shell 字串操作 + 變數替換
阿新 • • 發佈：2020-09-07
這篇部落格和我之前整理的字串處理有部分重疊 https://www.cnblogs.com/dalianpai/p/12702237.html
但是主要字串的特換還是有用，就轉載了一下。轉載：https://blog.csdn.net/zhang_referee/article/details/83511123
1.字串操作
| 表示式 | 含義 |
|---|---|
| ${#string} | 獲取字串 string 的長度 |
| ${string:position} | 從字串 string position 處擷取子串 |
| ${string:position:length} | 從字串 string position 處擷取length 長度的子串 |
| ${string#substring} | 從字串 string 的開頭，刪除最短匹配 substring 的子串 |
| ${string##substring} | 從字串 string 的開頭，刪除最長匹配 substring 的子串 |
| ${string%substring} | 從字串 string 的結尾，刪除最短匹配 substring 的子串 |
| ${string%%substring} | 從字串 string 的結尾，刪除最長匹配 substring 的子串 |
| ${string/substring/replacement} | 在字串 string 中，使用 replacement 替換 substring |
| ${string//substring/replacement} | 在字串 string 中，使用 replacement，代替所有匹配的 substring |
| ${string/#substring/replacement} | 條件替換 ： 如果字串 string 的字首匹配 substring ， 那麼就用 replacement 來代替匹配到的 substring |
| ${string/%substring/replacement} | 條件替換 ： 如果字串 string 的字尾匹配 substring ，那麼就用 replacement 來代替匹配到的 substring |
1.獲取長度：
zhang@zhang-virtual-machine:~/Desktop$ string='my blog nickName is xiao mu xi zi' zhang@zhang-virtual-machine:~/Desktop$ echo $string my blog nickName is xiao mu xi zi zhang@zhang-virtual-machine:~/Desktop$ echo ${#string} 33 zhang@zhang-virtual-machine:~/Desktop$
2.字串擷取：
zhang@zhang-virtual-machine:~/Desktop$ echo $string
my blog nickName is xiao mu xi zi
zhang@zhang-virtual-machine:~/Desktop$ echo ${string:8}
nickName is xiao mu xi zi
zhang@zhang-virtual-machine:~/Desktop$ echo ${string:8:8}
nickName
zhang@zhang-virtual-machine:~/Desktop$
3.字串替換 ：
zhang@zhang-virtual-machine:~/Desktop$ echo $string
my blog nickName is xiao mu xi zi
zhang@zhang-virtual-machine:~/Desktop$ echo ${string#my}
blog nickName is xiao mu xi zi
zhang@zhang-virtual-machine:~/Desktop$ echo ${string#my blog}
nickName is xiao mu xi zi
zhang@zhang-virtual-machine:~/Desktop$ echo ${string##my blog}
nickName is xiao mu xi zi
zhang@zhang-virtual-machine:~/Desktop$ echo ${string##zi}
my blog nickName is xiao mu xi zi
zhang@zhang-virtual-machine:~$ echo ${string%zi}
my blog nickName is xiao mu xi
zhang@zhang-virtual-machine:~$ echo ${string%%xi zi}
my blog nickName is xiao mu
zhang@zhang-virtual-machine:~$
zhang@zhang-virtual-machine:~/Desktop$ greet='hello,world,hello,linux'
zhang@zhang-virtual-machine:~/Desktop$ echo $greet
hello,world,hello,linux
zhang@zhang-virtual-machine:~/Desktop$ echo ${greet/hello/welcome to}
welcome to,world,hello,linux
zhang@zhang-virtual-machine:~/Desktop$ echo ${greet//hello/welcome to}
welcome to,world,welcome to,linux
zhang@zhang-virtual-machine:~/Desktop$ echo $greet
hello,world,hello,linux
zhang@zhang-virtual-machine:~/Desktop$ echo $greet
hello,world,hello,linux
zhang@zhang-virtual-machine:~/Desktop$ echo ${greet/#world/php}
hello,world,hello,linux
zhang@zhang-virtual-machine:~/Desktop$ echo ${greet/#hello/welcome to}
welcome to,world,hello,linux
zhang@zhang-virtual-machine:~/Desktop$ echo ${greet/%linux/php}
hello,world,hello,php
zhang@zhang-virtual-machine:~/Desktop$
2.變數替換
| 表示式 | 含義 |
|---|---|
| ${var-DEFAULT} | 如果 var 沒有被宣告，那麼就以 DEFAULT 作為其預設值 |
| ${var:-DEFAULT} | 如果var沒有被宣告或者其值為空， 那麼就以 DEFAULT 作為其預設值 |
| ${var=DEFAULT} | 如果var沒有被宣告，那麼就以 DEFAULT 作為其預設值 |
| ${var:=DEFAULT} | 如果var沒有被宣告或者其值為空，那麼就以 DEFAULT 作為其預設值 |
| ${var+OTHERVALUE} | 如果var聲明瞭， 那麼其值就是 OTHERVALUE ，否則就為空字串 |
| ${var:+OTHERVALUE} | 如果var被設定了， 那麼其值就是 OTHERVALUE ，否則就為空字串 |
| ${!varprefix*} | 匹配之前所有以varprefix開頭進行宣告的變數 |
| ${!varprefix@} | 匹配之前所有以varprefix開頭進行宣告的變數 |
zhang@zhang-virtual-machine:~/Desktop$ echo $name
zhang@zhang-virtual-machine:~/Desktop$ echo ${name-zhang}
zhang
zhang@zhang-virtual-machine:~/Desktop$ name=
zhang@zhang-virtual-machine:~/Desktop$ echo $name
zhang@zhang-virtual-machine:~/Desktop$ echo ${name:-zhang}
zhang
zhang@zhang-virtual-machine:~/Desktop$ echo ${name=zhang}
zhang@zhang-virtual-machine:~/Desktop$ echo ${name:=zhang}
zhang
zhang@zhang-virtual-machine:~/Desktop$
zhang@zhang-virtual-machine:~/Desktop$ echo $lastName
zhang@zhang-virtual-machine:~/Desktop$ echo ${lastName+guoping}
zhang@zhang-virtual-machine:~/Desktop$ lastName='xiao mu xi zi'
zhang@zhang-virtual-machine:~/Desktop$ echo ${lastName+guoping}
guoping
zhang@zhang-virtual-machine:~/Desktop$ echo ${lastName:+guoping}
guoping
zhang@zhang-virtual-machine:~/Desktop$
zhang@zhang-virtual-machine:~/Desktop$ varprefixName='zhang'
zhang@zhang-virtual-machine:~/Desktop$ varprefixLastName='guoping'
zhang@zhang-virtual-machine:~/Desktop$ fullName='guoping zhang'
zhang@zhang-virtual-machine:~/Desktop$ echo ${!varprefix*}
varprefixLastName varprefixName
zhang@zhang-virtual-machine:~/Desktop$
zhang@zhang-virtual-machine:~$ skillDynamicLanguage='php'
zhang@zhang-virtual-machine:~$ skillStaticLanguage='C++'
zhang@zhang-virtual-machine:~$ echo ${!Lanugage@}
zhang@zhang-virtual-machine:~$ echo ${!skill@}
skillDynamicLanguage skillStaticLanguage
zhang@zhang-virtual-machine:~$
以上所列，有點冷門(即用的比較少，有些系統指令碼偶爾會用到)，不過掌握後還是能省去不少麻煩。