components/camel-exec/src/main/docs/exec-component.adoc

## Exec Component

*Available as of Camel version 2.3*

The `exec` component can be used to execute system commands.

### Dependencies

Maven users need to add the following dependency to their `pom.xml`

[source,xml]
-------------------------------------
<dependency>
  <groupId>org.apache.camel</groupId>
  <artifactId>camel-exec</artifactId>
  <version>${camel-version}</version>
</dependency>
-------------------------------------

where `${camel-version`} must be replaced by the actual version of Camel
(2.3.0 or higher).

### URI format

[source,xml]
---------------------------
exec://executable[?options]
---------------------------

where `executable` is the name, or file path, of the system command that
will be executed. If executable name is used (e.g. `exec:java`), the
executable must in the system path.

### URI options

// component options: START
The Exec component has no options.
// component options: END

// endpoint options: START
The Exec endpoint is configured using URI syntax:

    exec:executable

with the following path and query parameters:

#### Path Parameters (1 parameters):

[width="100%",cols="2,5,^1,2",options="header"]
|=======================================================================
| Name | Description | Default | Type
| **executable** | *Required* Sets the executable to be executed. The executable must not be empty or null. |  | String
|=======================================================================

#### Query Parameters (8 parameters):

[width="100%",cols="2,5,^1,2",options="header"]
|=======================================================================
| Name | Description | Default | Type
| **args** (producer) | The arguments may be one or many whitespace-separated tokens. |  | String
| **binding** (producer) | A reference to a org.apache.commons.exec.ExecBinding in the Registry. |  | ExecBinding
| **commandExecutor** (producer) | A reference to a org.apache.commons.exec.ExecCommandExecutor in the Registry that customizes the command execution. The default command executor utilizes the commons-exec library which adds a shutdown hook for every executed command. |  | ExecCommandExecutor
| **outFile** (producer) | The name of a file created by the executable that should be considered as its output. If no outFile is set the standard output (stdout) of the executable will be used instead. |  | String
| **timeout** (producer) | The timeout in milliseconds after which the executable should be terminated. If execution has not completed within the timeout the component will send a termination request. |  | long
| **useStderrOnEmptyStdout** (producer) | A boolean indicating that when stdout is empty this component will populate the Camel Message Body with stderr. This behavior is disabled (false) by default. | false | boolean
| **workingDir** (producer) | The directory in which the command should be executed. If null the working directory of the current process will be used. |  | String
| **synchronous** (advanced) | Sets whether synchronous processing should be strictly used or Camel is allowed to use asynchronous processing (if supported). | false | boolean
|=======================================================================
// endpoint options: END

### Message headers

The supported headers are defined in
`org.apache.camel.component.exec.ExecBinding`.

[width="100%",cols="10%,10%,10%,70%",options="header",]
|=======================================================================
|Name |Type |Message |Description

|`ExecBinding.EXEC_COMMAND_EXECUTABLE` |`String` |`in` |The name of the system command that will be executed. Overrides
`executable` in the URI.

|`ExecBinding.EXEC_COMMAND_ARGS` |`java.util.List<String>` |`in` |Command-line arguments to pass to the executed process. The arguments
are used literally - no quoting is applied. Overrides any existing
`args` in the URI.

|`ExecBinding.EXEC_COMMAND_ARGS` |`String`| `in` |*Camel 2.5:* The arguments of the executable as a Single string where
each argument is whitespace separated (see `args` in URI option). The
arguments are used literally, no quoting is applied. Overrides any
existing `args` in the URI.

|`ExecBinding.EXEC_COMMAND_OUT_FILE` |`String` |`in` |The name of a file, created by the executable, that should be considered
as its output. Overrides any existing `outFile` in the URI.

|`ExecBinding.EXEC_COMMAND_TIMEOUT` |`long` |`in` |The timeout, in milliseconds, after which the executable should be
terminated. Overrides any existing `timeout` in the URI.

|`ExecBinding.EXEC_COMMAND_WORKING_DIR` |`String` |`in` |The directory in which the command should be executed. Overrides any
existing `workingDir` in the URI.

|`ExecBinding.EXEC_EXIT_VALUE` |`int` |`out` |The value of this header is the _exit value_ of the executable. Non-zero
exit values typically indicate abnormal termination. Note that the exit
value is OS-dependent.

|`ExecBinding.EXEC_STDERR` |`java.io.InputStream` |`out` |The value of this header points to the standard error stream (stderr) of
the executable. If no stderr is written, the value is `null`.

|`ExecBinding.EXEC_USE_STDERR_ON_EMPTY_STDOUT` |`boolean` |`in` |Indicates that when `stdout` is empty, this component will populate the
Camel Message Body with `stderr`. This behavior is disabled (`false`) by
default.
|=======================================================================

### Message body

If the `Exec` component receives an `in` message body that is
convertible to `java.io.InputStream`, it is used to feed input to the
executable via its stdin. After execution,
http://camel.apache.org/exchange.html[the message body] is the result of
the execution,- that is, an
`org.apache.camel.components.exec.ExecResult` instance containing the
stdout, stderr, exit value, and out file. This component supports the
following `ExecResult` http://camel.apache.org/type-converter.html[type
converters] for convenience:

[width="100%",cols="50%,50%",options="header",]
|=======================================================================
|From |To

|`ExecResult` |`java.io.InputStream`

|`ExecResult` |`String`

|`ExecResult` |`byte []`

|`ExecResult` |`org.w3c.dom.Document`
|=======================================================================

If an out file is specified (in the endpoint via `outFile` or the
message headers via `ExecBinding.EXEC_COMMAND_OUT_FILE`), converters
will return the content of the out file. If no out file is used, then
this component will convert the stdout of the process to the target
type. For more details, please refer to the link:exec.html[usage
examples] below.

### Usage examples

#### Executing word count (Linux)

The example below executes `wc` (word count, Linux) to count the words
in file `/usr/share/dict/words`. The word count (output) is written to
the standard output stream of `wc`.

[source,java]
--------------------------------------------------------------------------------------
from("direct:exec")
.to("exec:wc?args=--words /usr/share/dict/words")
.process(new Processor() {
     public void process(Exchange exchange) throws Exception {
       // By default, the body is ExecResult instance
       assertIsInstanceOf(ExecResult.class, exchange.getIn().getBody());
       // Use the Camel Exec String type converter to convert the ExecResult to String
       // In this case, the stdout is considered as output
       String wordCountOutput = exchange.getIn().getBody(String.class);
       // do something with the word count
     }
});
--------------------------------------------------------------------------------------

#### Executing `java`

The example below executes `java` with 2 arguments: `-server` and
`-version`, provided that `java` is in the system path.

[source,java]
--------------------------------------
from("direct:exec")
.to("exec:java?args=-server -version")
--------------------------------------

The example below executes `java` in `c:\temp` with 3 arguments:
`-server`, `-version` and the sytem property `user.name`.

[source,java]
----------------------------------------------------------------------------------------------------
from("direct:exec")
.to("exec:c:/program files/jdk/bin/java?args=-server -version -Duser.name=Camel&workingDir=c:/temp")
----------------------------------------------------------------------------------------------------

#### Executing Ant scripts

The following example executes http://ant.apache.org/[Apache Ant]
(Windows only) with the build file `CamelExecBuildFile.xml`, provided
that `ant.bat` is in the system path, and that `CamelExecBuildFile.xml`
is in the current directory.

[source,java]
--------------------------------------------------
from("direct:exec")
.to("exec:ant.bat?args=-f CamelExecBuildFile.xml")
--------------------------------------------------

In the next example, the `ant.bat` command redirects its output to
`CamelExecOutFile.txt` with `-l`. The file `CamelExecOutFile.txt` is
used as the out file with `outFile=CamelExecOutFile.txt`. The example
assumes that `ant.bat` is in the system path, and that
`CamelExecBuildFile.xml` is in the current directory.

[source,java]
-------------------------------------------------------------------------------------------------------
from("direct:exec")
.to("exec:ant.bat?args=-f CamelExecBuildFile.xml -l CamelExecOutFile.txt&outFile=CamelExecOutFile.txt")
.process(new Processor() {
     public void process(Exchange exchange) throws Exception {
        InputStream outFile = exchange.getIn().getBody(InputStream.class);
        assertIsInstanceOf(InputStream.class, outFile);
        // do something with the out file here
     }
  });
-------------------------------------------------------------------------------------------------------

#### Executing `echo` (Windows)

Commands such as `echo` and `dir` can be executed only with the command
interpreter of the operating system. This example shows how to execute
such a command - `echo` - in Windows.

[source,java]
----------------------------------------------------------
from("direct:exec").to("exec:cmd?args=/C echo echoString")
----------------------------------------------------------

### See Also

* link:configuring-camel.html[Configuring Camel]
* link:component.html[Component]
* link:endpoint.html[Endpoint]
* link:getting-started.html[Getting Started]