gem executables will not run - ruby

Question

Running gem install from shell script giving error even though I ruby version2.3.0 installed on my machine.
I am trying to install a gem from sh file. sh file code is as below:
cat > /tmp/install_bandshell.sh <<EOF
#!/bin/sh -e
cd /tmp
git clone git://github.com/concerto/bandshell.git
cd bandshell
gem build bandshell.gemspec
gem install *.gem
cd /
rm -rf /tmp/bandshell
EOF
chmod +x /tmp/install_bandshell.sh
/tmp/install_bandshell.sh
But when I run this sh file get error WARNING: You don't have /root/.gem/ruby/1.9.1/bin in your PATH, gem executables will not run. ERROR: Error installing bandshell-1.7.2.gem: rack requires Ruby version >= 2.2.2.
Even I install 2.3.0 gem env output
RubyGems Environment:
- RUBYGEMS VERSION: 2.5.1
- RUBY VERSION: 2.3.0 (2015-12-25 patchlevel 0) [x86_64-linux]
- INSTALLATION DIRECTORY: /usr/local/lib/ruby/gems/2.3.0/gems/
- USER INSTALLATION DIRECTORY: /root/.gem/ruby/2.3.0
- RUBY EXECUTABLE: /usr/local/bin/ruby
- EXECUTABLE DIRECTORY: /usr/local/lib/ruby/gems/2.3.0/gems/bin
- SPEC CACHE DIRECTORY: /root/.gem/specs
- SYSTEM CONFIGURATION DIRECTORY: /usr/local/etc
- RUBYGEMS PLATFORMS:
- ruby
- x86_64-linux
- GEM PATHS:
- /usr/local/lib/ruby/gems/2.3.0/gems/
- /root/.gem/ruby/2.3.0
- /usr/local/lib/ruby/gems/2.3.0
- GEM CONFIGURATION:
- :update_sources => true
- :verbose => true
- :backtrace => false
- :bulk_threshold => 1000
- REMOTE SOURCES:
- https://rubygems.org/
- SHELL PATH:
- /usr/local/sbin
- /usr/local/bin
- /usr/sbin
- /usr/bin
- /sbin
- /bin
- /usr/local/lib/ruby/gems/2.3.0/gems
From terminal, if I install this gem it works but from shell script giving above error. Please help me with this. Platform is Debian Wheezy.

Answer 1

I'm answering your primary question only, regarding the message. (Frankly, I don't know what's going on with your sh file, so I'm not going to address whatever other problems it causes.)
The message is a warning to you that any executables that the gem installs are not in your path. If the gem does not install any executables, then you can safely ignore the message. If it does (or you are simply unsure), then modify the path accordingly. How you do that depends on what shell you happen to be using. Since you have tagged the question with 'linux', I will guess that you are using bash; if so, add to either your ~/.profile or to ~/.bash_profile an entry similar to:
PATH="$PATH:/root/.gem/ruby/1.9.1/bin"
Now, at this point, I have to wonder - are you using ruby-1.9? You know that ruby 1.9 is obsolete, right? Actually, considering that you seem to be using Ruby 2.3.0, that's not likely. What I would suggest is to (at least temporarily) adjust your PATH as above to avoid the warning. I suspect you will still have problems, but then you can ask a new question without the WARNING that you have cited.
One last point, ignore suggestions that you should change your shebang to be other than "#!/bin/sh"; that's very unlikely to help.

Answer 2

Answering the WARNING: You don't have /root/.gem/ruby/1.9.1/bin in your PATH, gem executables will not run. problem...
Try add this line on your ~/.bashrc or ~/.zshrc:
export PATH="/root/.gem/ruby/1.9.1/bin:$PATH"