Executing Programs

This section describes how to execute programs from the command line. You can use this information to run programs that you obtain from the recipes distribution or that you write yourself. The first set of instructions applies to scripts written in Perl, Ruby, PHP, or Python. A second set of instructions applies to Java programs.

The example programs can be found in the progdemo directory of the recipes distribution.

Executing Perl, Ruby, PHP, or Python Scripts

The following discussion shows how to execute scripts, using Perl for the examples. However, the principles are similar for Ruby, PHP, and Python scripts.

Begin with an example script named perldemo.pl that consists of a simple print statement:

print "I am a Perl program.\n"; 

A script-execution method that works on any platform is to invoke the perl program and tell it the name of the script to run:

% perl perldemo.pl I am a Perl program. 

For a script written in another language, invoke the ruby, php, or python program.

It's also possible to set up a script so that it is directly executable. The procedure is different for Unix and Windows. Both procedures are described here.

On Unix, to make a script directly executable, include a line at the top of the file that begins with #! and that specifies the pathname of the program that should execute the script. Here is a script named perldemo2.pl with a #! line that names the perl program (if perl has a different location on your system, you'll need to change the pathname):

#!/usr/bin/perl print "I am a Perl program.\n"; 

Next, enable the executable access mode with chmod +x:

% chmod +x perldemo2.pl             

At this point, the script can be run the same way as its earlier counterpart (that is, you can use perl perldemo2.pl), but now you should also be able to execute it by entering just its name. However, assuming that the script is located in your current directory, your shell might not find it. The shell searches for programs in the directories named in your PATH environment variable, but for security reasons, the search path for Unix shells often is deliberately set not to include the current directory (.). In that case, include a leading path of ./ to explicitly indicate the script's location:

% ./perldemo2.pl I am a Perl program. 

If you install the script by copying it to a directory that is named in your PATH setting, the leading path is unnecessary when you invoke the script.

On Windows, the procedure for making scripts executable is somewhat different. chmod is not used. Instead, programs are treated as executable based on their filename extensions (such as .exe or .bat). Windows allows you to set up filename associations such that a program can be associated with filenames that end with a particular suffix. This means that you can set up associations so that Perl, Ruby, PHP, or Python are used to execute files with names that end in .pl, .rb, .php, or .py, respectively. (In fact, the installer for a given language might even create the association for you.) Then you can invoke a script with a given extension directly from the command line without naming its language interpreter:

C:\> perldemo.pl I am a Perl program. 

No leading path is needed to invoke a script that is located in the current directory because the Windows command interpreter includes that directory in its search path by default.

Keep the preceding principles in mind when you run scripts from within a directory of the recipes distribution. For example, if you are currently located in the metadata directory of the distribution and you want to execute the get_server_version.rb Ruby script, you can do so with either of these commands on Unix:

% ruby get_server_version.rb % ./get_server_version.rb             

On Windows, you can use either of these commands:

C:\> ruby get_server_version.rb C:\> get_server_version.rb             

Compiling and Executing Java Programs

Java programming requires a software development kit (SDK). If a Java SDK is not already installed on your system, obtain one and install it. For Solaris, Linux, and Windows, Java SDKs are available at java.sun.com. For Mac OS X, current versions come with an SDK; for earlier versions that do not, javac and other support needed for building Java applications is included in the Developer Tools distribution available at connect.apple.com.

After verifying that a Java SDK is installed, set the JAVA_HOME environment variable if it is not already set. Its value should be the pathname of the directory where the SDK is installed. If the SDK installation directory is /usr/local/java/jdk on Unix or C:\jdk on Windows, set JAVA_HOME as follows:

• For a shell in the Bourne shell family (sh, bash, ksh):

  export JAVA_HOME=/usr/local/java/jdk 

  
  

  If you are using the original Bourne shell, sh, you may need to split this into two commands:

  JAVA_HOME=/usr/local/java/jdk export JAVA_HOME

  
  

• For a shell in the C shell family (csh, tcsh):

  setenv JAVA_HOME=/usr/local/java/jdk 

  
  

• For Windows, get to the Environment Variables window as described earlier in "Setting Environment Variables," and set JAVA_HOME to this value:

  C:\jdk 

  
  

Adjust the instructions for the pathname actually used on your system.

With a Java SDK in place and JAVA_HOME set, you should be able to compile and run Java programs. Here is a sample program:

public class JavaDemo {   public static void main (String[] args)   {     System.out.println ("I am a Java program.");   } } 

The class statement indicates the program's name, which in this case is JavaDemo. The name of the file containing the program should match this name and include a .java extension, so the filename for the program is JavaDemo.java. Compile the program using javac:

% javac JavaDemo.java             

If you prefer a different Java compiler, just substitute its name. For example, if you'd rather use Jikes, compile the file like this instead:

% jikes JavaDemo.java             

The Java compiler generates compiled byte code to produce a class file named JavaDemo.class. Use the java program to run the class file (specified without the .class extension):

% java JavaDemo I am a Java program. 

To compile and run MySQL-based programs written in Java, you'll need the MySQL Connector/J JDBC driver (Section 2.1). If Java cannot find the driver, you'll need to set your CLASSPATH environment variable. Its value should include at least your current directory (.) and the pathname of the MySQL Connector/J driver. If the driver has a pathname of /usr/local/lib/java/lib/mysql-connector-java-bin.jar (Unix) or C:\Java\lib\mysql-connector-java-bin.jar (Windows), set CLASSPATH as follows:

• For a shell in the Bourne shell family (sh, bash, ksh):

  export CLASSPATH=.:/usr/local/lib/java/lib/mysql-connector-java-bin.jar 

  
  

• For a shell in the C shell family (csh, tcsh):

  setenv CLASSPATH .:/usr/local/lib/java/lib/mysql-connector-java-bin.jar 

  
  

• For Windows, get to the Environment Variables window as described earlier in "Setting Environment Variables," and set CLASSPATH to this value:

  .;C:\Java\lib\mysql-connector-java-bin.jar 

  
  

Adjust the instructions for the pathname actually used on your system. You might also need to add other class directories or libraries to your CLASSPATH setting. The specifics depend on how your system is set up.