unix unleashed system administrators edition phần 10 pdf

You should not use this file unless you want to ignore the directory structure ofthe device that is, if you are coding a device driver.vi The working version of the file you are editing

A device file that is used to communicate with a block oriented I/O device Disk andtape drives are examples of block devices The block-special file refers to the entiredevice You should not use this file unless you want to ignore the directory structure ofthe device (that is, if you are coding a device driver).

(vi) The working version of the file you are editing is usually called the buffer; the

buffer is actually an image of the file kept in random access memory during editing;changes are made in this image and only written out to disk upon user command (or

when the vi autowrite setting is in effect); see also named buffer and undo buffer.

buffer list

(emacs) A special window which shows all of the buffers currently open; allows you tomanipulate buffers using buffer list commands

C

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

C Shell

A user interface for UNIX written by Bill Joy at Berkeley It also features C

programming-like syntax

CD-ROM (Compact Disk-Read Only Memory)

Computer-readable data stored on the same physical form as a musical CD Largecapacity, 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

CGI (Common Gateway Interface)

A means of transmitting data between Web pages and programs or scripts executing onthe server Those programs can then process the data and send the results back to the

users browser through dynamically creating HTML.

character-special

A device file that is used to communicate with character-oriented I/O devices such asterminals, printers, or network communications lines All I/O access is treated as aseries of bytes (characters)

Any non-printable characters The characters are used to control devices, separate

records, and eject pages on printers

command line editing

UNIX shells support the ability to recall a previously entered command, modify it, andthen execute the new version The command history can remain between sessions (thecommands you did yesterday can be available for you when you log in today) Someshells support a command line editing mode that uses a subset of the vi, emacs, or

gmacs editor commands for command recall and modification

command line history

See command line editing.

command line parameters

Used to specify parameters to pass to the execute program or procedure Also known ascommand line arguments

configuration files, shell

For Bourne shell: /etc/profile and $HOME/.profile

For Korn shell: /etc/profile, $HOME/.profile, and ENV= file

For C shell: /etc/.login, /etc/cshrc, $HOME/.login, $HOME/.cshrc, and

$HOME/.logout Older versions may not support the first two files listed

For BASH: /etc/profile/, $HOME/.bash_profile, $HOME/.bash_login,

$HOME/.profile, $HOME/.bashrc, ~/.bash_logout

control keys

These are keys that cause some function to be performed instead of displaying a

character These functions have names, for instance, the end-of-file key tells the UNIXthat there is no more input The typical end-of-file key is the <^D> (control-d) key

CPU (Central Processing Unit)

The primary "brain" of the computer; the calculation engine and logic controller

current macro

(emacs) The most recently recorded macro; it is executed by the

call-last-kbd-macro function

cursor

The specific point on the screen where the next editing action will take place; the cursor

is usually indicated on the screen by some sort of highlighting, such as a underscore or asolid block, which may or may not be blinking

daemon

A system related background process that often runs with the permissions of root andservices requests from other processes

DARPA (U.S Department of Defense Advanced Research Projects Agency)

Funded development of TCP/IP and ARPAnet (predecessor of the Internet)

database server

See server, database.

default settings

Most tools and systems are governed by a number of settings; those that are in effect

when the tool is started is known as the default vi is governed by a number of settings; the default settings are those in effect when vi is first started and no automatic overrides

of settings are in effect through exrc files or EXINIT environment variables.

device file

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 (such as tapes and

communication facilities) are implemented as files To the programmer, there is no realdifference

directory

A means of organizing and collecting files together The directory itself is a file thatconsists of a list of files contained within it The root (/) directory is the top level andevery other directory is contained in it (directly or indirectly) A directory might containother directories, which are known as sub-directories

directory navigation

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 asthe default or home directory Using the cd command, you can move up and downthrough the tree structure of directories

DNS (Domain Name Server)

Used to convert the name of a machine on the Internet (name.domain.com) to the

numeric address (123.45.111.123)

DOS (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 isthe version Microsoft sells and PC-DOS is the version IBM sells Both are based onMicrosoft code.

EBCDIC (Extended Binary Coded Decimal Interchange Code)

The code used to represent characters in memory for mainframe computers

echo

The display on the screen of characters you type is sometimes called the echo of

characters; it is called this because usually your terminal is set up not to display thecharacters directly as typed, but rather to wait for them to be sent to the computer,

which then echoes (sends) them back to your terminal.

binary)

emacs

A freely available editor now part of the GNU software distribution Originally written

by Richard M Stallman at MIT in the late 1970's, it is available for many platforms It

is extremely extensible and has its own programming language; the name stands forEditing with MACroS.encapsulation The process of combining data (attributes)and functions (behavior in the form of code) into an object The data and functions areclosely coupled within an object Instead of every programmer being able to access thedata in a structure his own way, programmers have to use the code connected with thatdata This promotes code reuse and standardized methods of working with the data

environment variables

See variables, environmental.

escape

(1) (vi) The Esc key, used to terminate insert mode, or an incomplete vi command; (2)

To prevent a character from having its normal interpretation by a program by preceding

it with the escape character (usually \, the backslash); for example in a regular

expression, to search for a literal character that has a special meaning in a regular

expression, it must be escaped; as a specific example, to search for a period (.), youmust type it escaped as \

ethernet

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, which is the only machine that should process that packet

expression

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)

fifo

First In, First Out See named pipe.

file

Collection of bytes stored on a device (typically a disk or tape) Can be source code,

executable binaries or scripts, or data

1 indexed

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 ISAM

2 line sequential

See file, text.

3 sequential

a A file that can only be accessed sequentially (not randomly).

b A file without record separators Typically fixed length but UNIX does not know what thatlength is and does not care

4 text

A file with record separators May be fixed or variable length; UNIX tools can handle

these files because it can tell when the record ends (by the separator)

file compression

The process of applying mathematical formula to data typically resulting in a form of

the data that occupies less space A compressed file can be uncompressed (lossless)

resulting in the original file When the compression/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 know as lossy.

Data and programs need lossless compression; images and sounds can stand lossy

compression

filename

The name used to identify a collection of data (a file) Without a pathname, it is

assumed to be in the current directory

filename generation

The process of the shell interpreting meta-characters (wild cards) to produce a list ofmatching files This is referred to as filename expansion or globbing

filename, fully qualified

The name used to identify a collection of data (a file) and its location It includes boththe path and name of the file; typically, the pathname is fully specified (absolute) See

also pathname and pathname, absolute.

filesystem

A collection of disk storage that is connected (mounted) to the directory structure atsome point (sometimes at the root) Filesystems are stored in a disk partition and arealso referred to as disk partitions

firewall

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 systemsfrom accessing systems on your internal network The capability depends on the

individual software package, but the features typically include: filter packets, filterdatagrams, provide system (name or IP address) aliasing, and rejecting packets fromcertain IP addresses It can also prevent internal systems from accessing the Internet onthe outside In theory, it provides protection from malicious programs or people on theoutside The name comes from the physical barrier between connected buildings orwithin a single building that is supposed to prevent fire from spreading from one toanother

by the operating system, system tools, and application programs, is the cause of the 2

GB file and filesystem size limitation on most systems With 64 bit operating systems,this limit is going away

FTP (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 duringtransmission Can usually handle character set conversions (ASCII/EBCDIC) and

record terminator resolution (<lf> for UNIX, <cr> and <lf> for MS/PC-DOS)

A combination of hardware, software, and network connections that provides a linkbetween one architecture and another Typically, a gateway is used to connect a LAN orUNIX 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 firewall.

here document

The << redirection operator, known as here document, allows keyboard input (stdin)for the program to be included in the script

HTML (HyperText Markup Language)

Describes World Wide Web pages It is the document language that is used to define thepages available on the Internet through the use of tags A browser interprets the HTML

to display the desired information

i-node

Used to describes a file and its storage The directory contains a cross reference between

the i-node and pathname/filename combination Also known as inode.

I-Phone (Internet Phone)

A method of transmitting speech long distances over the Internet in near real-time

allowing the participants to avoid paying long distance telephone charges They still payfor the call to their ISP and the ISP's service charges

ICMP (Internet Control Message Protocol)

Part of TCP/IP that provides network layer management and control

inheritance

A method of object-oriented software reuse in which new classes are developed based

on existing ones by using the existing attributes and behavior and adding on to them.For example, if the base object is automobile with attributes of an engine, four wheels,and tires, and behavior of acceleration, turning, and deceleration, then a sports car

would modify the attributes so the engine would be larger or have more horsepowerthan the default, the four wheels would include alloy wheels and high speed rated tires,and the behavior would also be modified for faster acceleration, tighter turning radius,and faster deceleration

inode

See i-node.

Internet

A collection of different networks that provide the ability to move data between them It

is built on the TCP/IP communications protocol Originally developed by DARPA, itwas taken over by NSF, and has now been released from governmental control

Internet Service Provider

The people who connect you to the Internet

IRC (Internet Relay Chat)

A server-based application that allows groups of people to communicate simultaneouslythrough text-based conversations IRC is similar to Citizen Band radio or the "chatrooms" on some bulletin boards Some chats can be private (between invited peopleonly) or public (where anyone can join in) IRC now also supports sound files as well astext

it can also be useful for file exchange

ISAM (Indexed Sequential Access Method)

On UNIX and other systems, ISAM refers to a method for accessing data in a keyed orsequential way The UNIX operating system does not directly support ISAM files; theyare typically add on products

ISP

See Internet Service Provider.

ISV (Independent Software Vendor)

Generic name for software vendors other than your hardware vendor

kernel

The core of the operating system that handles tasks such as memory allocation, deviceinput and output, process allocation, security, and user access UNIX tends to have asmall kernel when compared to other operating systems

keyboard macros

A feature which allows a special key sequence to stand for another, usually more

complex sequence; in vi, keyboard macros are implemented via the :map command

kill ring

(emacs) A set of buffers where killed text is kept; the buffers are arranged in a circularpattern When commands that automatically move from one buffer to the next get to theend of the set, the next movement will be to the first buffer in the ring

Korn Shell

A user interface for UNIX with extensive scripting (programming) support Written byDavid G Korn The shell features command line editing and will also accept scriptswritten for the Bourne Shell

LAN (Local Area Network)

A collection of networking hardware, software, desktop computers, servers, and hostsall connected together within a defined local area A LAN could be an entire collegecampus

File used to implement a symbolic link producing an alias on one filesystem for a file

on another The file only contains the fully qualified filename of the original (linked-to)file

A programming language used in artificial intelligence The name stands for LISt

Processing It is the programming language that Emacs is written in and also refers to

three major modes within it

literal text string

An exact character text string, with no wildcards

(emacs) A named set of behavioral characteristics; a buffer can be in only one major

mode at a time For examples, text mode for writing a letter; c mode for writing c source

code

man page

On-line reference tool under UNIX that contains the documentation for the system theactual pages from the printed manuals It is stored in a searchable form for improvedcapability to locate information

manual page

See man page.

mappings

(vi) User-defined character sequences (which may include control keys) that are

interpreted as a command sequence (which may also include control keys)

it is using the where it is actually stored.

meta-character

A printing character that has special meaning to the shell or another command It isconverted into something else by the shell or command - the asterisk <*> is converted

by the shell to a list of all files in the current directory

MIME (Multipurpose Internet Mail Extensions)

A set of protocols or methods of attaching binary data (executable programs, images,sound files, and so on) or additional text to e-mail messages

mini-buffer

(emacs) The last line on the screen, where commands are entered

minor mode

(emacs) A particular characteristic which can be independently toggled on or off For

example, auto-fill mode for easing the creation of document text.

mode

Many programs offer only subsets of their functions at any given time, because onlycertain functions are relevant within an immediate context; further, the same keystrokemay invoke different commands in these different contexts; such a context is referred to

as a mode Major modes in vi are insert mode (for adding new text into the buffer), and command mode (for most other editing actions).

MPTN (MultiProtocol Transport Network)

IBM networking protocol to connect mainframe to TCP/IP network

named buffer

(vi)A memory location where text objects can be stored during a single vi session;

named buffers persist when you switch from one file to another during a session and are

the primary way of moving and copying text between files

named pipe

An expanded function of a regular pipe (redirecting the output of one program to

become the input of another) Instead of connecting stdout to stdin, the output of oneprogram is sent to the named pipe and another program reads data from the same file.This is implemented through a special file known as a pipe file or fifo The operatingsystem ensures the proper sequencing of the data Little or no data is actually stored inthe pipe file; it just acts as a connection between the two

Netnews

This is a loosely controlled collection of discussion groups A message (similar to ane-mail) is posted in a specific area and then people can comment on it, publicly replying

to the same place ("posting a response") for others to see A collection of messagesalong the same theme is referred to as a thread Some of the groups are moderated,which means that nothing is posted without the approval of the "owner." Most are notand the title of the group is no guarantee that the discussion will be related The

"official" term for this is Usenet News.

NFS (Network File System)

Means of connecting disks that are mounted to a remote system to the local system as ifthey were physically connected

NIS (Network Information Service)

A service that provides information necessary to all machines on a network, such asNFS support for hosts and clients, password verification, and so on

NNTP (Net News Transport Protocol)

Used to transmit Netnews or usenet messages over top of TCP/IP See Netnews for

more information on the messages transmitted

null statement

A program step that performs no operation but to hold space and fulfill syntacticalrequirements of the programming language Also known as a NO-OP for no-operationperformed

numeric setting

A setting which takes a numeric value, rather than an enabled or disabled state Applies

to many tools including vi and the different shells

object

An object in the truest sense of the word is something that has physical properties, such

as automobiles, rubber balls, and clouds These things have attributes and behavior.They can be abstracted into data (attribute) and code (behavior) Instead of just writingfunctions to work on data, they are encapsulated into a package that is known as anobject

Program- or command-specific indicators that control behavior of that program

Sometimes called flags The -a option to the ls command shows the files that begin

with a (such as profile, kshrc, and so on.) Without it, these files would not be shown,

no matter what wildcards were used These are used on the command line See also

parameters.

package

(emacs) A feature set which can be added to the editor Major modes and many

functions are implemented via packages Numerous packages are built in to standard

Emacs; many others are freely or otherwise available.

parameters

Data passed to a command or program through the command line These can be options

(see options) that control the command or arguments that the command works on Some

have special meaning based on their position on the command line

parent process identifier

Shown in the heading of the ps command as PPID The process identifier of the

parent-process See also parent-process.

parent-process

Process that controls another often referred to as the child- or sub-process See process.

parent-shell

Shell (typically the login shell) that controls another, often referred to as the child- or

sub-shell See shell.

password

The secure code that is used in combination with a user id to gain access to a UNIXsystem

pathname

The means used to represent the location of a file in the directory structure If you do

not specify a pathname, it defaults to the current directory Also see absolute pathname and relative pathname.

PDP (Personal Data Processor)

Computers manufactured by Digital Equipment Corporation UNIX was originallywritten for a PDP-7 and gained popularity on the PDP-11 The entire series were

inexpensive mini-computers popular with educational institutions and small businesses

Perl (Practical Extraction and Report Language)

Programming language developed by Larry Wall (Perl stands for "Practical Extractionand Report Language" or "Pathologically Eclectic Rubbish Language", both are equallyvalid) The language provides all of the capabilities of awk and sed, plus many of thefeatures of the shells and C

When applied to files, they are the attributes that control access to a file There are threelevels of access: owner (the file creator), group (people belonging to a related group asdetermined by the system administrator), and other (everyone else) The permissionsmay be r for read, w for write, and x for execute The execute permissions flag is alsoused to control who may search a directory

different for a station wagon and a dragster which are subclasses of the superclass

automobile The function would still be accelerate(), but the version would vary(this may sound confusing, but the compiler keeps track and figures it all out)

(vi, ed, and ex) a line address which indicates one or more lines from a starting line to

an ending line; indicated as start,end where both start and end are individual lineaddresses

RFC (Request For Comment)

Document used for creation of Internet and TCP/IP related standards

rlogin (Remote Login)

Gives the same functionality of telnet, with the added functionality of not requiring a

password from trusted clients, which can also create security concerns See telnet.

root

1) The user who owns the operating system and controls the computer 2) The processes

of the operating system run as though a user, root, signed on and started them The rootuser is all powerful and can do anything he or she wants For this reason, the root user isoften referred to as a super-user It is also the very top of the directory tree structure

The process of moving network traffic between two different physical networks; alsodecides which path to take when there are multiple connections between the two

machines It may also send traffic around transmission interruptions

RPC (Remote Procedural Call)

Provides the capability to call functions or subroutines that run on a remote system fromthe local one

scripts

A program written for a UNIX utility including shells, AWK, perl, sed, and others Also

see shell scripts.

sed

A common tool used for stream text editing, having ed-like syntax

server, database

A system designated to run database software (typically a relational database like

Oracle, SQL Server, Sybase, or others) Other systems connect to this one to get thedata (client applications)

settings

vi is governed by a number of internal variable called settings; these control how certain

actions take place

Shell

The part of UNIX that handles user input and invokes other programs to run commands

Includes a programming language See also Bourne Shell, C Shell, Korn Shell, tcsh, and BASH.

(emacs) To perform a shift-key sequence, hold down the designated shift key (for

example, Shift, Ctrl, Alt, or Meta), then press the second designated key, then release

both keys When typing several consecutive shift-key sequences that use the same shiftkey, you can keep holding down the shift key for the duration

signal

A special flag or interrupts that is used to communicate special events to programs bythe operating system and other programs

SLIP (Serial Line Internet Protocol)

Internet over a serial link (modem) The protocol frames and controls the transmission

of TCP/IP packets of the line

SNA(System Network Architecture)

IBM networking architecture

The normal input for a program, taken from the keyboard by default Can be redirected

to get input from a file or the output of another program

stdout

The normal output for a program that is sent to the screen by default Can be redirected

to a file or to the input of another program

sticky bit

One of the status flags on a file that tells UNIX to load a copy of the file into the pagefile the first time it is executed This is done for programs that are commonly used sothe bytes are available quickly When the sticky bit is used on frequently used

directories, they are cached in memory

stream

A sequential collection of data All files are streams to the UNIX operating system To

it, there is no structure to a file that is something imposed by application programs orspecial tools (ISAM packages or relational databases)

sub-directory

See directory.

Process running under the control of another, often referred to as the parent-process See

process.

sub-shell

Shell running under the control of another, often referred to as the parent-shell

(typically the login shell) See shell.

See system administrator.

TCP/IP (Transport Control Protocol/Internet Protocol)

The pair of protocols and also generic name for suite of tools and protocols that formsthe basis for the Internet Originally developed to connect systems to the ARPANET

movement command; for example w refers to the next small word.

text processing languages

A way of developing documents in text editors with embedded commands that handleformatting The file is fed through a processor that executes the embedded commandsproducing a formatted document These include roff, nroff, troff, RUNOFF, TeX,LaTeX, and even the mainframe SCRIPT

TFTP (Trivial File Transfer Protocol or Trivial File Transfer Program)

A system-independent means of transferring files between systems connected via

TCP/IP It is different from FTP in that it does not ensure that the file is transferredcorrectly, does not authenticate users, and is missing a lot of functionality (like the lscommand)

toggle

A mode that is alternately turned on and off by successive entry of its command

toggle setting

(vi) A setting which is either enabled or disabled; for example, for the fictitious setting

named option, you would enable the setting by entering the command :set option; you

would disable the setting by entering the command :set nooption

top

A common tool used to display information about the top processes on the system

typewriter key

The subset of a terminal keyboard that is on a standard typewriter; generally the

alphanumeric keys, but not the function, cursor control, or numeric pad keys

UDP (User Datagram Protocol)

Part of TCP/IP used for control messages and data transmission where the deliveryacknowledgment is not needed The application program must ensure data transmission

in this case

undo buffer

(vi) A location in memory where the most recent deleted text object is saved, either for

later undoing of the deletion, or for copying of the object to another location.

URL (Uniform Resource Locator)

The method of specifying the protocol, format, login (usually omitted), and location ofmaterials on the Internet

Usenet

See Netnews.

A place to store data and values (strings and integers) in the area controlled by the shell

so they are available to the current and sub-processes They can just be local to thecurrent shell or available to a sub-shell (exported)

Web

See World Wide Web.

whitespace

Blanks, space and tabs that are normally interpreted to delineate commands and

filenames unless quoted

wildcard

Means of specifying filename(s) where the operating system determines some of thecharacters Multiple files may match and will be available to the tool

window

The portion of your screen which is displaying a viewport into a buffer

World Wide Web

A collection of servers and services on the Internet that run software that communicateusing a common protocol (HTTP) Instead of having to remember the location of theseresources, links are provided from one Web page to another through the use of URLs(Uniform Resource Locators)

WWW

See World Wide Web.

The wrong term for the X Window System See X Window System.

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