Unit 1-introduction to scripts
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Scripting languages are used to automate tasks and extend software functionality. They are interpreted rather than compiled, allowing tasks to be automated by writing scripts that call external programs. Popular scripting languages include Perl, PHP, Python, and TCL. Scripting is faster than traditional programming because scripts can be developed quickly to control applications and build interfaces without concern for runtime efficiency. Scripting originated with shell scripts in UNIX and is now commonly used for web development through CGI and client-side scripting.
Unit 1-introduction to scripts
- 1. BY SANA MATEEN 6/13/2016 1Introduction to scripts and scripting
- 2. INTRODUCTION TO SCRIPTS AND 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
- 3. 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
- 4. 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
- 5. 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
- 6. SCRIPTING TODAY Scripting allows 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
- 7. CGI SCRIPT ISAPI TECHNOLOGY 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
- 8. CHARACTERISTICS OF SCRIPTING LANGUAGE 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
- 9. CHARACTERISTICS OF SCRIPTING LANGUAGE 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