Linux shell字符操作总结

各符号介绍

字符串长度统计

• ${#string}: 字符串string的长度

字符串截取

• ${string#*substring}: 从左到右截取特定字符substring第一次出现位置之后的字符串
• ${string##*substring}:  从左到右截取特定字符substring最后一次出现位置之后的字符串
• ${string%substring*} :  从右到左截取特定字符substring第一次出现位置之后的字符串
• ${string%%substring*}:  从右到左截取特定字符substring最后一次出现位置之后的字符串
• ${string:num1:num2}:  截取从位置num1开始长度为num2的字符
• ${string:num1}: 截取从位置num1开始的字符，不指定长度，默认到字符串最后
• ${string:(-num1)}: 截取字符串尾部向前长度为num1的字符

匹配并替换

• ${string/substring/string2}: 从左到右，使用string2代替第一个匹配的substring
• ${string//substring/string2}: 从左到右，使用string2代替所有匹配的substring
• ${string/#substring/string2}: 将匹配substring的string前缀替换为string2
• ${string/%substring/string2}: 将匹配substring的string后缀替换为string2

字符串删除

• ${string/substring}: 从左到右，删除第一个匹配的substring

字母大小写转换

• ${string^^}: 将字符串string转换成大写
• ${string^^a}: 将字符串string中的字母a转换成大写
• ${string,,}: 将字符串string转换成小写
• ${string,,A}: 将字符串string中的字母A转换成小写

代码示例

~/tmp$ html="https://www.cnblogs.com/chaimy/p/17041668.html//https://www.cnblogs.com/chaimy/p/17041668.html"
#字符串长度统计
~/tmp$ echo ${#html}
94

#字符串截取
~/tmp$ echo ${html#*chai}
my/p/17041668.html//https://www.cnblogs.com/chaimy/p/17041668.html
~/tmp$ echo ${html##*chai}
my/p/17041668.html
~/tmp$ echo ${html%chai*}
https://www.cnblogs.com/chaimy/p/17041668.html//https://www.cnblogs.com/chaimy/p/17041668.html
~/tmp$ echo ${html%%chai*}
https://www.cnblogs.com/
~/tmp$ echo ${html:0:6}
https:
~/tmp$ echo ${html:1}
ttps://www.cnblogs.com/chaimy/p/17041668.html//https://www.cnblogs.com/chaimy/p/17041668.html
~/tmp$ echo ${html:(-4)}
html

#匹配并替换
~/tmp$ string="abc123abc123abc123"
~/tmp$ echo ${string/123/666}
abc666abc123abc123
~/tmp$ echo ${string//123/666}
abc666abc666abc666
~/tmp$ echo ${string/#123/666}
abc123abc123abc123
~/tmp$ echo ${string/#abc/666}
666123abc123abc123
~/tmp$ echo ${string/%123/666}
abc123abc123abc666

#字符串删除
~/tmp$ string="abc123abc123abc123"
~/tmp$ echo ${string/123}
abcabc123abc123

#字母大小写转换
~/tmp$ string="aBaC"
~/tmp$ echo ${string^^}
ABAC
~/tmp$ echo ${string^^a}
ABAC
~/tmp$ echo ${string,,}
abac
~/tmp$ echo ${string,,B}
abaC