Shell vs. Java: Overcoming theW H I T E PA P E R                     Challenges of Shell Scripting for                    ...
Shell vs. Java: Overcoming the Challenges    of Shell Scripting for UNIX Installations    Introduction                    ...
Shell vs. Java: Overcoming t he Challenges of Shell Script ing for UNIX Installat ions  • Single point of initiation – An ...
Shell vs. Java: Overcoming t he Challenges of Shell Script ing for UNIX Installat ions    Parsing Ability    Shell was wri...
Shell vs. Java: Overcoming t he Challenges of Shell Script ing for UNIX Installat ionsBuilding Multi-Platform Installation...
Shell vs. Java: Overcoming t he Challenges of Shell Script ing for UNIX Installat ions    Components, Features, and Instal...
Shell vs. Java: Overcoming t he Challenges of Shell Script ing for UNIX Installat ionsA LaunchAnywhere launcher is a uniqu...
Shell vs. Java: Overcoming t he Challenges of Shell Script ing for UNIX Installat ions    Custom code development in Java ...
Flexera Software LLC                      Schaumburg                                United Kingdom (Europe,               ...
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Shell vs. Java: Overcoming the Challenges of Shell Scripting for UNIX Installations

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Shell vs. Java: Overcoming the Challenges of Shell Scripting for UNIX Installations

  1. 1. Shell vs. Java: Overcoming theW H I T E PA P E R Challenges of Shell Scripting for UNIX Installations
  2. 2. Shell vs. Java: Overcoming the Challenges of Shell Scripting for UNIX Installations Introduction Web servers, shell-based installations are rarely a viable A shell is a command-line interpreter that takes and executes delivery option. This delivery mechanism becomes more commands, and in doing so, implements a programming difficult when you reanalyze how the tar archive is built. The language commonly referred to as “shell scripting.” Shell configuration management team has to produce a directory scripting is traditionally used by UNIX system administrators structure that will mimic the final destination. to automate the execution of system tasks, but developers also use shell scripts to create enterprise-level software In addition, it is well known that tar-ball installations are installations, and that is where problems occur. not user-friendly to regular users. This is due to the absence of visually guided installations, as is the accepted standard This white paper highlights the major difficulties with for Windows applications. As a result, they often introduce attempting to develop UNIX installations using shell scripts. barriers to user adoption of applications, and may even It focuses on shell scripting as a language and how it is cause problems with the installation and maintenance of used in the context of UNIX installation development. It also the applications. discusses how Java is being used as a successful alternative to shell scripting for enterprise installations. UNIX Installations: The Way They Ought to Be Installations, regardless of the targeted operating system, Finally, this white paper details how the tools in should be easier to implement. The “tar-ball” file archive InstallAnywhere®, the multi-platform installation tool from structure should not be decided upon by the build system. Flexera Software, can help developers overcome the This should be loosely packaged so that the installation can inherent problems with shell scripting and create high- make the final decision on how the final file structure quality multi-platform installations ideal for enterprise should look. environments. The installation technology used should be based on a more UNIX Installations: The Tar-Ball Archive robust language with built-in parsing capabilities for XML, Most UNIX shell-based installations are constructed using Java properties files, and so on. Finally, the installation a “tar-ball” (tar archive) paradigm. A tar file is delivered should give the user the option of running the installation whose contents include a shell script and the files to be in a graphical mode. installed. For the most part the files are stored in a structure mimicking that of their final destination. This potentially Ultimately, customers and installation developers want means that a single copy (cp) command is invoked to copy the same thing, a robust installation system. However, the entire directory to the home directory. All necessary their perspective is different. The customer cares about configurations are done with the help of commands such the final product, whereas the developer cares about as “sed”, “awk”, and so on. The user interface provided is the development environment needed to produce UNIX console only. installations. The following lists are a subset of requirements as demanded by customers and installation developers. By and large, the above scenario is acceptable for simple applications. However, it becomes very hard to follow when For customers: even the most straightforward enterprise installations are • Ease of use – Most customers want an easy way to attempted. If the installation you are attempting to construct interact with an installation, preferably one that is is required to configure application servers, databases, or visually guided, such as those offered by Windows.2 Flexera Software: InstallAnywhere White Paper Series
  3. 3. Shell vs. Java: Overcoming t he Challenges of Shell Script ing for UNIX Installat ions • Single point of initiation – An end user attempting installation and received the same error. Only this time the to invoke your installation should not be confronted error occurs at line 4559. Debugging is not available unless by a plethora of installation options. A single native you type: launcher should suffice. • Native look and feel – It is important that users receive % sh -x install.sh an installation that looks and feels like any other application targeted for that particular operating The above does not yield results that someone with limited system. shell-scripting knowledge can understand. • Get the product installed – The ultimate goal of the installation is to get the product installed and The problem is worsened when the script contains a configured. statement similar to myvar=`cat $1`. If $1 is not initialized, the script will be stuck. Of course, a diligent programmerFor installation developers: doesn’t allow this to happen, but if it does happen, debugging can be a nightmare. • Single point of development – A true cross-platform development platform that would allow the developer Other issues with the script come to light when you consider to maintain a single code base for numerous platforms. the problems associated with localization and permissions • The development environment should use a familiar (“To install, you need admin rightsn”), and dealing with a language, preferably object oriented – To allow nonstandard logging (to install.log) mechanism. extensibility, the installation development tool should enable the developer to extend it. The point of this exercise was to show how difficult it can be • Operating system abstraction – When developing to develop elaborate enterprise installations using shell. cross-platform installations, the developer should focus on product installation and configuration tasks and not Interoperability how each operating system works. Even though shell was never intended for large development, shell scripting is sometimes used to createAnalyzing the Shell Scripting Environment large installation projects, such as enterprise installations.The concept of shell scripting was introduced to help These installations need to directly communicatesystem administrators automate low-level shell commands. configuration settings to the product being installed. ForFor a long time most companies have used shell scripts as shell-based installations, this is done using input files or thedelivery mechanisms (that is, installations), which, for the command line. Error handling, for the most part, is donemost part, worked well. Since shell scripts are delivered using return codes.in clear, readable ASCII, they can potentially exposeimplementations that can pose as security holes. Unfortunately, return codes are not always reliable. Sometimes a command may return 0 when in fact it shouldUnfortunately, that is not the only weakness shell scripting return anything but 0. Extra steps need to be taken to ensureexposes. The following sections highlight why shell scripting reliability, which can turn into unnecessary complex if-does not scale when enterprises attempt to use it as an statements that make interoperability all the more difficult.installation development platform. Sharing CodeThe Development Environment When developing large-scale enterprise installations, youShell is littered with hard-to-understand regular expressions can expect more than one developer to work on the sameand lacks a true integrated development environment (IDE). code. Your plan, of course, is to develop reusable librariesIt often takes a truly senior UNIX developers to properly that can be used across the installation system. However,handle such complex scripting environments. Consider the shell was not designed with that in mind. Shell is for thefollowing syntax: most part used to automate administration tasks such as “empty the temp space” or “manage users.” It was designed CURRENT_USER=`whoami | awk ‘{print $1}’` to deal with low-level tasks, not code sharing. if [ “$CURRENTUSER” != “root” ] && [ “$CURRENT_USER” != “admin” ]; then printf “To install, you need admin Portability rightsn” | tee -a Not all UNIX environments are created equal. Some install.log fi commands work in every UNIX environment; some do not. Sometimes commands such as “pidof” do not exist inIf you take a closer look, you will notice how awkward the environments other than Linux. Furthermore, some utilitiesif-statement really is. If you play with the white-spacing in do not share the same command-line arguments across allthe if-statement, you may receive an error similar to this one: UNIX implementations. Besides, would you like to learn all the command-line options offered by UNIX commands such ./install.sh: line 2: [CURRENT_USER: command not found] as “ls”? To account for portability, a great deal of code must be written.Although this may not seem like a big problem, imaginewhat would happen if someone in the field ran yourFlexera Software: InstallAnywhere White Paper Series 3
  4. 4. Shell vs. Java: Overcoming t he Challenges of Shell Script ing for UNIX Installat ions Parsing Ability Shell was written long before SGML technologies such as public String getInstallStatusMessage( ) { return XML were available. Therefore, its abilities for parsing such “Computing time stamp...”; } formats are based on regular expressions. For the most part, regular expressions are hard to write and even harder to public void uninstall(UninstallerProxy up) { /* do nothing debug. To consider writing regular expressions for parsing on uninstall */ } XML would put you in the business of building XML parsers public String getUninstallStatusMessage( ) { return “...”; } from scratch. Modern languages such as Java and C++ } have XML parsers built-in. First and foremost, the above code is standard Java code. Parsing becomes more of a problem when unknown formats In addition to being able to use standard Java functionality, are met. New regular expressions must be built, or you Java code can use JNI to call in to native code. The could write a native executable using C/C++ to do the job. interesting thing about JNI is the fact that as far as the Once again, interoperability becomes questionable. Java developer is concerned, the JNI call is just another Java call. The Linux Factor With the introduction of Linux, a large number of non- Worth noticing is also the exception handling offered by UNIX users entered the UNIX arena. From a strategic Java. Logging is another powerful Java feature. To facilitate point of view, it gives a large number of users the chance readability, logging information can be categorized by to diversify. On the other hand, most of these new users severity and the output can be formatted as XML, which in come from GUI-driven operating systems, and they want turn can be transformed into HTML so that customers can everything be done with graphical tools. But shell-based view install logs in a readable format. installations are made to be console-driven – no graphical interface. Java has emerged as a very popular technology, and for good reasons. Most educators have embraced Java as Mac OS X their teaching language of choice, creating a large pool Mac OS X is further proof that UNIX is becoming more of Java developers. The attractiveness of Java as a “write accepted as a graphical operating system. Besides making once, run everywhere” language has certainly been another Mac OS X the most optimized UNIX environment to run contributing factor to its popularity. Java, Apple has made Java an integral part of Mac OS X, which is good news if your strategy is to create Java-based Another strong supporting argument for Java-based installations. But shell-based installations must once again installations is that numerous companies deploy application take a back seat. servers such as IBM® WebSphere®, BEA® WebLogic®, Sun® Java Enterprise System, or JBoss. For scalability and Java-Based Installations reliability purposes, these are mostly deployed on the UNIX If not shell scripting, what then is a feasible alternative platform and are Java-based. technology for developing cross-platform installations? What about Java? Its “write once, run everywhere” makes Most application servers expose Java configuration APIs. it an ideal technology for targeting platforms such as UNIX. This allows for a seamless integration strategy that can Java transforms the installation development into a more ultimately give users an out-of-the-box delivery solution. The robust environment. interesting point here is that “write once, run everywhere” becomes an attainable reality. To appreciate the power of Java to extend an installation, consider an example. The following is a simple Java class As an alternative to shell scripting, however, Java requires that computes a time stamp and stores the result in a custom additional help before it can be considered as a logical InstallAnywhere variable. successor. A reliable, user-friendly Windows-like setup experience would be a great thing to have for UNIX import com.zerog.ia.api.pub.*; developers. The ability to target UNIX and Windows import java.util.*; platforms with a Java-based application install would be even better, especially given how difficult it is to accomplish public class GenerateTimeStamp extends this with shell scripting. CustomCodeAction { For the developer with lots of experience with tar-balls and public void install(InstallerProxy ip) cryptic script commands, any alternative needs to offer { clear and compelling benefits. The balance of this paper // compute time stamp with Java... will offer just such an argument, based on the capabilities String now = new Date( ).toString( ); of InstallAnywhere from Flexera Software. // ...and set a custom variable to the value ip.setVariable(“$NOW$”, now); }4 Flexera Software: InstallAnywhere White Paper Series
  5. 5. Shell vs. Java: Overcoming t he Challenges of Shell Script ing for UNIX Installat ionsBuilding Multi-Platform Installations with graphical interface, which allows developers to manageInstallAnywhere all aspects of their installer project. All the features ofInstallAnywhere from Flexera Software provides an out-of- InstallAnywhere are available in this easy to use integratedthe-box Java-based installation solution. Developing cross- development environment.platform installations with Java and InstallAnywhere’s multi-platform installation IDE provides many benefits, including Advanced Designer Tasksmaking it easy to: The Advanced Designer is divided into tasks that are represented by tabs found along the left-hand side of the • Tightly integrate installation development into the window. Each of the following tabs represents tasks and development department settings specific to each installation project: • Conceal code so that proprietary implementations are kept safe • Project: Settings related to your specific project. • Create installations that can be extended and These include general settings, file settings, and developed using Java technologies localization settings. • Installer UI: Set the look and feel for the installer by Learn More about InstallAnywhere adding background images, billboards, and other If you wish to learn more about the capabilities of graphical components. InstallAnywhere, please visit the Flexera Software Web • Organization: Manages Install Sets, Features, site at www.flexerasoftware.com/installanywhere. Components, and Merge Modules. • Pre-Install: An ordered sequence of panels and actions that occur before file installation.With InstallAnywhere, developers can build installers for all • Install: Manage File installation tree and installsupported platforms from a single project. InstallAnywhere’s time actions.capabilities (highlighted below) make it the ideal tool for • Post-Install: An ordered sequence of panels and actionsquickly developing industrial-strength installers. that occur after file installation. • Pre-Uninstall: An ordered sequence of panels andRapid Prototyping with the Project Wizard actions that occur before file uninstallation.Developers can build their first installer in less than five • Post-Uninstall: An ordered sequence of panels andminutes with InstallAnywhere’s six-step Project Wizard. This actions that occur after file uninstallation.intuitive design tool also sets the class path and finds the • Build: Manage build settings, including bundling of amain class for a Java application automatically. When you Java Virtual Machine.complete the Project Wizard steps, the result is an installerproject that targets a number of major operating systems. Each Advanced Designer task contains sub-tabs that offer greater fine-tuning of InstallAnywhere’s features.This working prototype is inline with management demandsthat prototypes be produced early in the developmentprocess. The development process demands that theinstallation be integrated early so that testing can beperformed in a more realistic environment. Action-Based Installers Actions, which represent the operations the installer performs, are the fundamental elements of InstallAnywhere installers. InstallAnywhere supports an extensible action architecture that provides the ability to perform additional operations during installation, such as installing files and folders, creating shortcuts, executing custom code, or extracting the contents of a compressed file. SomeThis, for the most part, means that the installation should frequently used actions include Install File, Create Folder,have the capability to run in graphical mode and have a Create Alias, Link, Shortcut, Execute Target File, Executeconsistent look and feel regardless of the operating system. Command, and Expand Archive.InstallAnywhere contains many tools that make rapidprototyping a reality.Customizing Projects in the Advanced DesignerThe InstallAnywhere Advanced Designer has an intuitive,Flexera Software: InstallAnywhere White Paper Series 5
  6. 6. Shell vs. Java: Overcoming t he Challenges of Shell Script ing for UNIX Installat ions Components, Features, and Install Sets Components, features, and install sets are organizational concepts in the InstallAnywhere IDE. They allow installer developers to add structure to the files and actions their installers employ and determine what feature choices end users have during the install. Components are an organization unit installer developers Build and Try can use to group files and actions; however, components InstallAnywhere users can quickly examine the results of are internal organization units that are never shown to the their project changes by building installers from the project end user. Conversely, features can group one or more and running the resulting installer with the click of a button. components, files, and actions into combinations from In addition, InstallAnywhere includes several built in features which the installer end users can choose. And groups of for previewing and debugging your installers and installer features can be combined into install sets—a convention panels. that allows end users to choose options like Minimal, Typical, or Full Install. While developers working with relatively simple installers can rely on InstallAnywhere to generate basic components, features, and install sets automatically, more advanced developers take control of components, features, and install sets to organize their installer resources in the Get User Input Panels Advanced Designer. InstallAnywhere provides many panels for displaying information to the user and collecting user information. Moreover, InstallAnywhere includes the Get User Input - Simple and Get User Input - Advanced panel actions. These actions enable you to build custom panels by inserting text- display and user-input controls into the Get User Input panel. InstallAnywhere provides the architecture to capture the user input from these panels to InstallAnywhere variables. For requirements that exceed the Get User Input panel’s features, you can code custom panels that share the dimensions, images, navigation buttons, and other elements used by built-in panels. Rules and Variables InstallAnywhere keeps track of dynamic values using variables. Almost every dynamic value in InstallAnywhere is represented by an InstallAnywhere variable. Variables may be modified or accessed in order to affect the design or output of an installer; they can also be modified during the progress of the installer in order to change the installer’s behavior. InstallAnywhere uses variable-based Boolean rules to control most aspects of installer behavior. Rules can be applied to any action within the InstallAnywhere installer, as well as to organizational units such as Install Sets, Features, LaunchAnywhere Launchers and Components. Rules commonly direct the execution Create launchers that look and behave like the operating of platform-specific actions on the target system, but they system your installation is running on. Your end users are may check other conditions such as system architecture, file accustomed to a particular behavior. Windows users are and folder attributes, and user-chosen language. Rules can quite familiar with the ubiquitous installer.exe concept. also be used to compare the values of two InstallAnywhere InstallAnywhere LaunchAnywhere launchers extend that variables, match a regular expression, or to execute a philosophy to all of its supported platforms. custom coded rule. (InstallAnywhere Enterprise edition also includes rules specific to System i (i5/OS).)6 Flexera Software: InstallAnywhere White Paper Series
  7. 7. Shell vs. Java: Overcoming t he Challenges of Shell Script ing for UNIX Installat ionsA LaunchAnywhere launcher is a unique executable custom panels, custom consoles, and custom rules thatthat launches a Java application on Windows, UNIX interact with and extend InstallAnywhere functionality.(including Solaris, Linux, HP-UX, AIX, BSD, and others),and Mac OS X platforms. On Windows, LaunchAnywhere Custom Dialog Boxestechnology creates double-clickable icons that invoke a InstallAnywhere provides many built-in dialog boxes forJava application. For Mac OS X, it generates application displaying information to the user and collecting userbundles. On UNIX platforms, end users type a simple information. Moreover, InstallAnywhere’s Get User Inputcommand to launch the application. panels enable you to build up custom dialog boxes by inserting text-display and user-input components into aLaunchAnywhere technology sets the classpath, redirects standard dialog box frame. For more sophisticated user-stdout and stderr, passes in system properties and command- interface requirements, you can create custom panels thatline parameters, and performs other configuration functions. share the dimensions, images, navigation buttons, andFor graphical users a Web-based applet installation is also other elements used by built-in panels.available. This further simplifies the distribution model ofyour product. Shell Revisited As mentioned earlier, shell scripting was intended for system administration. To that end, some scripts are worth keeping. InstallAnywhere facilitates launching existing shell scripts (even the ones that take command line arguments). Since most shell scripts are processed through /bin/sh (the first line in a shell script, the shebang—i.e., #!/bin/sh—tells you who is going to process the script), shell scripts can also be launched through Runtime.exec. This command returns a Process object, which in turn can return the exit value from the sh process. Powered by Java InstallAnywhere is powered by Java. Java is a full-fledged, object-oriented language. Its cross-platform capabilities make it the perfect engine for InstallAnywhere.Customizing and Extending InstallAnywhereAdvanced installer developers or development teams that Besides the common tasks supplied by InstallAnywhere, youneed to build complex installers can take advantage of a might want to add custom tasks that do not fit the ordinary.host of enterprise-strength features: Since InstallAnywhere is powered by Java, you can extend its functionality in a number of ways. • Merge Modules: Essentially installer sub-projects that can be created independently of one another and • Create your own custom Java plug-ins: InstallAnywhere later merged together, merge module are reusable enables you to create custom actions written in Java. collections of installation functionality. A Merge You can refer to your custom code in a single project, Module is just like an installer, complete with features, or package it as an InstallAnywhere plug-in that can be components, panels, actions, and files. However, a used in multiple projects. Merge Module cannot be installed without being part • Use InstallAnywhere services: In addition to being able of an InstallAnywhere project; instead, use Merge to call Java code from your custom code actions, you Modules to include the functionality of one installer can call methods from InstallAnywhere services. These within another installer. services extend Java functionality with underlying • Support for Deployment to Application Servers and native code. Example services are the System Utility Database Servers: InstallAnywhere supports installers Service, for working with environment variables that target application servers (such as Geronimo, and system startup commands; the Security Service, JBoss, Resin, Sun Application Server, Tomcat, for working with users and groups; and the Win32 WebLogic, and WebSphere) and database servers and Win32 Registry Services, for programmatically (such as MySQL, Oracle, MS SQL Server, and DB2). manipulating Windows services and the Windows • Team Development Features: InstallAnywhere supports registry. team-based installer development with source paths. • Java Native Interface (JNI): Although Java is a powerful Source paths allow developers to reference file language, some operating system APIs have not been resources using variable paths instead of absolute mapped into the core language. JNI is intended to paths. This allows team members to share a project file breach that gap. If necessary, you can implement even when file resources are located at different paths custom functionality in a native library (a Windows on their development systems. DLL or UNIX shared library, for example) and call the • Custom Code: With InstallAnywhere’s API, developers native code from an InstallAnywhere custom code can write custom Java code that runs in the same action. Java VM as InstallAnywhere, creating custom actions,Flexera Software: InstallAnywhere White Paper Series 7
  8. 8. Shell vs. Java: Overcoming t he Challenges of Shell Script ing for UNIX Installat ions Custom code development in Java is enhanced further when you consider the following: • XML parsing: Java provides out-of-the-box XML parsing through standard parsing technologies such as DOM or SAX. • Use any Java IDE: When writing InstallAnywhere custom code, you can use your own Java IDE. • Unit testing with JUnit: JUnit is a popular regression- testing framework, and InstallAnywhere provides classes for integrating with JUnit. • Coding standards: Create or extend existing common coding standards to accommodate the development of InstallAnywhere custom code. Summary Though shell scripting is being criticized for its installation development capabilities, this white paper considers shell scripting a sound technology for UNIX system administration. But for software development, shell scripts lack the robustness needed to create platform independent installations. Java as a technology has matured to the point that creating Java-based installations has become the preferred method. Furthermore, technologies such as JDBC, CORBA, JNDI, and RMI, make Java-based installations the better candidate for targeting platforms such as UNIX. Begin a Free Evaluation of InstallAnywhere You can download a free trial version of InstallAnywhere from the Flexera Software Web site at: www.flexerasoftware.com/installanywhere/eval. Want to learn more best practices for building quality installations? Join an InstallAnywhere training class – visit www.flexerasoftware.com/training for available classes.8 Flexera Software: InstallAnywhere White Paper Series
  9. 9. Flexera Software LLC Schaumburg United Kingdom (Europe, Japan (Asia, For more office locations visit:1000 East Woodfield Road, (Global Headquarters): Middle East Headquarters): Pacific Headquarters): www.flexerasoftware.comSuite 400 +1 800-809-5659 +44 870-871-1111 +81 3-4360-8291Schaumburg, IL 60173 USA +44 870-873-6300Copyright © 2011 Flexera Software LLC. All other brand and product names mentioned herein may be the trademarks and registered trademarks of their respective owners. IA_WP_Shell_Oct11

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