CONTAINER="name"
DB="Db name"
TABLE="Table Name"
FILE="file.csv"

sudo docker exec -u postgres ${CONTAINER} psql -d ${DB} -c "COPY ${TABLE} TO STDOUT WITH CSV HEADER " > ${FILE}

# Copy csv to table
# sudo psql -h localhost -U root -d my_db -p 5432  -c "\COPY source_table TO  '/home/user/source_table.csv' DELIMITER ',' CSV HEADER;"