Install the latest version of a composer programmatically

If you need to install the latest version of a composer you can use next bash snippet:

EXPECTED_SIGNATURE=$(wget -q -O - https://composer.github.io/installer.sig) && \
php -r "copy('https://getcomposer.org/installer', 'composer-setup.php');" && \
php -r "if (hash_file('SHA384', 'composer-setup.php') === '${EXPECTED_SIGNATURE}') { echo 'Installer verified'; } else { echo 'Installer corrupt'; unlink('composer-setup.php'); } echo PHP_EOL;" && \
php composer-setup.php && \
php -r "unlink('composer-setup.php');" && \
mv composer.phar /usr/local/bin/composer

Using EXPECTED_SIGNATURE variable with the latest available signature value you don't have to hardcode a specific one for comparison on 3rd line.