Unit 1-introduction to scripts

Unit 1-introduction to scripts

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  BY SANA MATEEN 6/13/2016 1Introductionto scripts and scripting
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  INTRODUCTION TO SCRIPTSAND SCRIPTING  Script is a program written for special runtime environment that automate the execution of tasks.  Scripting is the action of writing scripts using scripting language.  Scripting Language are used to extend the functionality of software . For example enhancing web pages by providing dynamic content.  They are designed to automate frequently used task that usually involve calling or passing commands to external program. Examples: 1. PERL- PRACTICAL EXTRACTION AND REPORT LANGUAGE 2. PHP-Hypertext Preprocessor(Personal Home Page) 3. TCL-Tool Command Language and PYTHON TCL 6/13/2016 2Introduction to scripts and scripting
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  SCRIPTING VS. PROGRAMMING:IS THERE A DIFFERENCE? Scripting Programming  Scripts are interpreted . It means they are processed from scratch every time you run them.  Programs are executed. Problems addressed by Scripting language  Building applications from off-the-shelf components.  Example: Use of Visual Basic to develop GUI using prebuilt Visual Controls.  Controlling applications that have a programmable interface(protocols to be followed while building a software).  Speed of development is more important than runtime efficiency. 6/13/2016 3Introduction to scripts and scripting
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  ORIGIN OF SCRIPTING The UNIX O.S developers coined the term shellscript for sequence of commands that were read from a file and followed in sequence.  Script is a file that is intended to be executed directly rather than being compiled.  Examples of scripts with respect to unix system are:  AWK: This utility reads the standard input line by line and takes an action on part of entire line.  These actions are specified in awk script that consist of list of instructions.  Perl: is a scripting language developed by Larry Wall, especially designed for text processing.  Though Perl is not officially an acronym but many times it is used as it stands for Practical Extraction and Report Language.  It runs on a variety of platforms, such as Windows, Mac OS, and the various versions of UNIX. 6/13/2016 4Introduction to scripts and scripting
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  ORIGIN OF SCRIPTING In DOS(Disk Operating System), use of dial up connection to remote system require scripts that automate the sequence of operation required to establish a connection to remote system.  Use rasphone( Remote Access Phonebook) command.  Another occurrence of script was in Apple Macintosh HyperCard Application, which is one of the Hypertext system. 6/13/2016 5Introduction to scripts and scripting
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  SCRIPTING TODAY  Scriptingallows application to be developed much faster than traditional methods allow.  We can use it to manipulate,customize,automate the facilities of existing system.  Eg: Use of client side scripting and Dynamic HTML to create interactive and feature rich enhanced web pages.  Using Scripting Language with its rich functionality .These are used by UNIX admin for System maintenance work, like managing user permissions.  Windows system admin adopt Perl for their work.  Apache web server has an embedded Perl interpreter for CGI scripts 6/13/2016 6Introduction to scripts and scripting
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  CGI SCRIPT ISAPITECHNOLOGY  CGI stands for Common Gateway Interface.  It defines a standard way in which information may be passed to and from the browser and server.  CGI scripts can be written using PERL.  ISAPI stands for Internet Server Application Program Interface technology . It is set of window program calls that let you write a web server application that will run faster than CGI.  We can create Dynamic Link Library application file using this technology.  We can write an ISAPI script in any language that will create an executable object on your system. For example, C++, Visual Basic, or Perl script on Windows. 6/13/2016 7Introduction to scripts and scripting
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  CHARACTERISTICS OF SCRIPTINGLANGUAGE  Integrated Compile and Run Scripting Language behave as if they were interpreted. They are often an interactive, experimental activity that doesn’t fit well with the “edit-compile- link-run” cycle of conventional programming. A few Scripting Languages like Unix Shell and TCL(Tool Command Language) version 7 are indeed implemented as strict interpreters. However most of the languages in current use opt for hybrid technique which involve compiling to an intermediate form which is then interpreted.  Low Overhead and ease of use Based on the usage variables can be declared and initialized . Later focus was on explicit variable declaration, which requires that you declare every variable before you use it. Eg: Dim sum As Integer (or) sum=10;  Enhanced Functionality Most of the languages provide powerful string manipulation based on the use of regular expression(A regular expression is a string of characters that define the pattern or patterns you are viewing. ). Some languages support easy access to API or Object model exported by application. 6/13/2016 8Introduction to scripts and scripting
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  CHARACTERISTICS OF SCRIPTINGLANGUAGE  Efficiency is not an issue Ease of use is achieved at the expense of efficiency eg: interpretation rather than compiling Focus is not on high performance but on the speed of development together with ability to make changes to meet new requirement. 6/13/2016 9Introduction to scripts and scripting