UNT;

    <I>/* &lt;perform custom checks here&gt; */</I>

    <I>/* all checks passed */</I>
    return 0;
    }</PRE><P STYLE="margin-bottom: 0cm">
Like scanfn, it should return zero for success and a user-defined
non-zero error code otherwise. These error codes are likewise
destined to be passed onto errorfn.</P>
<H4>int errorfn(void *parent, FILE *fp, int errorcode, const char
*argval, const char *progname)</H4>
<P STYLE="margin-bottom: 0.51cm">When the users wishes to print the
syntax error messages he