xbd_chap03.html

IEEE 1003.1-2003, Single Unix Specification v3

<h3><a name="tag_03_83"></a>Built-In Utility (or Built-In)</h3>

<p>A utility implemented within a shell. The utilities referred to as special built-ins have special qualities. Unless qualified,
the term &quot;built-in&quot; includes the special built-in utilities. Regular built-ins are not required to be actually built into the
shell on the implementation, but they do have special command-search qualities. <basefont size="2"></p>

<dl>
<dt><b>Note:</b></dt>

<dd>Special Built-In Utilities are defined in detail in the Shell and Utilities volume of IEEE&nbsp;Std&nbsp;1003.1-2001, <a href=
"../utilities/xcu_chap02.html#tag_02_14">Section 2.14, Special Built-In Utilities</a>. 

<p>Regular Built-In Utilities are defined in detail in the Shell and Utilities volume of IEEE&nbsp;Std&nbsp;1003.1-2001, <a href=
"../utilities/xcu_chap02.html#tag_02_09_01_01">Section 2.9.1.1, Command Search and Execution</a>.</p>
</dd>
</dl>

<basefont size="3"> 

<h3><a name="tag_03_84"></a>Byte</h3>

<p>An individually addressable unit of data storage that is exactly an octet, used to store a character or a portion of a
character; see also <a href="#tag_03_87">Character</a> . A byte is composed of a contiguous sequence of 8 bits. The least
significant bit is called the &quot;low-order&quot; bit; the most significant is called the &quot;high-order&quot; bit. <basefont size="2"></p>

<dl>
<dt><b>Note:</b></dt>

<dd>The definition of byte from the ISO&nbsp;C standard is broader than the above and might accommodate hardware architectures with
different sized addressable units than octets.</dd>
</dl>

<basefont size="3"> 

<h3><a name="tag_03_85"></a>Byte Input/Output Functions</h3>

<p>The functions that perform byte-oriented input from streams or byte-oriented output to streams: <a href=
"../functions/fgetc.html"><i>fgetc</i>()</a>, <a href="../functions/fgets.html"><i>fgets</i>()</a>, <a href=
"../functions/fprintf.html"><i>fprintf</i>()</a>, <a href="../functions/fputc.html"><i>fputc</i>()</a>, <a href=
"../functions/fputs.html"><i>fputs</i>()</a>, <a href="../functions/fread.html"><i>fread</i>()</a>, <a href=
"../functions/fscanf.html"><i>fscanf</i>()</a>, <a href="../functions/fwrite.html"><i>fwrite</i>()</a>, <a href=
"../functions/getc.html"><i>getc</i>()</a>, <a href="../functions/getchar.html"><i>getchar</i>()</a>, <a href=
"../functions/gets.html"><i>gets</i>()</a>, <a href="../functions/printf.html"><i>printf</i>()</a>, <a href=
"../functions/putc.html"><i>putc</i>()</a>, <a href="../functions/putchar.html"><i>putchar</i>()</a>, <a href=
"../functions/puts.html"><i>puts</i>()</a>, <a href="../functions/scanf.html"><i>scanf</i>()</a>, <a href=
"../functions/ungetc.html"><i>ungetc</i>()</a>, <a href="../functions/vfprintf.html"><i>vfprintf</i>()</a>, and <a href=
"../functions/vprintf.html"><i>vprintf</i>()</a>. <basefont size="2"></p>

<dl>
<dt><b>Note:</b></dt>

<dd>Functions are defined in detail in the System Interfaces volume of IEEE&nbsp;Std&nbsp;1003.1-2001.</dd>
</dl>

<basefont size="3"> 

<h3><a name="tag_03_86"></a>Carriage-Return Character (&lt;carriage-return&gt;)</h3>

<p>A character that in the output stream indicates that printing should start at the beginning of the same physical line in which
the &lt;carriage-return&gt; occurred. It is the character designated by <tt>'\r'</tt> in the C language. It is unspecified whether
this character is the exact sequence transmitted to an output device by the system to accomplish the movement to the beginning of
the line.</p>

<h3><a name="tag_03_87"></a>Character</h3>

<p>A sequence of one or more bytes representing a single graphic symbol or control code. <basefont size="2"></p>

<dl>
<dt><b>Note:</b></dt>

<dd>This term corresponds to the ISO&nbsp;C standard term multi-byte character, where a single-byte character is a special case of
a multi-byte character. Unlike the usage in the ISO&nbsp;C standard, <i>character</i> here has no necessary relationship with
storage space, and <i>byte</i> is used when storage space is discussed. 

<p>See the definition of the portable character set in <a href="xbd_chap06.html#tag_06_01"><i>Portable Character Set</i></a> for a
further explanation of the graphical representations of (abstract) characters, as opposed to character encodings.</p>
</dd>
</dl>

<basefont size="3"> 

<h3><a name="tag_03_88"></a>Character Array</h3>

<p>An array of elements of type <b>char</b>.</p>

<h3><a name="tag_03_89"></a>Character Class</h3>

<p>A named set of characters sharing an attribute associated with the name of the class. The classes and the characters that they
contain are dependent on the value of the <i>LC_CTYPE</i> category in the current locale. <basefont size="2"></p>

<dl>
<dt><b>Note:</b></dt>

<dd>The <i>LC_CTYPE</i> category is defined in detail in <a href="xbd_chap07.html#tag_07_03_01"><i>LC_CTYPE</i></a> .</dd>
</dl>

<basefont size="3"> 

<h3><a name="tag_03_90"></a>Character Set</h3>

<p>A finite set of different characters used for the representation, organization, or control of data.</p>

<h3><a name="tag_03_91"></a>Character Special File</h3>

<p>A file that refers to a device. One specific type of character special file is a terminal device file. <basefont size="2"></p>

<dl>
<dt><b>Note:</b></dt>

<dd>The General Terminal Interface is defined in detail in <a href="xbd_chap11.html#tag_11"><i>General Terminal Interface</i></a>
.</dd>
</dl>

<basefont size="3"> 

<h3><a name="tag_03_92"></a>Character String</h3>

<p>A contiguous sequence of characters terminated by and including the first null byte.</p>

<h3><a name="tag_03_93"></a>Child Process</h3>

<p>A new process created (by <a href="../functions/fork.html"><i>fork</i>()</a>, <a href=
"../functions/posix_spawn.html"><i>posix_spawn</i>()</a>, or <a href="../functions/posix_spawnp.html"><i>posix_spawnp</i>()</a>) by
a given process. A child process remains the child of the creating process as long as both processes continue to exist. <basefont
size="2"></p>

<dl>
<dt><b>Note:</b></dt>

<dd>The <a href="../functions/fork.html"><i>fork</i>()</a>, <a href="../functions/posix_spawn.html"><i>posix_spawn</i>()</a>, and
<a href="../functions/posix_spawnp.html"><i>posix_spawnp</i>()</a> functions are defined in detail in the System Interfaces volume
of IEEE&nbsp;Std&nbsp;1003.1-2001.</dd>
</dl>

<basefont size="3"> 

<h3><a name="tag_03_94"></a>Circumflex</h3>

<p>The character <tt>'^'</tt> .</p>

<h3><a name="tag_03_95"></a>Clock</h3>

<p>A software or hardware object that can be used to measure the apparent or actual passage of time.</p>

<p>The current value of the time measured by a clock can be queried and, possibly, set to a value within the legal range of the
clock.</p>

<h3><a name="tag_03_96"></a>Clock Jump</h3>

<p>The difference between two successive distinct values of a clock, as observed from the application via one of the &quot;get time''
operations.</p>

<h3><a name="tag_03_97"></a>Clock Tick</h3>

<p>An interval of time; an implementation-defined number of these occur each second. Clock ticks are one of the units that may be
used to express a value found in type <b>clock_t</b>.</p>

<h3><a name="tag_03_98"></a>Coded Character Set</h3>

<p>A set of unambiguous rules that establishes a character set and the one-to-one relationship between each character of the set
and its bit representation.</p>

<h3><a name="tag_03_99"></a>Codeset</h3>

<p>The result of applying rules that map a numeric code value to each element of a character set. An element of a character set may
be related to more than one numeric code value but the reverse is not true. However, for state-dependent encodings the relationship
between numeric code values and elements of a character set may be further controlled by state information. The character set may
contain fewer elements than the total number of possible numeric code values; that is, some code values may be unassigned.
<basefont size="2"></p>

<dl>
<dt><b>Note:</b></dt>

<dd>Character Encoding is defined in detail in <a href="xbd_chap06.html#tag_06_02"><i>Character Encoding</i></a> .</dd>
</dl>

<basefont size="3"> 

<h3><a name="tag_03_100"></a>Collating Element</h3>

<p>The smallest entity used to determine the logical ordering of character or wide-character strings; see also <a href=
"#tag_03_102">Collation Sequence</a> . A collating element consists of either a single character, or two or more characters
collating as a single entity. The value of the <i>LC_COLLATE</i> category in the current locale determines the current set of
collating elements.</p>

<h3><a name="tag_03_101"></a>Collation</h3>

<p>The logical ordering of character or wide-character strings according to defined precedence rules. These rules identify a
collation sequence between the collating elements, and such additional rules that can be used to order strings consisting of
multiple collating elements.</p>

<h3><a name="tag_03_102"></a>Collation Sequence</h3>

<p>The relative order of collating elements as determined by the setting of the <i>LC_COLLATE</i> category in the current locale.
The collation sequence is used for sorting and is determined from the collating weights assigned to each collating element. In the
absence of weights, the collation sequence is the order in which collating elements are specified between <b>order_start</b> and
<b>order_end</b> keywords in the <i>LC_COLLATE</i> category.</p>

<p>Multi-level sorting is accomplished by assigning elements one or more collation weights, up to the limit {COLL_WEIGHTS_MAX}. On
each level, elements may be given the same weight (at the primary level, called an equivalence class; see also <a href=
"#tag_03_150">Equivalence Class</a> ) or be omitted from the sequence. Strings that collate equally using the first assigned weight
(primary ordering) are then compared using the next assigned weight (secondary ordering), and so on. <basefont size="2"></p>

<dl>
<dt><b>Note:</b></dt>

<dd>{COLL_WEIGHTS_MAX} is defined in detail in <a href="limits.h.html"><i>&lt;limits.h&gt;</i></a> .</dd>
</dl>

<basefont size="3"> 

<h3><a name="tag_03_103"></a>Column Position</h3>

<p>A unit of horizontal measure related to characters in a line.</p>

<p>It is assumed that each character in a character set has an intrinsic column width independent of any output device. Each
printable character in the portable character set has a column width of one. The standard utilities, when used as described in
IEEE&nbsp;Std&nbsp;1003.1-2001, assume that all characters have integral column widths. The column width of a character is not
necessarily related to the internal representation of the character (numbers of bits or bytes).</p>

<p>The column position of a character in a line is defined as one plus the sum of the column widths of the preceding characters in
the line. Column positions are numbered starting from 1.</p>

<h3><a name="tag_03_104"></a>Command</h3>

<p>A directive to the shell to perform a particular task. <basefont size="2"></p>

<dl>
<dt><b>Note:</b></dt>

<dd>Shell Commands are defined in detail in the Shell and Utilities volume of IEEE&nbsp;Std&nbsp;1003.1-2001, <a href=
"../utilities/xcu_chap02.html#tag_02_09">Section 2.9, Shell Commands</a>.</dd>
</dl>

<basefont size="3"> 

<h3><a name="tag_03_105"></a>Command Language Interpreter</h3>

<p>An interface that interprets sequences of text input as commands. It may operate on an input stream or it may interactively
prompt and read commands from a terminal. It is possible for applications to invoke utilities through a number of interfaces, which
are collectively considered to act as command interpreters. The most obvious of these are the <a href=
"../utilities/sh.html"><i>sh</i></a> utility and the <a href="../functions/system.html"><i>system</i>()</a> function, although <a
href="../functions/popen.html"><i>popen</i>()</a> and the various forms of <i>exec</i> may also be considered to behave as
interpreters. <basefont size="2"></p>

<dl>
<dt><b>Note:</b></dt>

<dd>The <a href="../utilities/sh.html"><i>sh</i></a> utility is defined in detail in the Shell and Utilities volume of
IEEE&nbsp;Std&nbsp;1003.1-2001. 

<p>The <a href="../functions/system.html"><i>system</i>()</a>, <a href="../functions/popen.html"><i>popen</i>()</a>, and
<i>exec</i> functions are defined in detail in the System Interfaces volume of IEEE&nbsp;Std&nbsp;1003.1-2001.</p>
</dd>
</dl>

<basefont size="3"> 

<h3><a name="tag_03_106"></a>Composite Graphic Symbol</h3>

<p>A graphic symbol consisting of a combination of two or more other graphic symbols in a single character position, such as a
diacritical mark and a base character.</p>

<h3><a name="tag_03_107"></a>Condition Variable</h3>

<p>A synchronization object which allows a thread to suspend execution, repeatedly, until some associated predicate becomes true. A
thread whose execution is suspended on a condition variable is said to be blocked on the condition variable.</p>

<h3><a name="tag_03_108"></a>Connection</h3>

<p>An association established between two or more endpoints for the transfer of data</p>

<h3><a name="tag_03_109"></a>Connection Mode</h3>

<p>The transfer of data in the context of a connection; see also <a href="#tag_03_110">Connectionless Mode</a> .</p>

<h3><a name="tag_03_110"></a>Connectionless Mode</h3>

<p>The transfer of data other than in the context of a connection; see also <a href="#tag_03_109">Connection Mode</a> and <a href=
"#tag_03_123">Datagram</a> .</p>

<h3><a name="tag_03_111"></a>Control Character</h3>

<p>A character, other than a graphic character, that affects the recording, processing, transmission, or interpretation of
text.</p>

<h3><a name="tag_03_112"></a>Control Operator</h3>

<p>In the shell command language, a token that performs a control function. It is one of the following symbols:</p>

<blockquote>
<pre>
<tt>&amp;   &amp;&amp;   (   )   ;   ;;   newline   |   ||
</tt>
</pre>
</blockquote>

<p>The end-of-input indicator used internally by the shell is also considered a control operator. <basefont size="2"></p>

<dl>
<dt><b>Note:</b></dt>

<dd>Token Recognition is defined in detail in the Shell and Utilities volume of IEEE&nbsp;Std&nbsp;1003.1-2001, <a href=
"../utilities/xcu_chap02.html#tag_02_03">Section 2.3, Token Recognition</a>.</dd>
</dl>

<basefont size="3"> 

<h3><a name="tag_03_113"></a>Controlling Process</h3>

<p>The session leader that established the connection to the controlling terminal. If the terminal subsequently ceases to be a
controlling terminal for this session, the session leader ceases to be the controlling process.</p>

<h3><a name="tag_03_114"></a>Controlling Terminal</h3>

<p>A terminal that is associated with a session. Each session may have at most one controlling terminal associated with it, and a
controlling terminal is associated with exactly one session. Certain input sequences from the controlling terminal cause signals to