v

gem install rmagick
Building native extensions.  This could take a while...
ERROR:  Error installing rmagick:
        ERROR: Failed to build gem native extension.

        /usr/local/bin/ruby18 extconf.rb
checking for Ruby version >= 1.8.5... yes
checking for cc... yes
checking for Magick-config... no
Can't install RMagick 2.13.1. Can't find Magick-config in /sbin:/bin:/usr/sbin:/usr/bin:/usr/games:/usr/local/sbin:/usr/local/bin:/root/bin

*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers.  Check the mkmf.log file for more
details.  You may need configuration options.

Provided configuration options:
        --with-opt-dir
        --without-opt-dir
        --with-opt-include
        --without-opt-include=${opt-dir}/include
        --with-opt-lib
        --without-opt-lib=${opt-dir}/lib
        --with-make-prog
        --without-make-prog
        --srcdir=.
        --curdir
        --ruby=/usr/local/bin/ruby18


Gem files will remain installed in /usr/local/lib/ruby/gems/1.8/gems/rmagick-2.13.1 for inspection.
Results logged to /usr/local/lib/ruby/gems/1.8/gems/rmagick-2.13.1/ext/RMagick/gem_make.out