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| <h5 class="subsubsection">25.3.5.2 Functions For Use in Argp Parsers</h5> |
| |
| <p>Argp provides a number of functions available to the user of argp |
| (see <a href="Argp-Parser-Functions.html#Argp-Parser-Functions">Argp Parser Functions</a>), mostly for producing error messages. |
| These take as their first argument the <var>state</var> argument to the |
| parser function. See <a href="Argp-Parsing-State.html#Argp-Parsing-State">Argp Parsing State</a>. |
| |
| <p><a name="index-usage-messages_002c-in-argp-3058"></a><!-- argp.h --> |
| <!-- GNU --> |
| |
| <div class="defun"> |
| — Function: void <b>argp_usage</b> (<var>const struct argp_state *state</var>)<var><a name="index-argp_005fusage-3059"></a></var><br> |
| <blockquote><p>Outputs the standard usage message for the argp parser referred to by |
| <var>state</var> to <var>state</var><code>->err_stream</code> and terminate the program |
| with <code>exit (argp_err_exit_status)</code>. See <a href="Argp-Global-Variables.html#Argp-Global-Variables">Argp Global Variables</a>. |
| </p></blockquote></div> |
| |
| <p><a name="index-syntax-error-messages_002c-in-argp-3060"></a><!-- argp.h --> |
| <!-- GNU --> |
| |
| <div class="defun"> |
| — Function: void <b>argp_error</b> (<var>const struct argp_state *state, const char *fmt, <small class="dots">...</small></var>)<var><a name="index-argp_005ferror-3061"></a></var><br> |
| <blockquote><p>Prints the printf format string <var>fmt</var> and following args, preceded |
| by the program name and ‘<samp><span class="samp">:</span></samp>’, and followed by a ‘<samp><span class="samp">Try ... --help</span></samp>’<!-- /@w --> message, and terminates the program with an exit status of |
| <code>argp_err_exit_status</code>. See <a href="Argp-Global-Variables.html#Argp-Global-Variables">Argp Global Variables</a>. |
| </p></blockquote></div> |
| |
| <p><a name="index-error-messages_002c-in-argp-3062"></a><!-- argp.h --> |
| <!-- GNU --> |
| |
| <div class="defun"> |
| — Function: void <b>argp_failure</b> (<var>const struct argp_state *state, int status, int errnum, const char *fmt, <small class="dots">...</small></var>)<var><a name="index-argp_005ffailure-3063"></a></var><br> |
| <blockquote><p>Similar to the standard gnu error-reporting function <code>error</code>, this |
| prints the program name and ‘<samp><span class="samp">:</span></samp>’, the printf format string |
| <var>fmt</var>, and the appropriate following args. If it is non-zero, the |
| standard unix error text for <var>errnum</var> is printed. If <var>status</var> is |
| non-zero, it terminates the program with that value as its exit status. |
| |
| <p>The difference between <code>argp_failure</code> and <code>argp_error</code> is that |
| <code>argp_error</code> is for <em>parsing errors</em>, whereas |
| <code>argp_failure</code> is for other problems that occur during parsing but |
| don't reflect a syntactic problem with the input, such as illegal values |
| for options, bad phase of the moon, etc. |
| </p></blockquote></div> |
| |
| <!-- argp.h --> |
| <!-- GNU --> |
| <div class="defun"> |
| — Function: void <b>argp_state_help</b> (<var>const struct argp_state *state, FILE *stream, unsigned flags</var>)<var><a name="index-argp_005fstate_005fhelp-3064"></a></var><br> |
| <blockquote><p>Outputs a help message for the argp parser referred to by <var>state</var>, |
| to <var>stream</var>. The <var>flags</var> argument determines what sort of help |
| message is produced. See <a href="Argp-Help-Flags.html#Argp-Help-Flags">Argp Help Flags</a>. |
| </p></blockquote></div> |
| |
| <p>Error output is sent to <var>state</var><code>->err_stream</code>, and the program |
| name printed is <var>state</var><code>->name</code>. |
| |
| <p>The output or program termination behavior of these functions may be |
| suppressed if the <code>ARGP_NO_EXIT</code> or <code>ARGP_NO_ERRS</code> flags are |
| passed to <code>argp_parse</code>. See <a href="Argp-Flags.html#Argp-Flags">Argp Flags</a>. |
| |
| <p>This behavior is useful if an argp parser is exported for use by other |
| programs (e.g., by a library), and may be used in a context where it is |
| not desirable to terminate the program in response to parsing errors. In |
| argp parsers intended for such general use, and for the case where the |
| program <em>doesn't</em> terminate, calls to any of these functions should |
| be followed by code that returns the appropriate error code: |
| |
| <pre class="smallexample"> if (<var>bad argument syntax</var>) |
| { |
| argp_usage (<var>state</var>); |
| return EINVAL; |
| } |
| </pre> |
| <p class="noindent">If a parser function will <em>only</em> be used when <code>ARGP_NO_EXIT</code> |
| is not set, the return may be omitted. |
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