Unix Lab

Glossary of Terms

Definitions of various terms are shown here. These terms are in alphabetical order. Click on the colored text to go to that part of the lab dealing with that term.

The Unix C shell allows you to customize your interface to Unix by providing aliases or alternate names for commands. These are placed in your .cshrc file in your home directory. Click for more information.

class files
Class files are files containing bytecodes which are pseudo machine instructions produced by a Java compiler from a file containing source code. These files are interpreted by a Java Virtual Machine to execute the instructions corresponding to the bytecodes. Click for more information.

full path names
File names in Unix can be local (the name you can use if you are in the directory in which they live), or their full path name that identifies the string of directories from the root to the named file. Click for more information.

The C Shell in Unix has the capability to recall previously-issued commands. These previous commands are maintained in a history file which is accessible to the Shell and can be re-issued by the user. Click for more information.

IDE (Integrated Development Environment)
Modern program development environments provide programs that allow the programmer to edit source code, compile it, and even execute it within the control of these programs called IDEs. Click for more information.

IP address
Every computer attached to the internet has a unique identifying address consisting of a sequence of numbers. This address is called its IP address. Click for more information.

The jar utility is used to package together into one file multiple Java class files in a form that allows them to be accessed by the Java compiler and the Virtual Machine. In addition, the contents of jar files (files previously generated by the jar utility) can be reconstructed if needed later. Click for more information.

The kernel is the "core" of the Unix operating system. For example, it is responsible for interacting with the computer at the hardware level. Click for more information.

Metacharacters are characters that have special meaning in certain contexts. For example, the characters '*' and '?' have certain special significance in building regular expressions or in the identification of groups of files to the Shell.

Multitasking is a characteristic of Unix operating systems. A multitasking operating system can have several processes running concurrently. Click for more information.

A pipe is a mechanism in Unix that allows several programs to be running concurrently with the output from one being passed to the next as input. Click for more information.

A Unix process is a task that has its own identity as an executable program. A process may be a user-written program or a Unix utility, for example. Click for more information.

In Unix the standard input file is associated with the keyboard and the standard output file is associated with the terminal. The user can re-direct these associations by naming alternate files in the command line. Click for more information.

regular expressions
A regular expression is a string of characters used by certain Unix utilities and the Unix shell to specify matching rules. These matching rules are used for such things as specifying file names or locating strings in text files. Click for more information.

scp is a utility which allows you to copy files from one computer to another. The key feature is that all communication between computers is encrypted. Click for more information.

The shell is the layer of software that acts as intermediary between the user and the kernel of the Unix operating system. Click for more information.

ssh is a utility which serves the same purpose as telnet except that all communication between computers is encrypted. Click for more information.

standard files
In a Unix environment, certain files are taken as the default locations for input or output. The standard input file is where input is expected, the standard output file is where output will be placed. The standard input file is usually associated with the keyboard and the standard output file is usually associated with the terminal but the user can alter these associations. Click for more information.

The tar utility is a tool for packaging into one file the contents of one or more files and even directories. Such a tar file can later be used to re-construct the files and directories contained within it preserving the hierarchical structure. Click here for more information.

telnet is a utility which allows users on one machine to login to other machines on the network provided they have accounts on those machines. Click for more information.

Unix is a multitasking, multi-user operating system. It is used on a wide variety of computers from mainframe supercomputers to workstations to PCs. Click for more information.

Unix file names
Unix allows you considerable freedom in the names you choose for files. All Unix systems will allow you to use 14 characters in the filename but most will allow names much longer. Although Unix will allow almost any characters in the file name, you will avoid problems if you restrict yourself to:

These pages were developed by John Avila SJSU CS Dept.