warning insecure world writable dir ruby mode 040777，gem insstal sass error failed to build gem nati

//1.删除原gem源
gem sources --remove https://rubygems.org/

//2.添加国内镜像
gem source -a https://gems.ruby-china.com

//3.打印是否替换成功
gem sources -l

//4.更换成功后打印如下
*** CURRENT SOURCES ***
 https://gems.ruby-china.com

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

    current directory: /var/lib/gems/2.5.0/gems/ffi-1.11.1/ext/ffi_c
/usr/bin/ruby2.5 -r ./siteconf20190522-24821-9c6o4.rb extconf.rb
mkmf.rb can't find header files for ruby at /usr/lib/ruby/include/ruby.h

extconf failed, exit code 1

Gem files will remain installed in /var/lib/gems/2.5.0/gems/ffi-1.11.1 for inspection.
Results logged to /var/lib/gems/2.5.0/extensions/x86_64-linux/2.5.0/ffi-1.11.1/gem_make.out

sh -c "$(curl -fsSL https://raw.githubusercontent.com/Linuxbrew/install/master/install.sh)"

test -d ~/.linuxbrew && eval $(~/.linuxbrew/bin/brew shellenv)
test -d /home/linuxbrew/.linuxbrew && eval $(/home/linuxbrew/.linuxbrew/bin/brew shellenv)
test -r ~/.bash_profile && echo "eval \$($(brew --prefix)/bin/brew shellenv)" >>~/.bash_profile
echo "eval \$($(brew --prefix)/bin/brew shellenv)" >>~/.profile

brew install hello

sudo apt-get install ruby-full

brew install ruby

landv@Desktop201712556489:~/node$ sass -v
bash: sass: 未找到命令
landv@Desktop201712556489:~/node$ 

ERROR:  While executing gem ... (Errno::EACCES)
Permission denied @ rb_sysopen - /Library/Ruby/Gems/2.3.0/gems/fuzzy_match-2.1.0/.gitignore

sudo gem install cocoapods-core

sudo apt-get install ruby-full