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| <h4 class="subsection">25.3.8 Customizing Argp Help Output</h4> |
| |
| <p>The <code>help_filter</code> field in a <code>struct argp</code> is a pointer to a |
| function that filters the text of help messages before displaying |
| them. They have a function signature like: |
| |
| <pre class="smallexample"> char *<var>help-filter</var> (int <var>key</var>, const char *<var>text</var>, void *<var>input</var>) |
| </pre> |
| <p class="noindent">Where <var>key</var> is either a key from an option, in which case <var>text</var> |
| is that option's help text. See <a href="Argp-Option-Vectors.html#Argp-Option-Vectors">Argp Option Vectors</a>. Alternately, one |
| of the special keys with names beginning with ‘<samp><span class="samp">ARGP_KEY_HELP_</span></samp>’ |
| might be used, describing which other help text <var>text</var> will contain. |
| See <a href="Argp-Help-Filter-Keys.html#Argp-Help-Filter-Keys">Argp Help Filter Keys</a>. |
| |
| <p>The function should return either <var>text</var> if it remains as-is, or a |
| replacement string allocated using <code>malloc</code>. This will be either be |
| freed by argp or zero, which prints nothing. The value of <var>text</var> is |
| supplied <em>after</em> any translation has been done, so if any of the |
| replacement text needs translation, it will be done by the filter |
| function. <var>input</var> is either the input supplied to <code>argp_parse</code> |
| or it is zero, if <code>argp_help</code> was called directly by the user. |
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| <ul class="menu"> |
| <li><a accesskey="1" href="Argp-Help-Filter-Keys.html#Argp-Help-Filter-Keys">Keys</a>: Special <var>key</var> values for help filter functions. |
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