allow passign env to cheetah (gh#17)

README.md

@@ -39,6 +39,7 @@ Features
   * 100% secure (shell expansion is impossible by design)
   * Raises exceptions on errors (no more manual status code checks)
   * allow specification of valid exit codes
+  * allow temporary overwrite of env variables
   * Optional logging for easy debugging
 
 Non-features
@@ -151,6 +152,14 @@ status, input and both outputs to it:
 Cheetah.run("ls -l", logger: logger)
 ```
 
+### Overwritting env
+
+If command need to have own specified ENV set, then passing :env option does it.
+
+```ruby
+  Cheetah.run("env", env: { "LC_ALL" => "C" })
+```
+
 ### Expecting Non-zero Exit Status
 
 If command is expected to return valid a non-zero exit status like `grep` command

lib/cheetah.rb

@@ -304,6 +304,9 @@ class << self
     #   @option options [Fixnum, .include?, nil] :allowed_exitstatus (nil)
     #     Allows to specify allowed exit codes that do not cause exception. It
     #     adds as last element of result exitstatus.
+    #   @option options [Hash] :env (nil)
+    #     Allows to overwrite env for running command. if key have nil value it
+    #     is deleted from env.
     #
     #   @example
     #     Cheetah.run("tar", "xzf", "foo.tar.gz")
@@ -375,6 +378,7 @@ class << self
 
     def run(*args)
       options = args.last.is_a?(Hash) ? args.pop : {}
+      return changed_env(options, *args) if options[:env]
       options = BUILTIN_DEFAULT_OPTIONS.merge(@default_options).merge(options)
 
       options[:stdin] ||= "" # allow passing nil stdin see issue gh#11
@@ -404,6 +408,17 @@ def run(*args)
 
     private
 
+    def changed_env(options, *args)
+      old_env = ENV.to_hash
+      options = options.dup # do not modify original options
+      env = options.delete(:env)
+      ENV.update(env)
+      args.push(options)
+      run(*args)
+    ensure
+      ENV.replace(old_env)
+    end
+
     # Parts of Cheetah.run
 
     def compute_streamed(options)

spec/cheetah_spec.rb

@@ -757,6 +757,26 @@ def create_command(source, name: "command")
           expect(Cheetah.run("/bin/false", stdout: :capture, allowed_exitstatus: 1)).to eq(["", 1])
         end
       end
+
+      describe "changing environment" do
+        let(:command) do
+          create_command(<<-EOT)
+            echo -n $CHEETAH_TEST
+          EOT
+        end
+
+        it "runs command with given env" do
+          expect(
+            Cheetah.run(command, stdout: :capture, env: { "CHEETAH_TEST" => "OK" })
+          ).to eq "OK"
+        end
+
+        it "do not change env outside call" do
+          ENV["CHEETAH_TEST"] = "OK"
+          Cheetah.run(command, stdout: :capture, env: { "CHEETAH_TEST" => "fail" })
+          expect(ENV["CHEETAH_TEST"]).to eq "OK"
+        end
+      end
     end
   end
 end