ch12-Python - Python Fundamentals and Scripting Languages 1...

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1 Python Fundamentals and Scripting Languages
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2 References http://www.linuxjournal.com/article/3882 “Why Python?” by Eric Raymond in the Linux Journal , May 1st 2000. http://www.tcl.tk/doc/scripting.html “Scripting: Higher Level Programming for the 21st Century”, John K. Ousterhout, IEEE Computer , March 1998. http://www.geeksaresexy.net/2008/07/25/the-ascent-of-scripting-la “The ascent of scripting languages” by Chip. July 25, 2008. From the site Geeks are Sexy ™ Python web page: http://www.python.org/
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3 What is a Scripting Language? Wikipedia: A scripting language , script language or extension language , is a programming language that controls a software application. "Scripts" are often treated as distinct from “programs", which execute independently from any other application.
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4 Early Scripting Languages Controlled the actions of system programs Job Control Language (JCL):controlled batch job executions on IBM mainframes Shell scripts: A series of instructions to the shell, or command line interpreter, of a UNIX system When used like this, scripting languages take pre-existing components, maybe in different languages, and combine them so they work together.
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5 IBM JCL – 3 Basic Commands JOB statement, which identifies the start of the job, and information about the whole job, such as billing, run priority, and time & space limits. EXEC statement, which identifies the program to be executed in this step of the job, and information about the step. DD (Data Description) statements, which identify a data file to be used in a step, and detailed info about that file. DD statements can be in any order within the step. http://en.wikipedia.org/wiki/Job_Control_Language , 3/22/2010
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6 Example Shell Script from Ousterhout select | grep scripting | wc where select is a program to read and output the text that is currently selected on the display grep is a program reads input and outputs the lines containing "scripting"; wc is a program to count the lines in its input. “|” is the pipe command that directs the output from one program to the input of the next program.
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7 Modern Scripting Languages Perl, Python, Ruby, … More like a traditional programming language than early scripting languages. Higher level in the sense that programmers don’t have to worry about many of the details that are a part of C-like languages No explicit memory allocation/deallocation, for example
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8 Modern Scripting Languages It’s possible to write full-featured programs in these languages Used frequently today for “quick-and-dirty” programming – Quick results Small programs; e.g., system utilities Python advocates claim it is more scalable than Perl and other scripting languages – easy to write large programs.
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9 What is a Scripting Language? another definition
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ch12-Python - Python Fundamentals and Scripting Languages 1...

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