Shell script to export prefixed environment variables to JSON file

genenv.sh

#!/bin/bash
ENV_FILE="env.json"
ENV_PREFIX="REACT_APP_"

shopt -s lastpipe

FOUND=0

echo '{' > $ENV_FILE

env | while IFS= read -r line; do
  value=${line#*=}
  name=${line%%=*}

  if [[ "$name" == "$ENV_PREFIX"* ]]
  then
    if [[ $FOUND == 1 ]]
    then
        echo "$(cat $ENV_FILE)," > $ENV_FILE
    fi

    echo "        \"$name\": \"$value\"" >> $ENV_FILE
    FOUND=1
  fi
done

echo '}' >> $ENV_FILE