mkdir /user/hadoop

hdfs dfs -mkdir input

hadoop jar $STRJAR -mapper mapper.py -reducer reducer.py -input '/user/hadoop/input/*.txt' -output '/user/hadoop/output'

hdfs dfs -cat output/*

```

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