bash中字符串的处理.txt

linux shell bash 编程

1.得到字符串长度
方法一:
$echo ${#variable}
code:
PHP 代码:
zhyfly: ~$ x="this is a test" 
zhyfly: ~$ echo ${#x} 
14 
方法二:
$expr length "$variable"
code:
PHP 代码:
zhyfly: ~$ x="this is a test" 
zhyfly: ~$ expr length "$x" 
14 
方法三:
$expr "$variable" : ".*"
code:
PHP 代码:
zhyfly: ~$ x="this is a test" 
zhyfly: ~$ expr "$x" : ".*" 
14 
2.查找字符串子串位置
方法:
$expr index "$variable" "substring"
code:
PHP 代码:
zhyfly: ~$ x="this is a test" 
zhyfly: ~$ expr index "$x" "is" 
3 
zhyfly: ~$ expr index "$x" "t" 
1 
(ps:如果出现重复,好象只能查到第一个,第二个,第三个,...,怎么查到呢???)
3.得到字符串子字符串
方法一:
$echo ${variable:position:length}
code:
PHP 代码:
zhyfly: ~$ x="this is a test" 
zhyfly: ~$ echo ${x:1:5} 
his i 
方法二:
$expr substr "$variable" startposition length
code:
PHP 代码:
zhyfly: ~$ x="this is a test" 
zhyfly: ~$ expr substr "$x" 1 5 
this 
(ps:注意方法一和方法二中位置的区别!)
4.匹配正则表达式之匹配长度
方法:
$expr match "$x" "string"
code:
PHP 代码:
zhyfly: ~$ x="this is a test" 
zhyfly: ~$ expr match "$x" "his" 
0 
zhyfly: ~$ expr match "$x" "this" 
4 
zhyfly: ~$ expr match "$x" "." 
1 
5.字符串的掐头去尾
方法:
$echo ${variable#startletter*endletter} # #表示掐头,因为键盘上#在$前面,一个表示最小匹配
$echo ${variable##tartletter*endletter} 两个表示最大匹配
$echo ${variable%startletter*endletter} # %表示去尾,因为键盘上%在$后面,一个表示最小匹配
$echo ${variable%%startletter*endletter} 两个表示最大匹配
code:
PHP 代码:
zhyfly: ~$ x="this is a test" 
zhyfly: ~$ echo ${x#t} 
his is a test 
zhyfly: ~$ echo ${x#t*h} 
is is a test 
zhyfly: ~$ echo ${x#t*s} 
is a test 

zhyfly: ~$ echo ${x##t*s} 
t 

zhyfly: ~$ echo ${x%t} 
this is a tes 
zhyfly: ~$ echo ${x%s*t} 
this is a te 
zhyfly: ~$ echo ${x%e*t} 
this is a t 

zhyfly: ~$ echo ${x%%i*t} 
th 

6.字符(串)的替换
方法:

$echo ${variable//oldletter/newletter} #替换所有
code:
PHP 代码:
zhyfly: ~$ x="this is a test" 
zhyfly: ~$ echo ${x/i/m} 
thms is a test 
zhyfly: ~$ echo ${x//i/m} 
thms ms a test