c-shell3.html

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<h4 class="H4"><i><a name="84990">Variable References</a></i></h4>
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<dd><p class="Body"><a name="84992"> </a><b></b>Shell expressions may contain references to variables whose names have been entered in the system symbol table. Unless a particular type is specified with a variable reference, the variable's value in an expression is the 4-byte value at the memory address obtained from the symbol table. It is an error if an identifier in an expression is not found in the symbol table, except in the case of assignment statements discussed below.</p>
<dd><p class="Body"><a name="84993"> </a>C compilers usually prefix all user-defined identifiers with an underbar, so that <b class="symbol_lc">myVar</b> is actually in the symbol table as <b class="symbol_lc">_myVar</b>. The identifier can be entered either way to the shell--the shell searches the symbol table for a match either with or without a prefixed underbar.</p>
<dd><p class="Body"><a name="84994"> </a>You can also access data in memory that does not have a symbolic name in the symbol table, as long as you know its address. To do this, apply the C indirection operator "<b class="operator">*</b>" to a constant. For example, <b>*0x10000</b> refers to the 4-byte integer value at memory address 10000 hex.</p>
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<h4 class="H4"><i><a name="84997">Operators</a></i></h4>
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<dd><p class="Body"><a name="85143"> </a>The shell interprets the operators in <a href="c-shell3.html#85004">Table&nbsp;6-12</a> in the same way as the C compiler. <p class="table">
<h4 class="EntityTitle"><a name="85004"><font face="Helvetica, sans-serif" size="-1" class="sans">Table 6-12:&nbsp;&nbsp;Operators in the Shell C Interpreter</font></a></h4>

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<div class="CellHeading"><b><a name="85018"> </a><font face="Helvetica, sans-serif" size="-1" class="sans">Operator Type</font></b></div>

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<div class="CellHeading"><b><a name="85020"> </a><font face="Helvetica, sans-serif" size="-1" class="sans">Operators</font></b></div>

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<div class="CellBody"><a name="85046"> </a>arithmetic</div>

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<div class="CellBody"><a name="85048"> </a><b class="operator">+</b> </div>

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<div class="CellBody"><a name="85050"> </a><b class="operator">-</b> </div>

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<div class="CellBody"><a name="85052"> </a><b class="operator">*</b> </div>

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<div class="CellBody"><a name="85054"> </a><b class="operator">/</b> </div>

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<div class="CellBody"><a name="85056"> </a>unary <b class="operator">-</b> </div>

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<div class="CellBody"><a name="85060"> </a>relational</div>

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<div class="CellBody"><a name="85062"> </a><b class="operator">==</b> </div>

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<div class="CellBody"><a name="85064"> </a><b class="operator">!=</b> </div>

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<div class="CellBody"><a name="85066"> </a><b class="operator">&lt;</b> </div>

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<div class="CellBody"><a name="85068"> </a><b class="operator">&gt;</b> </div>

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<div class="CellBody"><a name="85070"> </a><b class="operator">&lt;=</b> </div>

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<div class="CellBody"><a name="85072"> </a><b class="operator">&gt;=</b> </div>

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<div class="CellBody"><a name="85074"> </a>shift</div>

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<div class="CellBody"><a name="85076"> </a><b class="operator">&lt;&lt;</b> </div>

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<div class="CellBody"><a name="85078"> </a><b class="operator">&gt;&gt;</b> </div>

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<div class="CellBody"><a name="85080"> </a></div>

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<div class="CellBody"><a name="85082"> </a></div>

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<div class="CellBody"><a name="85084"> </a></div>

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<div class="CellBody"><a name="85086"> </a></div>

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<div class="CellBody"><a name="85088"> </a>logical</div>

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<div class="CellBody"><a name="85090"> </a><b class="operator">||</b> </div>

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<div class="CellBody"><a name="85092"> </a><b class="operator">&amp;&amp;</b> </div>

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<div class="CellBody"><a name="85094"> </a><b class="operator">!</b> </div>

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<div class="CellBody"><a name="85096"> </a></div>

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<div class="CellBody"><a name="85098"> </a></div>

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<div class="CellBody"><a name="85100"> </a></div>

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<div class="CellBody"><a name="85102"> </a>bitwise</div>

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<div class="CellBody"><a name="85104"> </a><b class="operator">|</b> </div>

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<div class="CellBody"><a name="85106"> </a><b class="operator">&amp;</b> </div>

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<div class="CellBody"><a name="85108"> </a><b class="operator">~</b> </div>

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<div class="CellBody"><a name="85110"> </a><b class="operator">^</b> </div>

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<div class="CellBody"><a name="85112"> </a></div>

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<div class="CellBody"><a name="85116"> </a>address and indirection</div>

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<div class="CellBody"><a name="85118"> </a><b class="operator">&amp;</b> </div>

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<div class="CellBody"><a name="85120"> </a><b class="operator">*</b> </div>

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<div class="CellBody"><a name="85122"> </a></div>

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