Simple Shell

Shell is a UNIX term for the interactive user interface with an operating system. The shell is the layer of programming that understands and executes the commands a user enters. In some systems, the shell is called a command interpreter.

A Simple Shell Program In C Programming Language

The simple shell is ALX project,it helps student to understand the advanced concepts behind the shell program include process, system call, bit manipulation, file managment, error handling ...

Genreral

• Who designed and implemented the original Unix operating system
• Who wrote the first version of the UNIX shell
• Who invented the B programming language (the direct predecessor to the C programming language)
• Who is Ken Thompson
• How does a shell work
• What is a pid and a ppid
• How to manipulate the environment of the current process
• What is the difference between a function and a system call
• How to create processes
• What are the three prototypes of main
• How does the shell use the PATH to find the programs
• How to execute another program with the execve system call
• How to suspend the execution of a process until one of its children terminates
• What is EOF / “end-of-file”?

Getting SSH

In order to install the shell and get benefits of it's features you need to clone the current project, and compile it. You need to make sure that this shell tested and garantees work based on gcc-4.8 and the C90 standard.

Features

• Display a prompt and wait for the user to type a command. A command line always ends with a new line.
• If an executable cannot be found, print an error message and display the prompt again.
• Handle errors.
• Hndling the “end of file” condition (Ctrl+D)
• Hanling the command line with arguments
• Handle the PATH
• Support the exit features and the exit status
• Handle the Ctrl-C to not terminate the shell
• Handling the command seperator ;
• Handling && and || logical operators
• Handle variable replacements $? and $$
• Handle the comments #
• Support the history feature
• Support the file input

Builtins

• The exit builtin exit [STATUS]
• The change directory cd [DIRECTORY] | [OPTION]
• Display the environnment variables env
• Initialize a new environnment variables or created if not match setenv [VARIABLE] [VALUE]
• Remove an environnment variable unsetenv [VARIABLE]
• Support the aliases alias [name [='value'] ...]
• Display help help [BUILTIN]
• Display history history

Authors

Emmanuel Ebuka Ejie - ALX Software Engineer Student

Franklin Chidera - ALX Software Engineer Student