Whatever operating system you choose, a shell will be an important part of it. A shell is usually defined as software that provides the end user with an interface. In technical terms, the shell is the part of the software that gives you access to the kernel. The term shell is used freely and can mean many things to many people, especially in the computing field. For the most part, however, a shell is regarded as any software that surrounds or is built around any specific component, whether it be an operating system, web browser, email system, etc.
When referring to an operating system’s shell, there are two main types. One is the graphical user interface and the other is the command line. Computers running Window’s operating systems use GUI shells, whereas DOS and many Unix shells use the command line to gain access to the services of the kernel.
As stated above, shells are mostly used to gain access to the services of the kernel. For the most part, this includes launching or loading programs and accessing files and directories. Several popular UNIX-based shells include csh, tcsh, sh (these are all categorized as Bourne shells) ksh (Korn shell) and the GNU version shell called bash.
Since each UNIX-based shell can include specific commands and protocols, it is important to confirm which shell is on a specific computer. Figuring out which shell you are using is extremely easy and only takes a few seconds.
For UNIX-based shells, the version can easily be reported to you by using the echo $0 command:
unix% echo $0
Once the command has been entered, you should receive confirmation of the type of shell you are running, for instance:
tcsh, csh, sh, ksh or bash