Added method to update the IP address for a particular hostname

lib/linux_admin/hosts.rb

@@ -38,6 +38,20 @@ def update_entry(address, hostname, comment = nil)
       end
     end
 
+    # Updates the IP address associated with the entry specified by the hostname
+    # or inserts a new row in the file if there is no entry for that name
+    #
+    # @param hostname [String] the hostname used to find the record to update
+    # @param ip [String] the new address to use for the record
+    def update_ip_for_hostname(host, ip)
+      line_num = @parsed_file.find_path(host).first
+      if line_num
+        @parsed_file[line_num][:address] = ip
+      else
+        update_entry(ip, host)
+      end
+    end
+
     def hostname=(name)
       if cmd?("hostnamectl")
         run!(cmd('hostnamectl'), :params => ['set-hostname', name])

spec/hosts_spec.rb

@@ -32,6 +32,50 @@
     end
   end
 
+  describe "#update_ip_for_hostname" do
+    it "updates an existing entry" do
+      expected_hash = [
+        {:blank => true},
+        {:comment => "Some Comment"},
+        {:address => "127.0.0.1",
+         :hosts   => [
+           "localhost",
+           "localhost.localdomain"
+         ],
+         :comment => "with a comment"
+        },
+        {:address => "192.168.1.10",
+         :hosts   => ["my.domain.local"]
+        }
+      ]
+      @instance.update_ip_for_hostname("my.domain.local", "192.168.1.10")
+      expect(@instance.parsed_file).to eq(expected_hash)
+    end
+
+    it "creates a new entry if none match" do
+      expected_hash = [
+        {:blank => true},
+        {:comment => "Some Comment"},
+        {:address => "127.0.0.1",
+         :hosts   => [
+           "localhost",
+           "localhost.localdomain"
+         ],
+         :comment => "with a comment"
+        },
+        {:address => "127.0.1.1",
+         :hosts   => ["my.domain.local"]
+        },
+        {:address => "192.168.1.10",
+         :hosts   => ["new.domain.local"],
+         :comment => nil
+        }
+      ]
+      @instance.update_ip_for_hostname("new.domain.local", "192.168.1.10")
+      expect(@instance.parsed_file).to eq(expected_hash)
+    end
+  end
+
   describe "#save" do
     before do
       allow(File).to receive(:write)