Linux内置字符串处理

雨点打透心脏的1/2处 2022-07-16 14:56 152阅读 0赞

**一、字符串条件判断**

<table style="margin-left: 10.8pt; background: none repeat scroll 0% 0% #666666; width: 567px;"> 
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 <td style="width: 101.2pt; background: none repeat scroll 0% 0% #cccccc; padding: 3pt;"> 简单表达式 </td> 
 <td style="width: 132pt; background: none repeat scroll 0% 0% #cccccc; padding: 3pt;"> 解释 </td> 
 <td style="width: 189.25pt; background: none repeat scroll 0% 0% #cccccc; padding: 3pt;"> 实例 </td> 
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 <td style="width: 101.2pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> Left=${right} </td> 
 <td style="width: 132pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> Left= 变量right 的值, 与$right 相同 </td> 
 <td style="width: 189.25pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> right="a";left=${right};echo ${left} a </td> 
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 <td style="width: 101.2pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> Left=${right- DEFAULTSTRING} </td> 
 <td style="width: 132pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> 如果right 没有被声明 , 那么就以$DEFAULTSTRING 作为left 的值，否则left=$right </td> 
 <td style="width: 189.25pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> left=${right-"default"};echo $left $right default &nbsp; right="";left=${right-"default"};echo $left $right &nbsp; </td> 
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 <td style="width: 101.2pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> Left=${right:- DEFAULTSTRING} </td> 
 <td style="width: 132pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> 如果right 没有被声明, 或者其值为空 , 那么就以$DEFAULTSTRING 作left 的值，否则left=$right </td> 
 <td style="width: 189.25pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> right="";left=${right:-"default"};echo $left $right default </td> 
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 <td style="width: 101.2pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> Left=${right= DEFAULTSTRING} </td> 
 <td style="width: 132pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> 如果right 没有被声明 , 那么就以$DEFAULTSTRING 作为left 的值, 同时right=$DEFAULTSTRING, 否则left=$right </td> 
 <td style="width: 189.25pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> right="";left=${right="default"};echo $left $right &nbsp; </td> 
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 <td style="width: 101.2pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> Left=${right:= DEFAULTSTRING} </td> 
 <td style="width: 132pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> 如果right 没有被声明, 或者其值为空 , 那么就以$DEFAULTSTRING 作为left 的值, 同时right=$DEFAULTSTRING, 否则left=$right </td> 
 <td style="width: 189.25pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> right="";left=${right:="default"};echo $left $right default default </td> 
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**二、字符串常用操作（长度，读取，替换）**

<table style="width: 564px; background: none repeat scroll 0% 0% #333333;"> 
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 <td style="background: none repeat scroll 0% 0% #cccccc; padding: 3pt;"> 字符表达式 </td> 
 <td style="width: 89.9pt; background: none repeat scroll 0% 0% #cccccc; padding: 3pt;"> 解释 </td> 
 <td style="width: 132pt; background: none repeat scroll 0% 0% #cccccc; padding: 3pt;"> 实例 </td> 
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 <td style="background: none repeat scroll 0% 0% white; padding: 3pt;"> ${#string} </td> 
 <td style="width: 89.9pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> 获取$string 字符长度 </td> 
 <td style="width: 132pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> test="12345";echo ${#test} 5 </td> 
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 <td style="background: none repeat scroll 0% 0% white; padding: 3pt;"> ${string:pos} </td> 
 <td style="width: 89.9pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> 在$string 中, 从位置$pos 开始提取串(pos 从0 开始) </td> 
 <td style="width: 132pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> test="12345";echo ${test:1} 2345 </td> 
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 <td style="background: none repeat scroll 0% 0% white; padding: 3pt;"> ${string:pos:length} </td> 
 <td style="width: 89.9pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> 在$string 中, 从位置$pos 开始提取长度为$length 的串 </td> 
 <td style="width: 132pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> test="12345";echo ${test:1:2} 23 </td> 
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 <td style="background: none repeat scroll 0% 0% white; padding: 3pt;"> ${string#substring} </td> 
 <td style="width: 89.9pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> 从变量$string 左边, 删除最短匹配$substring 的串 </td> 
 <td style="width: 132pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> test="123453467";echo ${test#*3} 453467 </td> 
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 <td style="background: none repeat scroll 0% 0% white; padding: 3pt;"> ${string##substring} </td> 
 <td style="width: 89.9pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> 从变量$string 左边, 删除最长匹配$substring 的串 </td> 
 <td style="width: 132pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> test="123453467";echo ${test##*3} 467 </td> 
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 <td style="background: none repeat scroll 0% 0% white; padding: 3pt;"> ${string%substring} </td> 
 <td style="width: 89.9pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> 从变量$string 的右边开始, 删除最短匹配$substring 的串 </td> 
 <td style="width: 132pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> test="123453467";echo ${test%3*} 12345 </td> 
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 <td style="background: none repeat scroll 0% 0% white; padding: 3pt;"> ${string%%substring} </td> 
 <td style="width: 89.9pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> 从变量$string 的右边开始, 删除最长匹配$substring 的串 </td> 
 <td style="width: 132pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> test="123453467";echo ${test%%3*} 12 </td> 
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 <td style="background: none repeat scroll 0% 0% white; padding: 3pt;"> ${string/substring/replacement} </td> 
 <td style="width: 89.9pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> 使用$replacement, 来代替第一个匹配的$substring </td> 
 <td style="width: 132pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> test="123453467";echo ${test/3/9} 129 453467 </td> 
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 <td style="background: none repeat scroll 0% 0% white; padding: 3pt;"> ${string//substring/replacement} </td> 
 <td style="width: 89.9pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> 使用$replacement, 代替所有 匹配 的$substring </td> 
 <td style="width: 132pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> test="123453467";echo ${test//3/9} 129 459 467 </td> 
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 <td style="background: none repeat scroll 0% 0% white; padding: 3pt;"> ${string/#substring/replacement} </td> 
 <td style="width: 89.9pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> 如果$string 的前缀 匹配 $substring, 那么就用$replacement 来代替$substring </td> 
 <td style="width: 132pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> test="123123467";echo ${test/#123/9} 9 123467 </td> 
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 <td style="background: none repeat scroll 0% 0% white; padding: 3pt;"> ${string/%substring/replacement} </td> 
 <td style="width: 89.9pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> 如果$string 的后缀 匹配$substring, 那么就用$replacement 来代替$substring </td> 
 <td style="width: 132pt; background: none repeat scroll 0% 0% white; padding: 3pt;"> test="123123467";echo ${test/%467/9} 1231239 </td> 
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