Shell Features. Chapter 14. Overview. Bourne Shell ($) – Original shell for UNIX environment developed for AT&T V.2. Does not support alias, history or command line editing and is used primarily by system admins.
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The r (repeat) command is one of many predefined aliases in the Korn shell. This command is similar to the F3 key in DOS.
The simplest way to repeat commands in the Bash shell is to press the up arrow, or Ctrl+P keys, and down arrow, or Ctrl+N keys. The Bash shell offers additional features for repeating previous command lines not available in the Korn shell
!! -Executes the previous command
!* -repeats all arguments from the previous command
!$ -repeats the last argument from the previous command
!number – executes command number from the history list
!n:p - views command n from the history list without executing it
Both the Korn and Bash shells contain another feature that completes the name of a file or command by turning on the command line editor.
To use the completion feature:
Type a command, such as ls, cat, rm and so on, followed by one or more characters of a file name.
Press the Esc and backslash keys (Esc \) in sequential order, for the Korn shell, or the Tab key, for the Bash shell.
Another way to use the completion feature is to request the shell to display a list of files that matches the entered filename. To display this list the student uses Esc= for the Korn shell or Tab Tab, entered twice, in the Bash shell.
If a Korn shell user wants to customize the environment, that user needs to create or modify the .profile file and then the user must export the ENV variable, as shown here:
ENV =$HOME/.kshrc;export ENV
Korn shell specific commands and features should be placed in the .kshrc file. The .kshrc file automatically is read each time a new shell, such as a new Terminal window, or subshell is started, so there is nothing to export.
The contents of the .kshrc file typically include the following:
A customized prompt
The .profile file is read only once, while the .kshrc file is read every time a new Korn shell is started. To have the system reread the .kshrc or .profile files after changes have been made the user either can log out and log back in or can type the following from the command line:
$. (dot) ~/.kshrc (or $. .kshrc from the home directory)
$. (dot) ~/.profile (or $. .profile from the home directory)