Hello everyone, this question has been soveled as follow:
[chat]
{{if|{{?text}}|{{\
{{save|chat.txt|({{time}}){{?name1}}{{if|{{?name2}}|对{{?name2}}/if}}留言:\n{{?text}}\n{{load|chat.txt}}/save}}/}}/if}}
{{if|{{{.length|{{load|chat.txt}}.}>1500}}|{{\{{save|chat.txt|{.cut||1000|{{load|chat.txt}}.}/save}}/}}/if}}
<form name=frm>
<input name=name1 size=10 value="{{?name1}}">对<input name=name2 size=10 value="{{?name2}}">留言：
<p><TEXTAREA name=text ROWS="3" COLS="40"></TEXTAREA>
<p><input type=submit value="提交留言" >
</form>
<script>document.frm.text.focus();</script>
<br><TEXTAREA ROWS="30" COLS="40">{{load|chat.txt}}</TEXTAREA>
the code is added at main, before (<form><div id='footer'>) :
<td valign=top><br><a target='bank' href="/~chat">到留言板提交留言</a>
<br><TEXTAREA ROWS="25" COLS="20">{{load|chat.txt}}</TEXTAREA>
</table>
as a resume: I found my question is at the code:
|{.cut||1000|{{load|chat.txt}}.}
after the command .cut ,there three parameters, the first is a number [Start], the second is a number [END], the third is a string, the code means: cut (keep) the characters from start to end in the string.
the related help document at this forum didnt say detail in why two || found.
thank you.
