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Advanced Unix Concepts - Glossary

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UNIX is an operating system originally developed in the 1960s and 1970s by a group of AT&T Bell Labs employees including Ken Thompson and Dennis Ritchie. UNIX was designed to be portable, multi-tasking and multi-user in a time-sharing configuration. With the client/server framework splitting the computing environment into two (often, three) distinct parts, UNIX today is firmly entrenched as the operating system of choice for the server community. Enterprise databases run on UNIX, and Oracle runs with full vigor on UNIX systems. Moreover, Internet Service Providers (ISP) use UNIX machines and UNIX remains the preferred platform for Web servers and electronic commerce.
absolute path name
An absolute path name is the address of a file or directory, specified with the root directory as the starting point.
access mode
The access mode is the first column of an ls -l listing. The access mode is composed of a file type followed by the user permissions, group permissions, and other permissions.
access string
An access string is the symbolic argument used with the chmod command.
account
Your account (or user account) is a unique environment within a UNIX system. An account comes with a user ID and a home directory.
alias
An alias is a brief label that provides a command shortcut. For example, by defining an alias, you can execute a complex command by typing only a few characters of the alias.
anchor
An anchor is a metacharacter such as ^ or $ that restricts a match to a particular position.
Anonymous FTP
Anonymous FTP is a connection to a public FTP site without the use of an assigned user name and password. You enter the user name anonymous to sign on and your access is limited.
append redirection operator
Using the append redirection operator, >>, you can add output to the end of an existing file.
archive
An archive is a set of files that are packaged as a single, large file.
arguments
Command arguments are the files, directories, or other objects that a command acts on.
block
A block is a unit of storage equal to 512 bytes.
buffer
A buffer is an area of memory where data are temporarily stored.
case sensitive
When a text search is case sensitive, the search treats uppercase and lowercase letters differently. If uppercase and lowercase letters are treated the same way, then the search is considered to be case in-sensitive.
command history
Command history is a C shell feature that lets you display previously entered commands, rerun them, or run modified versions of them.
command interpreter
Command interpreter is another term for the UNIX shell, because it processes the commands you enter.
command mode
Command mode is one of two modes of operation in vi. In command mode, you can move the cursor and issue editing commands, but you must switch to text mode to add text.
command-line interface
A command-line interface is one way of interacting with UNIX, in which you type commands at a prompt and the shell interprets them.
configuration options
Configuration options control vi's behavior. Use the :set command to manage these options.
Ctrl-C


Pressing Ctrl-C interrupts a command and returns you to the shell prompt. Ctrl-C is executed by holding down the Control key (labeled Ctrl) and pressing the C key.
current directory
Your current location in the file system. By default, UNIX commands apply to the current directory.
cwd variable
The cwd variable is a C shell variable that stores the name of your current working directory.
default printer
When you don't specify a printer name with your print command, the print request is sent to your default printer. The system administrator defines your default printer for you.
directory
A directory contains files and other directories. A directory is like a folder on Macintosh or Windows.
directory tree
A directory tree is the set of all files and subdirectories organized under a particular directory.
disk usage
Disk usage is the amount of storage space your files occupy on the disk.
download
To download means to transfer data from a remote computer.
ex editor
ex is a line editor that serves as an underlying program for the vi editor. A line editor is a program in which you see only one line at a time.
extract
To extract files from an archive means to copy them out of an archive and onto the filesystem.
file
A file is the basic unit of storage on UNIX, just as on any operating system.
file compression
File compression is a way of packing a file's contents more efficiently, so that the file takes up less disk space.
file owner
The file owner is typically the user who created the file. You can change permissions only on files you own.
File Transfer Protocol
The File Transfer Protocol, or FTP, is the set of communication rules that computers use to exchange files.
file type
The file type is the first character in an access mode. The most common file types are - for a regular file and d for a directory.
filter
A filter can take input from another command, manipulate the data in some way, and produce output. Filters are regular UNIX commands. Examples include head, tail, more, pr, grep, and sort.
FTP
Abbreviation for File Transfer Protocol.
FTP session
When your computer connects to an FTP server, also called an FTP site, you are engaged in an FTP session.
group
A group allows an arbitrary set of users to share files. When a user is a member of the file's group, the user will have that file's group permissions.
group permissions
Group permissions are the second set of read/write/execute permissions in an access mode. Group permissions apply to users that are members of the file's group.
GUI
A GUI, short for graphical user interface, is a system of windows, menus, and icons that you can click and drag with a mouse. Operating systems such as Macintosh, Windows, and UNIX provide a GUI.
Hard link
A hard link is another name for a file.