Modify the environment instead of prepending a path.

Gemfile

@@ -1,4 +1,5 @@
 source 'http://rubygems.org'
 group :development do
+  gem 'rake'
   gemspec :name => "cocaine"
 end

Gemfile.lock

@@ -11,12 +11,12 @@ GEM
     diff-lcs (1.1.2)
     mocha (0.9.8)
       rake
-    rake (0.8.7)
+    rake (0.9.1)
     rspec (2.6.0)
       rspec-core (~> 2.6.0)
       rspec-expectations (~> 2.6.0)
       rspec-mocks (~> 2.6.0)
-    rspec-core (2.6.0)
+    rspec-core (2.6.3)
     rspec-expectations (2.6.0)
       diff-lcs (~> 1.1.2)
     rspec-mocks (2.6.0)
@@ -28,4 +28,5 @@ DEPENDENCIES
   bourne
   cocaine!
   mocha
+  rake
   rspec

lib/cocaine/command_line.rb

@@ -15,15 +15,18 @@ def initialize(binary, params = "", options = {})
 
     def command
       cmd = []
-      cmd << full_path(@binary)
+      cmd << @binary
       cmd << interpolate(@params, @options)
       cmd << bit_bucket if @swallow_stderr
-      cmd.join(" ")
+      cmd.join(" ").strip
     end
 
     def run
+      output = ''
       begin
-        output = self.class.send(:'`', command)
+        with_modified_path do
+          output = self.class.send(:'`', command)
+        end
       rescue Errno::ENOENT
         raise Cocaine::CommandNotFoundError
       end
@@ -38,8 +41,15 @@ def run
 
     private
 
-    def full_path(binary)
-      [self.class.path, binary].compact.join("/")
+    def with_modified_path
+      begin
+        saved_path = ENV['PATH']
+        extra_path = [self.class.path].flatten
+        ENV['PATH'] = [ENV['PATH'], *extra_path].join(File::PATH_SEPARATOR)
+        yield
+      ensure
+        ENV['PATH'] = saved_path
+      end
     end
 
     def interpolate(pattern, vars)

spec/cocaine/command_line_spec.rb

@@ -11,10 +11,20 @@
     cmd.command.should == "convert a.jpg b.png"
   end
 
-  it "can set a default path and produce commands with that path" do
-    Cocaine::CommandLine.path = "/opt/bin"
-    cmd = Cocaine::CommandLine.new("convert", "a.jpg b.png", :swallow_stderr => false)
-    cmd.command.should == "/opt/bin/convert a.jpg b.png"
+  it "specifies the path where the command should be run" do
+    Cocaine::CommandLine.path = "/path/to/command/dir"
+    cmd = Cocaine::CommandLine.new("ruby", "-e 'puts ENV[%{PATH}]'")
+    cmd.command.should == "ruby -e 'puts ENV[%{PATH}]'"
+    output = cmd.run
+    output.should match(%r{/path/to/command/dir})
+  end
+
+  it "specifies more than one path where the command should be run" do
+    Cocaine::CommandLine.path = ["/path/to/command/dir", "/some/other/path"]
+    cmd = Cocaine::CommandLine.new("ruby", "-e 'puts ENV[%{PATH}]'")
+    output = cmd.run
+    output.should match(%r{/path/to/command/dir})
+    output.should match(%r{/some/other/path})
   end
 
   it "can interpolate quoted variables into the parameters" do

spec/spec_helper.rb

@@ -1,5 +1,5 @@
 require 'rspec'
-require 'spec/support/with_exitstatus'
+require './spec/support/with_exitstatus'
 require 'mocha'
 require 'bourne'
 require 'cocaine'