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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><html><head><!-- Copyright 1997 The Open Group, All Rights Reserved --><title>Glossary</title></head><body bgcolor=white><center><font size=2>The Single UNIX ® Specification, Version 2<br>Copyright © 1997 The Open Group</font></center><hr size=2 noshade><blockquote><center><h2><a name = "tag_004"> </a>Glossary</h2></center><xref type="1" name="gloss"></xref><p><h4><a name = "tag_004_000_001"> </a>absolute pathname</h4>See<xref href=pathres><a href="#tag_004_000_198">pathname resolution</a></xref>.<p><h4><a name = "tag_004_000_002"> </a>access mode</h4>A particular form of access permitted to a file.<p><h4><a name = "tag_004_000_003"> </a>additional file access control mechanism</h4>See<xref href=fileaccperm><a href="#tag_004_000_107">file access permissions</a></xref>.<p><h4><a name = "tag_004_000_004"> </a>address space</h4>The memory locations that can be referenced by a process or the threads of a process.<p><h4><a name = "tag_004_000_005"> </a>affirmative response</h4>An input string that matches one of the responsesacceptable to the LC_MESSAGES category keyword<b>yesexpr</b>,matching an extended regular expressionin the current locale;see<xref href=lc_messages><a href="locale.html#tag_005_003_006">LC_MESSAGES</a></xref>.<p><h4><a name = "tag_004_000_006"> </a>alert</h4>To cause the user's terminal to give some audibleor visual indication that an error or some other event has occurred.When the standard output is directed to a terminal device,the method for alerting the terminal user is unspecified.When the standard output is not directed to a terminal device,the alert is accomplished by writing thealertcharacter to standard output (unless the utilitydescription indicates that the use of standard outputproduces undefined results in this case).<p><h4><a name = "tag_004_000_007"> </a>alert character</h4>A character that in the output streamshould cause a terminal to alert itsuser via a visual or audible notification.Thealert characteris the character designated by'\a'in the C language.It is unspecified whether this character is the exactsequence transmitted to an output device by the system to accomplish thealert function.<p><h4><a name = "tag_004_000_008"> </a>alias name</h4>A word consisting solely of underscores, digits and alphabeticsfrom the portable character set (see<xref href=charset><a href="charset.html#tag_001_001">Portable Character Set</a></xref>)and any of the following characters:<pre><dl compact><dt> <dd>! % , @</dl></pre><p>Implementations may allow other characters within alias namesas an extension.<p><h4><a name = "tag_004_000_009"> </a>alternate file access control mechanism</h4>See<xref href=fileaccperm><a href="#tag_004_000_107">file access permissions</a></xref>.<p><h4><a name = "tag_004_000_010"> </a>alternate signal stack</h4>Memory associated with a thread, established upon request by theimplementation for a thread, separate from the thread signal stack, in whichsignal handlers responding to signals sent to that thread may be executed.<p><h4><a name = "tag_004_000_011"> </a>angle brackets</h4>The characters "<" (left-angle-bracket) and ">" (right-angle-bracket).When used in the phrase "enclosed in angle brackets", the symbol"<" immediately precedes the object to be enclosed, and ">"immediately follows it.When describing these characters inthe portable character set,the names<less-than-sign>and<greater-than-sign>are used.<p><h4><a name = "tag_004_000_012"> </a>appropriate privileges</h4><xref type="11" name="appropriv"></xref>An implementation-dependent means of associating privileges with aprocesswith regard to the function calls and function call optionsdefined in the <b>XSH</b> specification, and the commands in the <b>XCU</b> specification,that need special privileges.There may be zeroor more such means.<p><h4><a name = "tag_004_000_013"> </a>argument</h4>In the shell,a parameter passed to a utility as the equivalent of a single string in the<i>argv</i>array created by one of the<i>exec</i>functions.See<xref href=utilarg><a href="utilconv.html#tag_009_001">Utility Argument Syntax</a></xref>andthe <b>XCU</b> specification, <a href="../xcu/chap2.html#tag_001_009_001_001"><b>Command Search and Execution</b> </a>.An argument is one of theoptions, option-arguments or operands following the command name.<p>In the C language, an expression in a function callexpression or a sequence of preprocessing tokens in afunction-like macro invocation.<p><h4><a name = "tag_004_000_014"> </a>arm (a timer)</h4>To start a timermeasuring the passage of time, enabling notifying aprocess when the specified time or time interval has passed.<p><h4><a name = "tag_004_000_015"> </a>assignment</h4>See<xref href=varassign><a href="#tag_004_000_322">variable assignment</a></xref>.<p><h4><a name = "tag_004_000_016"> </a>asterisk</h4>The character "*".<p><h4><a name = "tag_004_000_017"> </a>async-cancel safe function</h4>A function that may be safely invoked by an applicationwhile the asynchronous form of cancellation is enabled.No function is async-cancel-safe unless explicitly described as such.<p><h4><a name = "tag_004_000_018"> </a>async-signal safe function</h4>A function that may be invoked, without restriction,from signal-catching functions.No function is async-signal safeunless explicitly described as such.<p><h4><a name = "tag_004_000_019"> </a>asynchronously generated signal</h4>A signal that is not attributable to a specific thread.Examples are:signals sent via<i><a href="../xsh/kill.html">kill()</a></i>,signals sent from the keyboard,and signals delivered to process groups.Being asynchronous is a property of how the signal was generatedand not a property of the signal number.All signals may be generated asynchronously.<p><h4><a name = "tag_004_000_020"> </a>asynchronous I/O operation</h4>An I/O operation that does not of itself cause the threadrequesting the I/O to be blocked from further use of the processor.<p>This implies that the process and the I/O operation may be runningconcurrently.<p><h4><a name = "tag_004_000_021"> </a>asynchronous I/O completion</h4>For an asynchronous read or write operation,when a corresponding synchronous read or write would have completedand when any associated status fields have been updated.<p><h4><a name = "tag_004_000_022"> </a>background job</h4>See<xref href=bgprocgrp><a href="#tag_004_000_024">background process group</a></xref>.<p><h4><a name = "tag_004_000_023"> </a>background process</h4>A process that is a member of a background process group.<p><h4><a name = "tag_004_000_024"> </a>background process group</h4><xref type="11" name="bgprocgrp"></xref>(Or <b>background job</b>.)Any process group, other than a foreground process group,that is a member of a session that has established a connection with acontrolling terminal.<p><h4><a name = "tag_004_000_025"> </a>backquote</h4>The character`,also known as a<i>grave accent</i>.<p><h4><a name = "tag_004_000_026"> </a>backslash</h4>The character "\", also known as a<i>reverse solidus</i>.<p><h4><a name = "tag_004_000_027"> </a>backspace character</h4>A character that,in the output stream, should cause printing (or displaying)to occur one column position previous tothe position about to be printed.If the position about to be printed is at thebeginning of the current line, the behaviour is unspecified.Thebackspaceis thecharacter designated by'\b'in the C language.It is unspecified whetherthis character is the exact sequence transmitted to an output device bythe system to accomplish the backspace function.Thebackspacecharacter definedhere is not necessarily the ERASE special character defined in<xref href=specchar><a href="termios.html#tag_008_001_009">Special Characters</a></xref>.<p><h4><a name = "tag_004_000_028"> </a>base character</h4>One of the set of characters defined in the Latin alphabet.In Western European languages other than English,these characters are commonlyused with diacritical marks (accents, cedilla, and so on) toextend the range of characters in an alphabet.<p><h4><a name = "tag_004_000_029"> </a>basename</h4>The final, or only, filename in a pathname.<p><h4><a name = "tag_004_000_030"> </a>basic regular expression</h4>A pattern constructed according tothe rules defined in<xref href=bre><a href="re.html#tag_007_003">Basic Regular Expressions</a></xref>.<p><h4><a name = "tag_004_000_031"> </a>blank character</h4>One of the characters that belong to the<b>blank</b>character classas defined via theLC_CTYPEcategory in the current locale.In the POSIX locale, ablank characteris either atabor aspace character.<p><h4><a name = "tag_004_000_032"> </a>blank line</h4><xref type="11" name="blankline"></xref>A line consisting solely of zero or moreblank charactersterminated by anewline character.See also<xref href=emptyline><a href="#tag_004_000_090">empty line</a></xref>.<p><h4><a name = "tag_004_000_033"> </a>blocked process (or thread)</h4>A process (or thread) that is waiting for some condition (other than the availability of a processor)to be satisfied before it can continue execution.<p><h4><a name = "tag_004_000_034"> </a>block-mode terminal</h4>A terminal device operating in a mode incapable of thecharacter-at-a-time input and output operationsdescribed by some of the standard utilities.See<xref href=termchar><a href="files.html#tag_003_002">Output Devices and Terminal Types</a></xref>.<p><h4><a name = "tag_004_000_035"> </a>block special file</h4>A file that refers to a device.A block special file is normally distinguished from acharacter special file by providing access to the devicein a manner such that the hardware characteristics of thedevice are not visible.<p><h4><a name = "tag_004_000_036"> </a>braces</h4>The characters "{" (left brace) and "}" (right brace),also known as<i>curly braces</i>.When used in the phrase "enclosed in (curly) braces" the symbol"{" immediately precedes the object to be enclosed, and "}"immediately follows it.When describing these characters inthe portable character set,the names<left-brace>and<right-brace>are used.<p><h4><a name = "tag_004_000_037"> </a>brackets</h4>The characters "[" (left-bracket) and "]" (right-bracket),also known as<i>square brackets</i>.When used in the phrase "enclosed in (square) brackets" the symbol"[" immediately precedes the object to be enclosed, and "]"immediately follows it.When describing these characters inthe portable character set,the names<left-square-bracket>and<right-square-bracket>are used.<p><h4><a name = "tag_004_000_038"> </a>break value</h4>The address at which dynamic memory allocation starts.<p><h4><a name = "tag_004_000_039"> </a>built-in utility</h4>(Or <b>built-in</b>.)A utility implemented within a shell.The utilities referred to as<i>special built-ins</i>have special qualities, described inthe <b>XCU</b> specification, <a href="../xcu/chap2.html#tag_001_014"><b>Special Built-in Utilities</b> </a>.Unless qualified, the term<i>built-in</i>includes the special built-in utilities.The utilities referred to as<i>regular built-ins</i>are those named inthe <b>XCU</b> specification, <a href="../xcu/chap2.html#tag_001_009_001_001"><b>Command Search and Execution</b> </a>.There is no requirement that these utilitiesbe actually built into the shell on the implementation,but they do have special command-search qualities.<p><h4><a name = "tag_004_000_040"> </a>byte</h4>An individually addressableunit of data storage that is equal to or larger than an octet,used to store a character or a portion of a character; see<xref href=character><a href="#tag_004_000_042">character</a></xref>.A byte is composed of a contiguous sequence of bits,the number of which is implementation-dependent.The least significant bit is called the<i>low-order</i>bit;the most significant is called the<i>high-order</i>bit.Note thatthis definition of<i>byte</i>deviates intentionally from the usage of<i>byte</i>⌨️ 快捷键说明
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