1.4. Getting the 1993 Korn Shell
This book covers the 1993 version of the Korn shell. A large amount of
what's covered is unique to that shell; a subset of what is unique applies
only to the recent versions available directly from AT&T. In order
to make best use of the book, you should be using the 1993 Korn shell.
Use the following sequence of instructions to determine what shell you
currently have and whether the 1993 Korn shell exists on your system, and
to make the 1993 Korn shell be your login shell.
Determine which shell you are using.
The SHELL variable denotes your login shell.
Log in to your system and type echo $SHELL at the prompt.
You will see a response
containing sh,
csh, or ksh;
these denote the Bourne, C, and Korn shells, respectively.
(There's also a good chance that you're using a third-party
shell such as bash or tcsh.)
If the response is ksh, go to step 3.
Otherwise, continue to step 2.
See if some version of ksh exists on your system
in a standard directory.
Type ksh.
If that works (prints a $ prompt),
you have a version of the Korn shell; proceed to step 3.
Otherwise, proceed to step 5.
Check the version. Type echo ${.sh.version}.
If that prints a version, you're all set; skip the rest of these instructions.
Otherwise, continue to step 4.
You don't have the 1993 version of the Korn shell. To find out
what version you do have,
type the command
set -o emacs, then press CTRL-V.
This will tell you if you have the 1988 version or the Public Domain Korn shell.
In either case, continue to step 5.
Type the command /usr/dt/bin/dtksh.
If this gives you a $ prompt, you have the
Desktop Korn Shell, which is based on an early version of ksh93.
You may use this version; almost everything in this book will work.
Go to step 7.
You need to download an executable version of ksh93
or download the source and build an executable from it. These tasks are described in
Appendix C.
It would be best to enlist the help of your system administrator for
this step.
Once you have a working ksh93, continue to step 7.
Install ksh93 as your login shell. There are two
situations; pick the one appropriate to you:
- Single-user system
-
On a single-user system, where you are the administrator,
you will probably need to add the full path to ksh93 to
the file /etc/shells as the first step.
Then, you should be able to
change your login shell by typing
chsh ksh-name,
where ksh-name is the full path to the ksh93
executable.
If this works,
you'll be prompted for your password. Type in your password,
then log out and log back in again to start using the Korn
shell.
If chsh doesn't exist or doesn't work, check the
man page for passwd(1). Look for either the
-e or -s options
for updating your password file information.
Use whatever is appropriate for your system to change your login shell.
If none of the above works, you can
resort to editing the /etc/passwd file while
logged in as root.
If you have the vipw(8) command, you should use
that to edit your password file.
Otherwise, edit the file manually with your favorite text editor.
- Large multi-user system
-
This situation is even more complex than the single-user case.
It is best to let your system administrator
handle changing the shell for you. Most large installations have a "helpdesk"
(accessible via email or phone, or both) for entering such requests.
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