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- <a name="Inept-excess-verbiage"></a>
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- <a name="Inept-excess-verbiage-1"></a>
- <h4 class="subsubsection">3.9.3.1 Inept excess verbiage</h4>
- <p>Although the author of a library function may take pride in putting
- its activities on display, it should be assumed that virtual code
- applications running on <code>avram</code> have other agendas for the
- console, so the library interface module should prevent direct output
- from the external library.
- </p>
- <p>More thoughtful API’s may have a verbosity setting, which should be
- <a name="index-verbosity-setting"></a>
- used in preference to this workaround, but failing that, it is easy to
- dispense with console output generated by calls to external library
- functions by using some combination of the following functions.
- </p>
- <dl>
- <dt><a name="index-avm_005fturn_005foff_005fstdout"></a><u>Function:</u> void <b>avm_turn_off_stdout</b><i> ()</i></dt>
- <dd><p>Calling this function will suppress all output to the standard output
- stream until the next time <code>avm_turn_on_stdout</code> is called.
- Additional calls to this function without intervening calls to
- <code>avm_turn_on_stdout</code> may be made safely with no effect. The
- standard output stream is flushed as a side effect of calling this
- function.
- </p></dd></dl>
- <dl>
- <dt><a name="index-avm_005fturn_005fon_005fstdout"></a><u>Function:</u> void <b>avm_turn_on_stdout</b><i> ()</i></dt>
- <dd><p>Calling this function will allow output to the standard output
- stream to resume if it has been suppressed previously by a call to
- <code>avm_turn_off_stdout</code>. If <code>avm_turn_off_stdout</code> has not been
- previously called, this function has no effect. Any output that would
- have been sent to <code>stdout</code> during the time it was turned off will
- be lost.
- </p></dd></dl>
- <dl>
- <dt><a name="index-avm_005fturn_005foff_005fstderr"></a><u>Function:</u> void <b>avm_turn_off_stderr</b><i> ()</i></dt>
- <dd><p>This function performs a similar service to that of
- <code>avm_turn_off_stdout</code> but pertains to the standard error stream.
- The standard error and the standard output streams are controlled
- independently even if both of them are piped to the same console.
- </p></dd></dl>
- <dl>
- <dt><a name="index-avm_005fturn_005fon_005fstderr"></a><u>Function:</u> void <b>avm_turn_on_stderr</b><i> ()</i></dt>
- <dd><p>This function performs a similar service to that of
- <code>avm_turn_on_stdout</code> but pertains to the standard error stream.
- </p></dd></dl>
- <p>As an example, the following code fragment will prevent any output to
- standard output taking place as a side effect of <code>blather</code>, but
- will allow error messages to standard error. Note that ouput should
- not be left permanently turned off.
- </p>
- <table><tr><td> </td><td><pre class="example">...
- #include <avm/mwrap.h>
- ...
- x = y + z;
- avm_turn_off_stdout ();
- w = blather (foo, bar, baz);
- avm_turn_on_stdout ();
- return w;
- ...
- </pre></td></tr></table>
- <p>One possible issue with these functions is that they rely on a
- feature of the GNU C library that might not be portable to non-GNU
- <a name="index-portability"></a>
- systems and has not been widely tested on other platforms.
- </p>
- <p>Another issue is that a library function could be both careless enough
- to clutter the console unconditionally and meticulous enough to check
- for I/O errors after each attempted write. Writing while the output
- stream is disabled will return an I/O error to the caller (i.e., to
- the verbose library function) for appropriate action, which could
- include terminating the process.
- </p>
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