Operating Systems

This repository contains the assignments for the Academic Courses "Operating Systems" taught in the Fall of 2018-2019 in Aristotle University of Thessaloniki - Electrical and Computer Engineering.

The purpose of this project is the better understanding of Linux shell via the implementation of a command line interpreter or shell interpreter and a Makefile in C programming language.

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Functionality

The shell that was requested should be able to understand Linux commands with or without arguments. Thus, is reasonable to create a parsing process for user's input stream. The functionality of our shell exceeds Linux command Line, because of the operators "&&" and ";". Using "&&" operator between two commands, the second command will be executed only if the first one is successfully executed. On the other hand, using ";" operator between two commands, the second command will be executed independently of the execution of the first one.

Moreover the shell is able to:

• Redirect input via '<' character.
• Redirect output via '>' character.
• Create pipelines via '|' character.

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Modes

The shell should be able to work in two modes, Interactive and Batch.

• Interactive: shell is executed with no arguments

./myshell

• Batch: shell is executed with a file (of commands) as argument

./myshell batchfile

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Execution

A Makefile is used to execute our code. To compile the source code we can use:

make all

while to run it:

./bin/myshell

If a batchfile of commands should be used, we write instead:

./bin/myshell batchfile