How do I send RUN's output to ENV in Dockerfile?

General
3

Thank You!

My final solution was to put the node.js archive download under the same command:

RUN NODE_VERSION=$( \
        curl -sL https://nodejs.org/dist/latest/ | \
        tac | \
        tac | \
        grep -oPa -m 1 '(?<=node-v)(.*?)(?=-linux-x64\.tar\.xz)' | \
        head -1 \
    ) \
    && echo $NODE_VERSION \
    && curl -SLO "https://nodejs.org/dist/latest/node-v$NODE_VERSION-linux-x64.tar.xz" -o "node-v$NODE_VERSION-linux-x64.tar.xz" \
    && curl -SLO "https://nodejs.org/dist/latest/SHASUMS256.txt.asc" \
    && gpg --batch --decrypt --output SHASUMS256.txt SHASUMS256.txt.asc \
    && grep " node-v$NODE_VERSION-linux-x64.tar.xz\$" SHASUMS256.txt | sha256sum -c - \
    && tar -xJf "node-v$NODE_VERSION-linux-x64.tar.xz" -C /usr/local --strip-components=1 \
    && rm "node-v$NODE_VERSION-linux-x64.tar.xz" SHASUMS256.txt.asc SHASUMS256.txt