Shell Learning 11-shell String

Strings are the most common and useful data types in shell programming (except numbers and strings, and no other type works well), strings can be in single quotes or double quotes, or without quotes. The difference between single and double quotes is similar to PHP.
single quotation marks

Str= ' This is a string '

Single-Quote String restrictions:
Any character in a single quotation mark is output as is, and the variable in the single-quote string is not valid;
Single quotation marks cannot appear in single quote strings (not after using escape characters for single quotes).
Double quotes

Your_name= ' QINJX ' str= "Hello, I know your is \" $your _name\ "! \ n "

Advantages of double quotes:
You can have variables in double quotes.
Escape characters can appear in double quotes
Stitching Strings

Your_name= "QINJX" greeting= "Hello," $your _name "!" greeting_1= "Hello, ${your_name}!" echo $greeting $greeting _1

Get string length

string= "ABCD" Echo ${#string} #输出 4

Extract substring

String= "Alibaba is a great company" Echo ${string:1:4} #输出liba

Finding substrings

String= "Alibaba is a great company" Echo ' Expr index "$string" is "

Shell Learning 11-shell String