The Functions Of A Command Line Interpreter Computer Science Essay

A system plan that accepts user bids and converts them into the machine bids required by the operating system or some other control plan or application. COMMAND.COM was the bid processor that accompanied DOS and Windows 95/98. Subsequent Windows versions replaced COMMAND.COM with CMD.EXE. In Unix/Linux, bid processors are called “ shells ” A

The chief thoughts of CLIP are to back up translator based instruction and to give pupils better and clearererror messages in their native linguistic communication.

In additionto these, it should be possible to incorporate a visual image faculty with the translator. This requirementhas its roots in our visual image tool VIP ( Virtanenet al. 2005 ) , since we are non willing to keep two separate translators

Default handiness dramatically changed function of Perl in Unix system scripting and everyday text processing. For most decision makers it is much easier to utilize Perl that any of the older options. The chief consideration here is the power of the linguistic communication and handiness of a really good, built-inA debugger.

A Neither knock nor AWK has built-in debugger installed by default. And that entirely tips the graduated tables in Perl favour, as each decision maker has a batch of things to make to pass clip thinking where he made error utilizing multipleA A echo/printA statements.A

That ‘s why Perl is bit by bit displacing older Unix public-service corporations such asA cut, A sed, A A wc, and, of class, A AWK.A Often you can replace rather complex set of pipe phases that use authoritative UNIX public-service corporations with one Perl cringle.

Do n’t construe me incorrect, pipes are a approval and highly powerful tool that each UNIX admins should utilize to the soap, but if you can avoid unneeded complexness, why stick to old patterns.

Applications

Perl has many and varied applications, compounded by the handiness of many criterion and third-party faculties.

. Perl is known as one of “ the three Ps ” ( along withPythonA andA PHP ) , the most popular dynamic linguistic communications for composing Web applications. It is besides an built-in constituent of the popularA LAMPsolution stackA for web development. Large undertakings written in Perl includeA cPanel, A Slash, A Bugzilla, A RT, A TWiki, andA Movable Type. Many high-traffic web sites use Perl extensively. Examples includeA Amazon.com, A bbc.co.uk, A Priceline.com, A Craigslist, A IMDb, [ 37 ] A LiveJournal, A SlashdotandA Ticketmaster.

Perl is frequently used as aA glue linguistic communication, binding together systems and interfaces that were non specifically designed to interoperate, and for “ informations munging ” , A that is, change overing or treating big sums of informations for undertakings such as making studies. In fact, these strengths are closely linked. The combination makes Perl a popular general-purpose linguistic communication forA system decision makers, peculiarly because short plans can be entered and run on a individual bid line.

Perl is besides widely used in finance and inA bioinformatics, where it is valued for rapid application development and deployment and for its capableness to manage big data-se

Execution

Perl is implemented as a nucleus translator, written in C, together with a big aggregation of faculties, written in Perl and C. The beginning distribution is, as of 2009, 13.5A MBA when packaged in aA pitch fileA andA compressed.A The translator is 150,000 lines of C codification and compiles to a 1A MB feasible on typical machine architectures. Alternatively, the translator can be compiled to a nexus library and embedded in other plans. There are about 500 faculties in the distribution, consisting 200,000 lines of Perl and an extra 350,000 lines of C codification. ( Much of the C codification in the faculties consists of character-encoding tabular arraies. )

The translator has an object-oriented architecture. All of the elements of the Perl language-scalars, arrays, hashes, coderefs, filehandles-are represented in the translator by C structs. Operationss on these structs are defined by a big aggregation of macros, typedefs, and maps ; these constitute the Perl C API. The Perl API can be perplexing to the naive, but its entry points follow a consistent naming-scheme, which provides counsel to those who use it.

The life of a Perl translator divides loosely into a compile stage and a tally stage. [ 40 ] A In Perl, theA phasesA are the major phases in the translator ‘s life-cycle. Each translator goes through each stage merely one time, and the stages follow in a fixed sequence.

( two ) Python: Python is an taken, synergistic, object-oriented scheduling linguistic communication. It is frequently compared to Tcl, Perl, Scheme or Java.

Python combines singular power with really clear sentence structure. It has faculties, categories, exclusions, really high degree dynamic informations types, and dynamic typewriting. There are interfaces to many system calls and libraries, every bit good as to assorted windowing systems ( X11, Motif, Tk, Mac, MFC ) . New constitutional faculties are easy written in C or C++ . Python is besides useable as an extension linguistic communication for applications that need a programmable interface.

The Python execution is portable: it runs on many trade names of UNIX, on Windows, DOS, OS/2, Mac, Amiga… If your front-runner system is n’t listed here, it may still be supported, if there ‘s a C compiler for it. Ask around on comp.lang.python — or merely seek roll uping Python yourself.

The Python execution is copyrighted but freely useable and distributable, even for commercial usage.

The Python translator is normally installed asA /usr/local/bin/pythonA on those machines where it is available ; puttingA /usr/local/binA in your Unix shell ‘s search way makes it possible to get down it by typing the bid

python

to the shell. Since the pick of the directory where the translator lives is an installing option, other topographic points are possible ; look into with your local Python guru or system decision maker. ( E.g. , A /usr/local/pythonA is a popular alternate location. )

On Windows machines, the Python installing is normally placed inA C: Python27, though you can alter this when you ‘re running the installer. To add this directory to your way, you can type the undermentioned bid into the bid prompt in a DOS box:

set path= % way % ; C: python27

Functions

Functions and methods within Python are created through the def bid. These are highly utile when you might otherwise reiterate the same piece of codification. A typical simple map might look therefore:

def square ( ten ) :

return x*x # note, one can besides utilize x**2 for ten squared,

# x**3 for ten cubed, x**4 for x^4 and so on…

This map takes one input ( x ) and returns x^2 to whatever called it. So if your codification contains the above map, you might entree it in the undermentioned ways:

print square ( 9 ) # prints 81 ( 9*9 )

a=5

print square ( a ) # prints 25 ( 5*5 )

b=square ( 3 ) # assigns the value 9 to b ( 3*3 )

c=square ( B ) # assigns the value 81 to c ( b*b )

Functions can be called from within maps:

def to_the_power_of_four ( ten ) :

return square ( x ) * square ( x ) # gets x^2^2 ( i.e. x^4 )

A note about remarks: A If a hash ( # ) mark is used in the codification organic structure ( i.e. non portion of a print statement ) so whatever follows it is a remark. A remark is ignored by the Python translator and it is considered good practise to utilize them to do the codification more clear by a human – particularly utile when one creates larger pieces of codification.

A map does non needfully necessitate to return a value, nor does it necessitate to have a value. Look at these two maps:

def say_hello ( name ) :

print “ Hello ” , name

def give_me_a_number ( ) :

return 1234

( three ) Apparition

Phantom is a powerful Windows mechanization scripting linguistic communication. The Phantom translator runs standard ASCII Phantom books ( syntax similar to C ) to interact with Windows common controls. Virtually any figure of common or insistent undertakings can be automated. It is besides a utile tool for machine-controlled testing. The Phantom linguistic communication has many characteristics, including constitutional maps, the ability to add maps and user-defined DLLs, flow control, and book mistake and log end product. In order to utilize the mechanization characteristics, you will hold to larn the scripting linguistic communication foremost in order to make your usage books. The download comes with everything including some sample books and full certification.

Phantom is a powerful scripting linguistic communication used toautomate Graphical User Interfaces ( GUIs )

aˆ? Used for

– Trial Automation

– Procedure Automation

– Application Performance Analysis

aˆ? Three merchandises are provided that support the Apparition

linguistic communication

– Apparition Test Driver ( PTD )

– Apparition Sidekick

– Apparition Command Line Utility

aˆ? Phantom can be customized to back up client demands

Features

aˆ? Large built-in GUI mechanization

map set

aˆ? Exception handling

aˆ? Full book flow control

aˆ? Complex built-in informations types

– Windowss

– electronic image

– option sets

aˆ? User-defined maps

aˆ? Intuitive window entree

Hierarchy

Phantom Uses

aˆ? QA Test Automation

– Automate scripted manual trial processs

– Arrested development proving

– Functional testing

– Performance testing

aˆ? Process Automation

– Insistent manual undertakings

– Time devouring undertakings

– Procedure programming

aˆ? Application Performance Analysis

– Repetitive emphasis analysis

– Response clip analysis

– Load response analysis

Phantom is a powerful

A

( four ) The Java Interpreter

javaA interprets ( executes ) Java bytecodes.

Java [ options ] classname & lt ; args & gt ;

java_g [ options ] classname & lt ; args & gt ;

Description

TheA javaA bid executes JavaA classA files created by a Java compiler, for case, A javac.

TheA classnameA statement is the name of the category to be executed.A classnameA must be to the full qualified by including its bundle in the name, for illustration:

% Java java.lang.String

Note that any statements that appear afterA classnameA on the bid line are passed to theA mainA method of the category.

javaA expects the binary representation of the category to be in a file calledA classname.classA which is generated by roll uping the corresponding beginning file withA javac. All Java category files end with the file name extensionA .classA which the compiler automatically adds when the category is compiled.classnameA must incorporate aA mainA method defined as follows:

category Aclass {

public inactive nothingness chief ( Stringing argv [ ] ) {

. . .

}

}

javaA executes theA mainA method and so exits unlessA mainA creates one or more togss. If any togss are created byA mainA thenA javaA does n’t go out until the last thread issues.

When you define your ain categories you need to stipulate their location. Use CLASSPATH to make this. CLASSPATH consists of a colon detached list of directories that specifies the way. For illustration:

. : /home/xyz/classes

.

Option

-debug

Allows the Java debugger, A jdb, to attach itself to thisA javaA session. WhenA -debugA is specified on the bid lineA javaA displays a watchword which must be used when get downing the debugging session.

-cs, -checksource

When a compiled category is loaded, this option causes the alteration clip of the category bytecode file to be compared to that of the category beginning file. If the beginning has been modified more late, it is recompiled and the new category file is loaded.

-classpathA way

Specifies the pathA javaA uses to look up categories. Overrides the default or the CLASSPATH environment variable if it is set. Directories are separated by colons. Therefore the general format forA pathA is:

. : & lt ; your_path & gt ;

For illustration:

. : /home/xyz/classes: /usr/local/java/classes

-v, -verbose

CausesA javaA to publish a message to stdout each clip a category file is loaded.

-verify

Performs byte-code confirmation on the category file. Beware nevertheless, thatA Java -verifyA does non execute a full confirmation in all state of affairss. Any code way that is non really executed by the translator is non verified. Therefore, A Java -verifyA can non be relied upon to attest category files unless all codification waies in the category file are really run.

PHP Command Line Interpreter

PHP has steadily progressed to the phase that command line use of the PHP.exe is easier than of all time before ; particularly with the new PHP 5 betas. This is most fortunate because it makes proving out small scriptlets of PHP codification easier than of all time. And with the new OOP and XML capablenesss of PHP there are plentifulness of chances to prove PHP fast and easy with bid line trial books and even simple batch harnesses that rip through 10 fluctuations on a OOP definition subject. The side benefit? Users all of a sudden discover that with regular looks, great database connectivity, ever great file I/O oiperations, easy array use – in short the whole bequest Perl-like and enhanced characteristics, PHP makes a great OS scripting agent.

he simplest usage of PHP bid line manner is to run a phpfile straight:

A A php phptest.php

However before you do so it is worthwhile doing the undermentioned alterations to setups in to your running environ:

A A 1 ) put the booklet incorporating the php.exe on the way. For Windows users this is –

A A A A Path = degree Celsius: phpfolder ; % Path %

A A 2 ) do a transcript of the php.ini file and shop it in this directory/folder ;

A A 3 ) make the undermentioned alterations to the php.ini file:

A A A a-A output_buffering=off //in synergistic manner buffering stables end product until buffer fill

A A A b- implicit_flush=on // this warrants end product is immediate

A A A c- max_execution_time = 30000 //second of elapsed clip the plan can run

Decisions

Choice of the Ist scheduling linguistic communication for learning should be done. However, when confronting cruel world, this can non ever be the instance. In this phase it is difficult to state how successful CLIP will be. With the new talk stuff and integrating of a visual image faculty, we expect to acquire a

system in which the scholar merely uses the belongingss he or she knows, and in which the visual image will assist the pupils non merely to understand the plan behavior but besides to debug their codification.