llength

length(n)                   Tcl Built-In Commands                  llength(n)
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NAME 名称
       llength - Count the number of elements in a list

SYNOPSIS 摘要
       llength list
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DESCRIPTION 描述
       Treats list as a list and returns a decimal string giving the number of elements in it.
       把列表作为一个字符串，并返回一个十进制数表示元素的数量

EXAMPLES 实例
       The result is the number of elements:

% llength {a b c d e}
5
% llength {a b c}
3
% llength {}
0

Elements are not guaranteed to be exactly words in a  dictionary  sense.of course, especially when quoting is used:
元素不能保证完全是字典里的单词，当然，特别是当使用应用时。

% llength {a b {c d} e}
4
% llength {a b { } c d e}
6

An empty list is not necessarily an empty string:
一个空列表不一定是一个空字符串

% set var { }; puts "[string length $var],[llength $var]"
1,0