diff --git a/.idea/kobalt.xml b/.idea/kobalt.xml
index c8751a1..edf71eb 100644
--- a/.idea/kobalt.xml
+++ b/.idea/kobalt.xml
@@ -5,7 +5,7 @@
       <KobaltProjectSettings>
         <option name="autoDownloadKobalt" value="true" />
         <option name="externalProjectPath" value="$PROJECT_DIR$" />
-        <option name="kobaltHome" value="$USER_HOME$/.kobalt/wrapper/dist/kobalt-0.851" />
+        <option name="kobaltHome" value="$USER_HOME$/.kobalt/wrapper/dist/kobalt-0.852" />
         <option name="modules">
           <set>
             <option value="$PROJECT_DIR$" />
diff --git a/README.md b/README.md
index 931eb8c..e6ccafc 100644
--- a/README.md
+++ b/README.md
@@ -6,6 +6,8 @@
 var pl = plugins("net.thauvin.erik:kobalt-exc:")
 
 var p = project {
+    name = "example"
+	
     exec {
        commandLine(listOf("echo", "Hello, World!"))
     }
@@ -14,4 +16,96 @@ var p = project {
 
 ```sh
 ./kobaltw assemble exec
-```
\ No newline at end of file
+```
+
+## CommandLine Directive
+
+```kotlin
+exec {
+    commandLine(listOf("cmd", "/c", "stop.bat"), dir = "../tomcat/bin", os = setOf(Os.WINDOWS))
+    commandLine(listOf("./stop.sh"), dir = "../tomcat/bin", os = setOf(Os.MAC, Os.LINUX))
+    commandLine(listOf("/bin/sh", "-c", "ps aux | grep tomcat"), fail = setOf(Fail.EXIT))
+}
+```
+
+### Parameters
+
+#### args
+
+The full command line including the executable and its parameters.
+
+```kotlin
+exec {
+    commandLine(listOf("ls", "-l"))
+    comamndLine(args = listOf("touch", "README.md"))
+}
+```
+
+#### dir
+
+The working directory for the process. Defaults to the project directory.
+
+```kotlin
+exec {
+    commandLine(listOf("cmd", "/c", "stop.bat"), dir = "../tomcat/bin")
+}
+```
+
+#### os
+
+The operating system(s) to execute the command on. If the current operating system does not match, the command will not be executed.
+
+The following predefined values are available:
+
+Name        | Operating System
+------------|--------------------------------------------------------------------
+Os.FREEBSD  | FreeBSD
+Os.LINUX    | Linux
+Os.MAC      | Apple Macintosh / OS X
+Os.OPENVMS  | OpenVMS
+Os.OS400    | OS/400
+Os.SOLARIS  | Solaris / SunOS
+Os.TANDEM   | Tandem's Non-Stop
+Os.WINDOWS  | Microsoft Windows
+Os.ZOS      | z/OS / OS/390
+
+```kotlin
+exec {
+    commandLine(listOf("cmd", "/c", "stop.cmd"), os = setOf(Os.WINDOWS))
+    commandLine(listOf("./stop.sh"), os = setOf(Os.LINUX, Os.MAC))
+}
+```
+
+#### fail
+
+Specifies whether output to the stderr, stdout and/or an abnormal exit value constitutes a failure.
+
+The following predefined values are available:
+
+Name        | Failure When
+------------|--------------------------------------------------------------------
+Fail.EXIT   | Exit value > 0
+Fail.NORMAL | Exit value > 0 or any output to the standard error stream (stderr).
+Fail.OUTPUT | Any output to the standard output stream (stdout) or stderr.
+Fail.STDERR | Any output to stderr.
+Fail.STDOUT | Any output to stdout.
+Fail.ALL    | Any of the conditions above.
+
+`Fail.NORMAL` is the default value.
+
+```kotlin
+exec {
+    commandLine(listOf("cmd", "/c", "stop.bat"), fail = setOf(Fail.EXIT))
+    commandLine(listOf("./stop.sh"), fail = setOf(Fail.EXIT, Fail.STDOUT))
+}
+```
+
+### Logging / Debugging
+
+```sh
+./kobaltw exec --log 2
+```
+
+
+
+
diff --git a/example/kobalt/src/Build.kt b/example/kobalt/src/Build.kt
index c93d1a5..c4576d5 100644
--- a/example/kobalt/src/Build.kt
+++ b/example/kobalt/src/Build.kt
@@ -40,8 +40,8 @@ val example = project {
     }
 
     exec {
-        commandLine(listOf("cmd", "/c", "echo", "Test Example 1"), os = setOf("Win"))
-		commandLine(args = listOf("ls", "-l"), dir = "../libs", os = setOf("Linux", "Win"))
+        commandLine(listOf("cmd", "/c", "echo", "Test Example 1"), os = setOf(Os.WINDOWS))
+        commandLine(args = listOf("ls", "-l"), dir = "../libs", os = setOf(Os.LINUX, Os.WINDOWS))
     }
 }
 
@@ -49,7 +49,8 @@ val example2 = project {
     name = "example2"
 
     exec {
-		commandLine(listOf("cmd", "/c", "echo", "Test Example 2"), os = setOf("Win"))
+        commandLine(listOf("cmd", "/c", "echo", "Test Example 2"), os = setOf(Os.WINDOWS))
 		commandLine(listOf("echo", "Hello, World!"))
+        commandLine(listOf("sh", "-c", "ps aux | grep bash"), fail = setOf(Fail.EXIT))
     }
 }
\ No newline at end of file
diff --git a/kobalt-exec.iml b/kobalt-exec.iml
index 05598d7..55807a7 100644
--- a/kobalt-exec.iml
+++ b/kobalt-exec.iml
@@ -25,18 +25,9 @@
       </library>
     </orderEntry>
     <orderEntry type="module-library" scope="TEST">
-      <library name="Kobalt: org.apache.ant:ant-launcher:jar:1.7.0">
+      <library name="Kobalt: org.apache.ant:ant:jar:1.7.0">
         <CLASSES>
-          <root url="jar://$USER_HOME$/.kobalt/repository/org/apache/ant/ant-launcher/1.7.0/ant-launcher-1.7.0.jar!/" />
-        </CLASSES>
-        <JAVADOC />
-        <SOURCES />
-      </library>
-    </orderEntry>
-    <orderEntry type="module-library" scope="TEST">
-      <library name="Kobalt: org.beanshell:bsh:jar:2.0b4">
-        <CLASSES>
-          <root url="jar://$USER_HOME$/.kobalt/repository/org/beanshell/bsh/2.0b4/bsh-2.0b4.jar!/" />
+          <root url="jar://$USER_HOME$/.kobalt/repository/org/apache/ant/ant/1.7.0/ant-1.7.0.jar!/" />
         </CLASSES>
         <JAVADOC />
         <SOURCES />
@@ -52,9 +43,18 @@
       </library>
     </orderEntry>
     <orderEntry type="module-library" scope="TEST">
-      <library name="Kobalt: org.apache.ant:ant:jar:1.7.0">
+      <library name="Kobalt: org.beanshell:bsh:jar:2.0b4">
         <CLASSES>
-          <root url="jar://$USER_HOME$/.kobalt/repository/org/apache/ant/ant/1.7.0/ant-1.7.0.jar!/" />
+          <root url="jar://$USER_HOME$/.kobalt/repository/org/beanshell/bsh/2.0b4/bsh-2.0b4.jar!/" />
+        </CLASSES>
+        <JAVADOC />
+        <SOURCES />
+      </library>
+    </orderEntry>
+    <orderEntry type="module-library" scope="TEST">
+      <library name="Kobalt: org.apache.ant:ant-launcher:jar:1.7.0">
+        <CLASSES>
+          <root url="jar://$USER_HOME$/.kobalt/repository/org/apache/ant/ant-launcher/1.7.0/ant-launcher-1.7.0.jar!/" />
         </CLASSES>
         <JAVADOC />
         <SOURCES />
diff --git a/kobalt/wrapper/kobalt-wrapper.properties b/kobalt/wrapper/kobalt-wrapper.properties
index 183e047..c69467d 100644
--- a/kobalt/wrapper/kobalt-wrapper.properties
+++ b/kobalt/wrapper/kobalt-wrapper.properties
@@ -1 +1 @@
-kobalt.version=0.851
\ No newline at end of file
+kobalt.version=0.852
\ No newline at end of file
diff --git a/src/main/kotlin/net/thauvin/erik/kobalt/plugin/exec/ExecPlugin.kt b/src/main/kotlin/net/thauvin/erik/kobalt/plugin/exec/ExecPlugin.kt
index 0ea1fa2..3eb7542 100644
--- a/src/main/kotlin/net/thauvin/erik/kobalt/plugin/exec/ExecPlugin.kt
+++ b/src/main/kotlin/net/thauvin/erik/kobalt/plugin/exec/ExecPlugin.kt
@@ -43,6 +43,7 @@ import java.io.BufferedReader
 import java.io.File
 import java.io.InputStream
 import java.io.InputStreamReader
+import java.util.*
 import java.util.concurrent.TimeUnit
 
 @Singleton
@@ -68,6 +69,47 @@ class ExecPlugin @Inject constructor(val configActor: ConfigActor<ExecConfig>) :
         return result
     }
 
+    private fun matchOs(os: Os): Boolean {
+        val curOs: String = System.getProperty("os.name").toLowerCase(Locale.US)
+        when (os) {
+            Os.WINDOWS -> {
+                return curOs.contains("windows")
+            }
+
+            Os.MAC -> {
+                return (curOs.contains("mac") || curOs.contains("darwin") || curOs.contains("osx"))
+            }
+
+            Os.SOLARIS -> {
+                return (curOs.contains("sunos") || curOs.contains("solaris"))
+            }
+
+            Os.LINUX -> {
+                return curOs.contains("linux")
+            }
+
+            Os.FREEBSD -> {
+                return curOs.contains("freebsd")
+            }
+
+            Os.ZOS -> {
+                return (curOs.contains("z/os") || curOs.contains("os/390"))
+            }
+
+            Os.OPENVMS -> {
+                return curOs.contains("openvms")
+            }
+
+            Os.TANDEM -> {
+                return curOs.contains("nonstop_kernel")
+            }
+
+            Os.OS400 -> {
+                return curOs.contains("os/400")
+            }
+        }
+    }
+
     private fun executeCommands(project: Project, config: ExecConfig): TaskResult {
         var success = true
         val errorMessage = StringBuilder()
@@ -77,9 +119,8 @@ class ExecPlugin @Inject constructor(val configActor: ConfigActor<ExecConfig>) :
             if (wrkDir.isDirectory) {
                 var execute = (os.size == 0)
                 if (!execute) {
-                    val curOs: String = System.getProperty("os.name")
                     for (name in os) {
-                        execute = curOs.startsWith(name, true)
+                        execute = matchOs(name)
                         if (execute) break
                     }
                 }
@@ -147,14 +188,18 @@ enum class Fail() {
     ALL, NORMAL, STDERR, STDOUT, OUTPUT, EXIT
 }
 
-data class CommandLine(var args: List<String> = emptyList(), var dir: String = "", var os: Set<String> = emptySet(),
+enum class Os() {
+    WINDOWS, MAC, SOLARIS, LINUX, FREEBSD, ZOS, OPENVMS, TANDEM, OS400
+}
+
+data class CommandLine(var args: List<String> = emptyList(), var dir: String = "", var os: Set<Os> = emptySet(),
                        var fail: Set<Fail> = setOf(Fail.NORMAL))
 
 @Directive
 class ExecConfig() {
     val commandLines = arrayListOf<CommandLine>()
 
-    fun commandLine(args: List<String> = emptyList(), dir: String = "", os: Set<String> = emptySet(),
+    fun commandLine(args: List<String> = emptyList(), dir: String = "", os: Set<Os> = emptySet(),
                     fail: Set<Fail> = setOf(Fail.NORMAL)) {
         if (args.size > 0) commandLines.add(CommandLine(args, dir, os, fail))
     }