glossary.html

linux-unix130.linux.and.unix.ebooks130 linux and unix ebookslinuxLearning Linux - Collection of 12 E

<DD>The process of starting the operating system (UNIX).
<DT><B><TT>Bourne shell</TT>
</B>
<DD>The original standard user interface to UNIX that supported limited programming capability.
<DT><B><TT>BSD</TT>
</B>
<DD>Berkeley Software Distribution.
<DT><B><TT>BSD UNIX</TT>
</B>
<DD>Version of UNIX developed by Berkeley Software Distribution and written at University of California, Berkeley.
<DT><B><TT>bug</TT>
</B>
<DD>An undocumented program feature.
<DT><B><TT>C</TT>
</B>
<DD>Programming language developed by Brian W. Kernighan and Dennis M. Ritchie. The C language is highly portable and available on many platforms including mainframes, PCs, and, of course, UNIX systems.
<DT><B><TT>C shell</TT>
</B>
<DD>A user interface for UNIX written by Bill Joy at Berkeley. It features C programming-like syntax.
<DT><B><TT>CAD</TT>
</B>
<DD>Computer-aided design.
<DT><B><TT>cast</TT>
</B>
<DD>Programming construct to force type conversion.
<DT><B><TT>cat</TT>
</B>
<DD>Concatenate files command.
<DT><B><TT>CD-ROM</TT>
</B>
<DD>Compact Disk-Read Only Memory. Computer-readable data stored on the same physical form as a musical CD. Large capacity, inexpensive, slower than a hard disk, and limited to reading. There are versions that are writable (CD-R, CD Recordable) and other formats that can be written to once or many times.
<DT><B><TT>CGI</TT>
</B>
<DD>Common Gateway Interface. A means of transmitting data between Web pages and programs or scripts executing on the server. Those programs can then process the data and send the results back to the user&#146;s browser through dynamically creating HTML.
<DT><B><TT>character special</TT>
</B>
<DD>A device file that is used to communicate with character-oriented I/O devices like terminals, printers, or network communications lines. All I/O access is treated as a series of bytes (characters).
<DT><B><TT>characters</TT>, <TT>alphabetic</TT>
</B>
<DD>The letters A through Z and a through z.
<DT><B><TT>characters</TT>, <TT>alphanumeric</TT>
</B>
<DD>The letters A through Z and a through z, and the numbers 0 through 9.
<DT><B><TT>characters</TT>, <TT>control</TT>
</B>
<DD>Any nonprintable characters. The characters are used to control devices, separate records, and eject pages on printers.
<DT><B><TT>characters</TT>, <TT>numeric</TT>
</B>
<DD>The numbers 0 through 9.
<DT><B><TT>characters</TT>, <TT>special</TT>
</B>
<DD>Any of the punctuation characters or printable characters that are not alphanumeric. Include the space, comma, period, and many others.
<DT><B><TT>child process</TT>
</B>
<DD>See <TT>subprocess</TT>.
<DT><B><TT>child shell</TT>
</B>
<DD>See <TT>subshell</TT>.
<DT><B><TT>class</TT>
</B>
<DD>A model of objects that have attributes (data) and behavior (code or functions). It is also viewed as a collection of objects in their abstracted form.
<DT><B><TT>command-line editing</TT>
</B>
<DD>UNIX shells support the ability to recall a previously entered command, modify it, and then execute the new version. The command history can remain between sessions (the commands you did yesterday can be available for you when you log in today). Some shells support a command-line editing mode that uses a subset of the <TT>vi</TT>, <TT>emacs</TT>, or <TT>gmacs</TT> editor commands for command recall and modification.
<DT><B><TT>command-line history</TT>
</B>
<DD>See <TT>command-line editing</TT>.
<DT><B><TT>command-line parameters</TT>
</B>
<DD>Used to specify parameters to pass to the execute program or procedure. Also known as <TT>command-line arguments</TT>.
<DT><B><TT>configuration files</TT>
</B>
<DD>Collections of information used to initialize and set up the environment for specific commands and programs. Shell configuration files set up the user&#146;s environment.
<DT><B><TT>configuration files</TT>, <TT>shell</TT>
</B>
<DD>For Bourne shell: <TT>/etc/profile</TT> and <TT>$HOME/.profile</TT>.
<BR>For Korn and <TT>pdksh</TT> shells: <TT>/etc/profile</TT>, <TT>$HOME/.profile</TT>, and <TT>ENV= file</TT>.
<BR>For C and <TT>tcsh</TT> shells:<TT> /etc/.login</TT>, <TT>/etc/cshrc</TT>, <TT>$HOME/.login</TT>, <TT>$HOME/.cshrc</TT>, and <TT>$HOME/.logout</TT>. Older versions might not support the first two files listed.
<BR>For <TT>bash</TT>: <TT>/etc/profile/</TT>, <TT>$HOME/.bash_profile</TT>, <TT>$HOME/.bash_login</TT>, <TT>$HOME/.profile</TT>, <TT>$HOME/.bashrc</TT>, and <TT>~/.bash_logout</TT>.
<DT><B><TT>CPU</TT>
</B>
<DD>Central Processing Unit. The primary &#147;brain&#148; of the computer&#151;the calculation engine and logic controller.
<DT><B><TT>daemon</TT>
</B>
<DD>A system-related background process that often runs with the permissions of root and services requests from other processes.
<DT><B><TT>DARPA</TT>
</B>
<DD>(U.S. Department of) Defense Advanced Research Projects Agency Funded development of TCP/IP and ARPAnet (predecessor of the Internet).
<DT><B><TT>database server</TT>
</B>
<DD>See <TT>server, database</TT>.
<DT><B><TT>device file</TT>
</B>
<DD>File used to implement access to a physical device. This provides a consistent approach to access of storage media under UNIX; data files and devices (like tapes and communication facilities) are implemented as files. To the programmer, there is no real difference.
<DT><B><TT>directory</TT>
</B>
<DD>A means of organizing and collecting files together. The directory itself is a file that consists of a list of files contained within it. The root (<TT>/</TT>) directory is the top level and every other directory is contained in it (directly or indirectly). A directory might contain other directories, known as <TT>subdirectories</TT>.
<DT><B><TT>directory navigation</TT>
</B>
<DD>The process of moving through directories is known as navigation. Your current directory is known as the current working directory. Your login directory is known as the default or home directory. Using the <TT>cd</TT> command, you can move up and down through the tree structure of directories.
<DT><B><TT>DNS</TT>
</B>
<DD>Domain Name Server. Used to convert between the name of a machine on the Internet (<TT>name.domain.com</TT>) to the numeric address (<TT>123.45.111.123</TT>).
<DT><B><TT>DOS</TT>
</B>
<DD>Disk Operating System Operating system that is based on the use of disks for the storage of commands. It is also a generic name for MS-DOS and PC-DOS on the personal computer. MS-DOS is the version Microsoft sells; PC-DOS is the version IBM sells. Both are based on Microsoft code.
<DT><B><TT>double</TT>
</B>
<DD>Double-precision floating point.
<DT><B><TT>dpi</TT>
</B>
<DD>Dots per inch.
<DT><B><TT>EBCDIC</TT>
</B>
<DD>Extended Binary Coded Decimal Interchange Code. The code used to represent characters in memory for mainframe computers.
<DT><B><TT>ed</TT>
</B>
<DD>A common tool used for line-oriented text editing.
<DT><B><TT>elm</TT>
</B>
<DD>Interactive mail program.
<DT><B><TT>emacs</TT>
</B>
<DD>A freely available editor now part of the GNU software distribution. Originally written by Richard M. Stallman at MIT in the late 1970s, it is available for many platforms. It is extremely extensible and has its own programming language; the name stands for editing with macros.
<DT><B><TT>email</TT>
</B>
<DD>Messages sent through an electronic medium instead of through the local postal service. There are many proprietary email systems that are designed to handle mail within a LAN environment; most of these are also able to send over the Internet. Most Internet (open) email systems make use of MIME to handle attached data (which can be binary).
<DT><B><TT>encapsulation</TT>
</B>
<DD>The process of combining data (attributes) and functions (behavior in the form of code) into an object. The data and functions are closely coupled within an object. Instead of all programmers being able to access the data in a structure their own way, they have to use the code connected with that data. This promotes code reuse and standardized methods of working with the data.
<DT><B><TT>environment variables</TT>
</B>
<DD>See <TT>variables, environmental</TT>.
<DT><B><TT>Ethernet</TT>
</B>
<DD>A networking method where the systems are connected to a single shared bus and all traffic is available to every machine. The data packets contain an identifier of the recipient, and that is the only machine that should process that packet.
<DT><B><TT>expression</TT>
</B>
<DD>A constant, variable, or operands and operators combined. Used to set a value, perform a calculation, or set the pattern for a comparison (regular expressions).
<DT><B><TT>FIFO</TT>
</B>
<DD>First In, First Out. See <TT>pipe, named</TT>.
<DT><B><TT>file</TT>
</B>
<DD>Collection of bytes stored on a device (typically a disk or tape). Can be source code, executable binaries or scripts, or data.
<DT><B><TT>file compression</TT>
</B>
<DD>The process of applying mathematical formulas to data, typically resulting in a form of the data that occupies less space. A compressed file can be uncompressed, resulting in the original file. When the compress/uncompress process results in exactly the same file as was originally compressed, it is known as lossless. If information about the original file is lost, the compression method is known as lossy. Data and programs need lossless compression; images and sounds can stand lossy compression.
<DT><B><TT>file, indexed</TT>
</B>
<DD>A file based on a file structure where data can be retrieved based on specific keys (name, employee number, and so on) or sequentially. The keys are stored in an index. This is not directly supported by the UNIX operating system; usually implemented by the programmer or by using tools from an ISV. A typical form is known as <TT>ISAM</TT>.
<DT><B><TT>file, line sequential</TT>
</B>
<DD>See <TT>file, text</TT>.
<DT><B><TT>file, sequential</TT>
</B>
<DD>This phrase can mean either a file that can only be accessed sequentially (not randomly), or a file without record separators (typically fixed length, but UNIX does not know what that length is and does not care).
<DT><B><TT>file, text</TT>
</B>
<DD>A file with record separators. Can be fixed or variable length; UNIX tools can handle these files because the tools can tell when the record ends (by the separator).
<DT><B><TT>filename</TT>
</B>
<DD>The name used to identify a collection of data (a file). Without a pathname, it is assumed to be in the current directory.
<DT><B><TT>filename generation</TT>
</B>
<DD>The process of the shell interpreting metacharacters (wildcards) to produce a list of matching files. This is referred to as filename expansion or globbing.
<DT><B><TT>filename, fully qualified</TT>
</B>
<DD>The name used to identify a collection of data (a file) and its location. It includes both the path and name of the file; typically, the pathname is fully specified (absolute). See also <TT>pathname</TT> and <TT>pathname, absolute</TT>.
<DT><B><TT>filesystem</TT>
</B>
<DD>A collection of disk storage that is connected (mounted) to the directory structure at some point (sometimes at the root). Filesystems are stored in a disk partition and are sometimes referred to as being the disk partition.
<DT><B><TT>finger</TT>
</B>
<DD>User information lookup program.
<DT><B><TT>firewall</TT>
</B>
<DD>A system used to provide a controlled entry point to the internal network from the outside (usually the Internet). This is used to prevent outside or unauthorized systems from accessing systems on your internal network. The capability depends on the individual software package, but the features typically include filter packets and filter datagrams, system (name or IP address) aliasing, and rejecting packets from certain IP addresses. In theory, it provides protection from malicious programs or people on the outside. It can also prevent internal systems from accessing the Internet on the outside. The name comes from the physical barrier between connected buildings or within a single building that is supposed to prevent fire from spreading from one to another.
<DT><B><TT>flags</TT>
</B>
<DD>See <TT>options</TT>.
<DT><B><TT>float</TT>
</B>
<DD>Single-precision floating point.
<DT><B><TT>foreground</TT>
</B>
<DD>Programs running while connected to the interactive session.
<DT><B><TT>fseek</TT>
</B>
<DD>Internal function used by UNIX to locate data inside a file or filesystem. ANSI standard <TT>fseek</TT> accepts a parameter that can hold a value of &#43;2 to -2 billion. This function, used by the operating system, system tools, and application programs, is the cause of the 2GB file and filesystem size limitation on most systems. With 64-bit operating systems, this limit is going away.
<DT><B><TT>FSF</TT>
</B>
<DD>Free Software Foundation.
<DT><B><TT>FTP</TT>
</B>
<DD>File Transfer Protocol or File Transfer Program. A system-independent means of transferring files between systems connected via TCP/IP. Ensures that the file is transferred correctly, even if there are errors during transmission. Can usually handle character set conversions (ASCII/EBCDIC) and record terminator resolution (linefeed for UNIX, carriage return and linefeed for MS/PC-DOS).
<DT><B><TT>gateway</TT>
</B>
<DD>A combination of hardware, software, and network connections that provides a link between one architecture and another. Typically, a gateway is used to connect a LAN or UNIX server with a mainframe (that uses SNA for networking, resulting in the name SNA gateway). A gateway can also be the connection between the internal and external network (often referred to as a firewall). See also <TT>firewall</TT>.
<DT><B><TT>GID</TT>
</B>
<DD>Group ID number.
<DT><B><TT>globbing</TT>
</B>
<DD>See <TT>filename generation</TT>.
<DT><B><TT>GNU</TT>
</B>
<DD>GNU stands for GNU&#146;s Not UNIX, and is the name of free useful software packages commonly found in UNIX environments that are being distributed by the GNU project at MIT, largely through the efforts of Richard Stallman. The circular acronym name (&#147;GNU&#148; containing the acronym GNU as one of the words it stands for) is a joke on Richard Stallman&#146;s part. One of the textbooks on operating system design is titled <TT>XINU: XINU Is Not UNIX</TT>, and GNU follows in that path.
<DT><B><TT>GPL</TT>
</B>
<DD>GNU General Public License.
<DT><B><TT>grep</TT>
</B>
<DD>A common tool used to search a file for a pattern. <TT>egrep</TT> and <TT>fgrep</TT> are newer versions. <TT>egrep</TT> allows the use of extended (hence the <I>e</I> prefix) regular expressions; <TT>fgrep</TT> uses limited expressions for faster (hence the <I>f</I> prefix) searches.
<DT><B><TT>GUI</TT>
</B>
<DD>Graphical user interface.
<DT><B><TT>here document</TT>
</B>
<DD>The <TT>&lt;&lt;</TT> redirection operator, known as <TT>here document</TT>, allows keyboard input (<TT>stdin</TT>) for the program to be included in the script.
<DT><B><TT>HTML</TT>
</B>
<DD>Hypertext Markup Language. Describes World Wide Web pages. It is the document language that is used to define the pages available on the Internet through the use of tags. A browser interprets the HTML to display the desired information.
<DT><B><TT>i-node</TT>
</B>
<DD>Used to describe a file and its storage. The directory contains a cross-reference between the i-node and pathname/filename combination. Also known as <TT>inode</TT>. A file&#146;s entry in disk data structure (<TT>ls -i</TT>).
<DT><B><TT>I-Phone</TT>
</B>
<DD>Internet Phone. This is a method of transmitting speech long distances over the Internet in near real-time. Participants avoid paying long distance telephone charges. They still pay for the call to their ISP and the ISP&#146;s service charges.
<DT><B><TT>ICCCM</TT>
</B>
<DD>Inter-Client Communications Conventions Manual.
<DT><B><TT>ICMP</TT>