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| <h3 class="section">10.4 Shell-Style Word Expansion</h3> |
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| <p><a name="index-word-expansion-884"></a><a name="index-expansion-of-shell-words-885"></a> |
| <dfn>Word expansion</dfn> means the process of splitting a string into |
| <dfn>words</dfn> and substituting for variables, commands, and wildcards |
| just as the shell does. |
| |
| <p>For example, when you write ‘<samp><span class="samp">ls -l foo.c</span></samp>’, this string is split |
| into three separate words—‘<samp><span class="samp">ls</span></samp>’, ‘<samp><span class="samp">-l</span></samp>’ and ‘<samp><span class="samp">foo.c</span></samp>’. |
| This is the most basic function of word expansion. |
| |
| <p>When you write ‘<samp><span class="samp">ls *.c</span></samp>’, this can become many words, because |
| the word ‘<samp><span class="samp">*.c</span></samp>’ can be replaced with any number of file names. |
| This is called <dfn>wildcard expansion</dfn>, and it is also a part of |
| word expansion. |
| |
| <p>When you use ‘<samp><span class="samp">echo $PATH</span></samp>’ to print your path, you are taking |
| advantage of <dfn>variable substitution</dfn>, which is also part of word |
| expansion. |
| |
| <p>Ordinary programs can perform word expansion just like the shell by |
| calling the library function <code>wordexp</code>. |
| |
| <ul class="menu"> |
| <li><a accesskey="1" href="Expansion-Stages.html#Expansion-Stages">Expansion Stages</a>: What word expansion does to a string. |
| <li><a accesskey="2" href="Calling-Wordexp.html#Calling-Wordexp">Calling Wordexp</a>: How to call <code>wordexp</code>. |
| <li><a accesskey="3" href="Flags-for-Wordexp.html#Flags-for-Wordexp">Flags for Wordexp</a>: Options you can enable in <code>wordexp</code>. |
| <li><a accesskey="4" href="Wordexp-Example.html#Wordexp-Example">Wordexp Example</a>: A sample program that does word expansion. |
| <li><a accesskey="5" href="Tilde-Expansion.html#Tilde-Expansion">Tilde Expansion</a>: Details of how tilde expansion works. |
| <li><a accesskey="6" href="Variable-Substitution.html#Variable-Substitution">Variable Substitution</a>: Different types of variable substitution. |
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