Intro to UNIX Shells

A UNIX Shell is in simplest terms, a command line interpreter, that takes the users input and gives it to the Kernel. If you are familiar with DOS, you will remember the 'command.com' that file takes the users information and passes it to the operating system in a way it can be understood by the system. With DOS you only had one type of shell, but with UNIX you have a variety, each with their own abilities, pluses and minuses.

Keep in mind as you read about these shells, that though they may have major differences when they were created, that they have been updated and many features that were once only available in a single shell, may be available in other shells. This is more of a history lesson.

'sh'
The Bourne shell, named after its creator Steve Bourne is the oldest shell for most major distributions of UNIX and LINUX. Most shells today are in some fashion derived from the Bourne shell.

'csh'
The C Shell. The C shell is a great shell that has many advantages over the original Bourne shell, it was the first to introduce a history (the ability to scroll up, to view past commands). Also the C Shell as the name implies also integrates a great portion of the C programming language. If you are able to program in C, you can pretty much do it all in a shell script or from the command line, if you so desired.

'ksh'
The Korn Shell. Named after its creator David Korn. This shell is able to do most of the things both the Bourne, and C Shell can do, and improves on them. For instance, the history feature is available, plus you are able to call up the history, edit the command, and then re-run it.

'bash'
The Bourne-Again Shell. This is probably the most widely used shell to date, and is the default shell for most newer Linux distributions. Again it integrates most of the above features and improves upon them. It was developed by the Free Software Foundation.

There are many other shells out there, but chances are if you are using a UNIX style operating system, you are using one of the above mentioned shells. My personal favourite is the bash shell, which also happens to be the first one I was exposed towards, so I may be biased. However typically when shell scripting, I use the korn shell because of its programming friendly structure.

How do you know what UNIX shell I am using?

Type "ps" and then hit return at your shell prompt and you should get something similar to:

$ ps
PID TTY TIME CMD
13087 pts/1 00:00:00 bash
13121 pts/1 00:00:00 ps

The numbers under PID, TTY, TIME etc should all be different from machine to machine, and the number of lines of programs running may also. But one line you have will be probably "bash" "csh" "sh" "ksh".

Another way to check is to type the following:

grep your-user-name /etc/passwd (eg grep ken /etc/passwd)

Which will return you something along the lines of:

ken:x:501:501:Ken:/home/ken:/bin/bash

The last portion of that line is '/bin/bash' which tells you your default shell when you login.

Ken Dennis
Ken.Dennis@Gmail.com
http://KenDennis-RSS.homeip.net/

---

Microsoft Great Plains Partner Selection: Overview

Microsoft Great Plains, Navision, Solomon and Axapta are Microsoft Business... Read More

C++ Tutorial 2, Input and Variables

This is the tutorial where we really get into programming.... Read More

Microsoft CRM Customization - Processing In/Out-Going Email Messages

We would like to give you several situations, when you... Read More

Microsoft CRM USA Nationwide Remote Support

Remember old good days when your company probably had Great... Read More

Builders Beware

Which Type of Shop Can Rely On A Home Built... Read More

Imagine if Everyone Working In Your Office Was In Synch?

Microsoft-Outlook is a pretty amazing program. So much more than... Read More

Chinese Input - Step by Step Instruction on How to Input Chinese Characters in English Windows XP

Enabling Chinese input is quick and easy, there are only... Read More

Software Process Improvement -A Successful Journey

Background: For many organizations like ours, the interim target of... Read More

Great Plains Bill of Materials Setup & Customization for Process Manufacturing ? Overview

Microsoft Great Plains has full-featured Manufacturing suite of modules: Capacity... Read More

Microsoft Great Plains Upgrade ? Things to Consider and FAQ

If you have Microsoft Great Plains and support it for... Read More

Corel WordPerfect 7 Macro Programming Example

Case study: A secretary using Corel WordPerfect 7 is often... Read More

Microsoft Great Plains in Metal Distribution: Implementation & Customization ? Consultant Overview

Microsoft Business Solutions Great Plains serves to the wide spectrum... Read More

Importance of Coding Standards

Programming Help for BeginnersWe write programs to instruct computers. When... Read More

Healthcare Preventive Maintenance Software

Healthcare facilities such as clinics, hospitals, and biomedical laboratories can... Read More

EDI: Electronic Document Interchange for Microsoft Great Plains ? Overview for Software Developer/Pr

Microsoft Great Plains - Microsoft Business Solutions accounting and ERP... Read More

Implementing Microsoft CRM: setup and configuration ? notes for IT specialist

Microsoft Business Solutions CRM is web-based CRM application, deploying all... Read More

Can You Calculate Complex Financial Calculations?

Are you a whiz at calculating financial information? Not the... Read More

Running a Program on a Remote Server Using SSH

How do you run a program on a remote server... Read More

Lotus Domino/Notes - Microsoft Great Plains Tandem as ERP with Documents Workflow - Overview for IT

Lotus Domino/Notes ? Microsoft Great Plains tandem as ERP with... Read More

Destination: Desktop for Google

First we had the original Google search that evolved into... Read More

40/sec to 500/sec

IntroductionSurprised, by the title? well, this is a tour of... Read More

Microsoft Great Plains - Microsoft RMS Integration ? overview

Microsoft Great Plains and Microsoft Retail Management System (Microsoft RMS)... Read More

Linux Vs. Windows

This article will not attempt to advocate the use of... Read More

Put Some Pizazz in Your Software Arsenal

The software giants don't do everything and don't always produce... Read More

Microsoft CRM for Corporate Business ? Working Offline

If your company has regional and worldwide operations, you might... Read More

10 Steps To Secure And Manage Your Passwords

Passwords protect your most sensitive personal, financial and business information.... Read More

These Items Are A Must Before Making The Decision To Purchase Any Off-The-Shelf Software

1. What determines the software price? Is it Per Seat... Read More

Microsoft Great Plains as ERP and Microsoft CRM as CRM

If you have Microsoft Great Plains and support it for... Read More

Groupware: Answers the 5 Questions of Document Collaboration

Every organization which creates collaborative documents, whether they are budgets,... Read More

Great Plains Dexterity Development: FAQ

Microsoft Business Solutions Great Plains is Dexterity-written application and currently... Read More

Need of Document Management System (DMS)

Document Management or Enterprise Information Management is perhaps one of... Read More

Microsoft Great Plains Implementation ? Overview for IT Director/Controller

What is installation in the language of technology? Installation... Read More

Software: What Suits Me?

Almost all new and major brand of PCs come with... Read More