The Shell (csh, tcsh, sh, ksh)

Each time you type a command, a program called a ``shell'' accepts and interprets what you have typed, and sends your command on to be performed by the operating system. There are four shells available on the Suns and Convexes: the ``C'' shell (csh), the ``TC'' shell (tcsh), the ``Bourne'' shell (sh, the original UNIX shell) and the ``Korn'' shell (ksh). The TC-shell is like the C-shell (so called because its syntax is similar to the ``C'' language) but has a number of enhancements such as command line recall and editing, while the Korn shell is basically an enhanced Bourne shell (both these names refer to the authors). The C-shells (referring to both the original and the TC-shell) are in general easier to work with than the Bourne/Korn shells and you will most likely use one of them, at least initially. The C-shells have a few commands not available in the Bourne shell. Good examples are the alias command and the history command. Many people who enjoy using UNIX find they prefer one of the other shells; you can make your own choice and ask the system manager to make it your login default. If in doubt, try ``TCSH''.

When you begin, the C- and TC- shell executes your ``.cshrc'' file and then your ``.login'' file. Your ``.cshrc'' file contains setups for general use and the ``.login'' file is often used to set up the terminal. The Bourne and Korn shells execute only your ``.profile'' file. The plain C-shell is set up as your default shell as it is available on most UNIX system, but you probably prefer TCSH because it allows such convenient things as command line recall and editing using the arrow keys, just like in VMS. In addition the TC-shell has a feature, which will allow you to type just enough of a commandname, filename, or directory name to be unique; then press TAB and the shell will complete the name of the file for you (name completion). The Korn shell, while being the shell on which AT&T is standardizing, is not yet available from most vendors. The versions on our systems were obtained from third-party software companies. Be aware that the TC-shell is not a vendor-provided shell; The Korn shell is now part of the Solaris operating system.

All the shells have a few characters with special meaning, which will cause the shell to change the way it treats the command or the name you are typing. These include: $ & ! ; ( ) and others. Check the man page for your shell to find out more information on these ``metacharacters''. You can create a file for execution which contains only commands acceptable to your shell; this is called a ``shell script'' and is analogous to a DCL command file on VMS. It can be used to do the same kinds of things. More information is available in the ``SUNOS User's Guide: Doing More'' manual.

To avoid confusion, in most of the examples below we will only show the (T)C-shell version. If your account was created when this document was already available, you will have been given a ``.cshrc'' and a ``.login'' which will have examples of many of these already set up; or you can copy the one in /etc/local.cshrc or .login. For more information on KSH you should either read the man page on ksh, or contact a ksh guru.