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Chapter 96. Exec Component

Available as of Camel version 2.3

The exec component can be used to execute system commands.

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

<dependency>
  <groupId>org.apache.camel</groupId>
  <artifactId>camel-exec</artifactId>
  <version>${camel-version}</version>
</dependency>
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where ${camel-version} must be replaced by the actual version of Camel (2.3.0 or higher).

96.2. URI format
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exec://executable[?options]
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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.

96.3. URI options
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The Exec component has no options.

The Exec endpoint is configured using URI syntax: 

exec:executable
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with the following path and query parameters:

96.3.1. Path Parameters (1 parameters):
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Expand
NameDescriptionDefaultType

executable

Required Sets the executable to be executed. The executable must not be empty or null.

 

String

96.3.2. Query Parameters (8 parameters):
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Expand
NameDescriptionDefaultType

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

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

Expand
NameTypeMessageDescription

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.

96.5. Message body
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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, 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 type converters for convenience:

Expand
FromTo

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 usage examples below.

96.6. Usage examples
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96.6.1. Executing word count (Linux)
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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. 

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
     }
});
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96.6.2. Executing java
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The example below executes java with 2 arguments: -server and -version, provided that java is in the system path. 

from("direct:exec")
.to("exec:java?args=-server -version")
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The example below executes java in c:\temp with 3 arguments: -server, -version and the sytem property user.name. 

from("direct:exec")
.to("exec:c:/program files/jdk/bin/java?args=-server -version -Duser.name=Camel&workingDir=c:/temp")
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96.6.3. Executing Ant scripts
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The following example executes 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. 

from("direct:exec")
.to("exec:ant.bat?args=-f CamelExecBuildFile.xml")
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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. 

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
     }
  });
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96.6.4. Executing echo (Windows)
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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. 

from("direct:exec").to("exec:cmd?args=/C echo echoString")
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96.7. See Also
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  • Configuring Camel
  • Component
  • Endpoint
  • Getting Started
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