§2023-09-09

In Bash, you can assign values to variables in several ways:

• Direct Assignment: You can assign a value directly to a variable using the = operator. For example:

  • my_var="Hello, World!"

• Command Substitution: You can assign the output of a command to a variable using command substitution, as shown in your original example:

  • my_var=$(command)

• Using read: You can use the read command to read input from the user or from a file and assign it to a variable. For example:

  • read my_var

• Array Assignment: In Bash, you can also work with arrays. You can assign values to an array using parentheses:

$ my_array=("apple" "banana" "cherry")
$ my_array=("apple" "banana" "cherry")
$ echo "${my_array[2]}"
cherry
$ echo "${my_array[0]}"
apple
alexlai@Surfa

• Environment Variables: You can assign environment variables to Bash variables. Environment variables are typically uppercase, and you can access them using the $ symbol:

MY_ENV_VAR="This is an environment variable"
my_var="$MY_ENV_VAR"

• Default Values with :-: You can assign a default value to a variable using the :- operator. If the variable is not set or is empty, it will be assigned the default value:

$ my_var="${MY_DEFAULT_VAR:-Default Value}"
$ echo $my_var
Default Value

• Appending to a Variable: You can append to an existing variable using the += operator:

$ my_var+=" more text"
$ echo $my_var
Default Value more text

• Using Arithmetic: You can perform arithmetic operations and assign the result to a variable:

$ num1=5
$ num2=3
$ result=$((num1 + num2))
$ echo $result 
8