There are many ways to intercept strings in shell
${var#*/}
${var##*/}
${var%/*}
${var%%/*}
${var:start:len}
${var:start}
${var:0-start:len}
${var:0-start}
| Format | illustrate |
|---|---|
| ${string: start :length} | Start from the start character on the left of the string string and intercept the length character to the right. |
| ${string: start} | Start from the start character on the left side of the string string until the end. |
| ${string: 0-start :length} | Start from the start character on the right of the string string and intercept the length character to the right. |
| ${string: 0-start} | Start from the start character on the right side of the string string until the end. |
| ${string#*chars} | Starting from the position where *chars first appears in the string string, intercept all characters to the right of *chars. |
| ${string##*chars} | Starting from the position where *chars last appears in the string string, intercept all characters to the right of *chars. |
| ${string%*chars} | Starting from the position where *chars first appears in the string string, intercept all characters to the left of *chars. |
| ${string%%*chars} | Starting from the position where *chars last appears in the string string, intercept all characters to the left of *chars. |
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Here are a few examples to show:
1) Get the length of the string
grammar:
${#var}
Sample code:
str="./blog/shell-truncating-string"
echo "string : [${str}]"
length=${#str}
echo "length : [${length}]"
Execution results:
string : [./blog/shell-truncating-string] length : [61]
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2) Use # and ## to get the tail substring
2.1) # Minimum number of word intercepted from the front
grammar:
${parameter#word}
Sample code:
str="./blog/shell-truncating-string"
echo "string : [${str}]"
#Segmentation character is '/'substr=${str#*/}
echo "substr : [${substr}]"
Execution results:
string : [./blog/shell-truncating-string] substr : [/./blog/shell-truncating-string]
2.2) ## Maximum intercept word from the front
grammar:
${parameter##word}
Sample code:
str="./blog/shell-truncating-string"
echo "string : [${str}]"
#Segmentation character is '/'substr=${str##*/}
echo "substr : [${substr}]"
Execution results:
string : [./blog/shell-truncating-string] substr : [shell-truncating-string]
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3) Use % and %% to get the header substring
3.1) % Minimum number of word intercepted from behind
grammar:
${parameter%word}
Sample code:
str="./blog/shell-truncating-string"
echo "string : [${str}]"
substr=${str%/*}
echo "substr : [${substr}]"
Execution results:
string : [./blog/shell-truncating-string] substr : [./blog]
3.2) %% Maximum word intercepts from the back
grammar:
${parameter%%word}
Sample code:
str="./blog/shell-truncating-string"
echo "string : [${str}]"
substr=${str%%/*}
echo "substr : [${substr}]"
Execution results:
string : [./blog/shell-truncating-string] substr : [http:]
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4) Use ${var:} mode to get substrings
4.1) Specify the number of characters in the substring starting from the left and the number of characters in the substring
grammar:
${var:start:len}
Sample code:
str="./blog/shell-truncating-string"
echo "string : [${str}]"
#The 0 indicates the start of the first character on the left, and 7 indicates the total number of sub-characters.substr=${str:0:7}
echo "substr : [${substr}]"
Execution results:
string : [./blog/shell-truncating-string] substr : [http://]
4.2) Start from the left character until the end
grammar:
${var:7}
Sample code:
str="./blog/shell-truncating-string"
echo "string : [${str}]"
#The 7 of them means the 8th character on the left startssubstr=${str:7}
echo "substr : [${substr}]"
Execution results:
string : [./blog/shell-truncating-string] substr : [./blog/shell-truncating-string]
4.3) Start from the right character and the number of characters
grammar:
${var:0-start:len}
Sample code:
str="./blog/shell-truncating-string"
echo "string : [${str}]"
#The 0-23 of them means that the 23rd character is counted on the right, and 5 means the number of characterssubstr=${str:0-23:5}
echo "substr : [${substr}]"
Execution results:
string : [./blog/shell-truncating-string] substr : [shell]
4.4) Start from the right character until the end
grammar:
${var:0-start}
Sample code:
str="./blog/shell-truncating-string"
echo "string : [${str}]"
#The 0-6 means that the 6th character is counted on the rightsubstr=${str:0-6}
echo "substr : [${substr}]"
Execution results:
string : [./blog/shell-truncating-string] substr : [string]
The above is all the content of this article. I hope it will be helpful to everyone's study and I hope everyone will support me more.