Usage of = in Shell

If the variable is null, you can use: = to set a default value. Syntax:

 
$ {Var: = defaultvalue}
 

Example:

Enter the following command in terminal:

 
Jubincn @ Ubuntu :~ $ Echo $ {Bank: = ICBC} icbcjubincn @ Ubuntu :~ $ Echo bankicbcjubincn @ Ubuntu :~ $ Bank = ccbjubincn @ Ubuntu :~ $ Echo bankccb
 

In the following example, if the $1 parameter is not set, the die function will assign it a default value.

Die () {local error =$ {1: = undefined error} echo "$0: $ line $ error"} die "file not found" Die
 

In the preceding example, the second die function call will trigger a similar error message:

 
Bash: $1: cannot assign in this way
 

Use:-This error can be eliminated. The new die FunctionCodeAs follows:

 
Die () {local error =$ {1:-undefined error} echo "$0: $ line $ error"} die "file not found" Die
 

Note:-cannot replace: =