>
  <i>stringnumber</i>  Number of the required substring
  <i>buffer</i>        Buffer to receive the string
  <i>buffersize</i>    Size of buffer
</pre>
The yield is the length of the string, PCRE_ERROR_NOMEMORY if the buffer was
too small, or PCRE_ERROR_NOSUBSTRING if the string number is invalid.
</P>
<P>
There is a complete description of the PCRE native API in the
<a href="pcreapi.html"><b>pcreapi</b></a>
page and a description of the POSIX API in the
<a href="pcreposix.html"><b>pcreposix</b></a>
page