Glossary of Unix programming

interactive mode
In interactive mode, the shell reads input from you and executes the commands that you specify. This mode is called interactive because the shell is interacting with a user.

invisible or hidden file
A file whose name starts with the . character. By default the ls command does not list these files. You can list them by specifying the -a option to ls.

iteration
A single execution of the body of a loop.

kernel
The heart of the UNIX system. It provides utilities with a means of accessing a machine’s hardware. It also handles the scheduling and execution of commands.

Korn shell
A user interface for UNIX with extensive scripting (programming) support. Written by David G. Korn. The shell features command-line editing and will also accept scripts written for the Bourne shell.

library
A file that contains only functions. Usually libraries contain no main code.

literal character
A character with no special meaning and which causes no extra action to be taken. Quoting causes the shell to treat a wildcard as a literal character.