lishell中截取字符串的方法很多
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<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">{var##/}
{var%%/}
{var:start}
{var:0-start}</pre>
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下面用几个例子展示一下：
1) 获得字符串的长度
语法：
<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">${#var}</pre>
示例代码：
<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">str="http://www.fengbohello.xin3e.com/blog/shell-truncating-string"
echo "string : [{#str} echo "length : [${length}]"</pre>
执行结果：
<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">string : [http://www.fengbohello.xin3e.com/blog/shell-truncating-string]
length : [61]</pre>
2) 使用 # 和 ## 获取尾部子字符串
2.1) # 最小限度从前面截取word
语法：
<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">${parameter#word} </pre>
示例代码：
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<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">str="http://www.fengbohello.xin3e.com/blog/shell-truncating-string"
echo "string : [{str#*/} echo "substr : [${substr}]"</pre>
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执行结果：
<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">string : [http://www.fengbohello.xin3e.com/blog/shell-truncating-string]
substr : [/www.fengbohello.xin3e.com/blog/shell-truncating-string]</pre>
2.2) ## 最大限度从前面截取word
语法：
<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">${parameter##word}</pre>
示例代码：
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<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">str="http://www.fengbohello.xin3e.com/blog/shell-truncating-string"
echo "string : [{str##*/} echo "substr : [${substr}]"</pre>
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执行结果：
<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">string : [http://www.fengbohello.xin3e.com/blog/shell-truncating-string]
substr : [shell-truncating-string]</pre>
3) 使用 % 和 %% 获取头部子字符串
3.1) % 最小限度从后面截取word
语法：
<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">${parameter%word} </pre>
示例代码：
<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">str="http://www.fengbohello.xin3e.com/blog/shell-truncating-string"
echo "string : [{str%/*}
echo "substr : [${substr}]"</pre>
执行结果：
<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">string : [http://www.fengbohello.xin3e.com/blog/shell-truncating-string]
substr : [http://www.fengbohello.xin3e.com/blog]</pre>
3.2) %% 最大限度从后面截取word
语法：
<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">${parameter%%word}</pre>
示例代码：
<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">str="http://www.fengbohello.xin3e.com/blog/shell-truncating-string"
echo "string : [{str%%/*}
echo "substr : [${substr}]"</pre>
执行结果：
<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">string : [http://www.fengbohello.xin3e.com/blog/shell-truncating-string]
substr : [http:]</pre>
4)使用 ${var:} 模式获取子字符串
4.1) 指定从左边第几个字符开始以及子串中字符的个数
语法：
<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">${var:start:len}</pre>
示例代码：
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<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">str="http://www.fengbohello.xin3e.com/blog/shell-truncating-string"
echo "string : [{str:0:7} echo "substr : [${substr}]"</pre>
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执行结果：
<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">string : [http://www.fengbohello.xin3e.com/blog/shell-truncating-string]
substr : [http://]</pre>
4.2) 从左边第几个字符开始一直到结束
语法：
<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">${var:7}</pre>
示例代码：
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<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">str="http://www.fengbohello.xin3e.com/blog/shell-truncating-string"
echo "string : [{str:7} echo "substr : [${substr}]"</pre>
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执行结果：
<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">string : [http://www.fengbohello.xin3e.com/blog/shell-truncating-string]
substr : [www.fengbohello.xin3e.com/blog/shell-truncating-string]</pre>
4.3) 从右边第几个字符开始以及字符的个数
语法：
<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">${var:0-start:len}</pre>
示例代码：
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<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">str="http://www.fengbohello.xin3e.com/blog/shell-truncating-string"
echo "string : [{str:0-23:5} echo "substr : [${substr}]"</pre>
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执行结果：
<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">string : [http://www.fengbohello.xin3e.com/blog/shell-truncating-string]
substr : [shell]</pre>
4.4) 从右边第几个字符开始一直到结束
语法：
<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">${var:0-start}</pre>
示例代码：
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<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">str="http://www.fengbohello.xin3e.com/blog/shell-truncating-string"
echo "string : [{str:0-6} echo "substr : [${substr}]"</pre>
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执行结果：
<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">string : [http://www.fengbohello.xin3e.com/blog/shell-truncating-string]
substr : [string]</pre>