What is quote in bash and how to use it?

In Bash, quotes are used to define how the shell interprets and treats text. They help control how variables, special characters, and whitespace are handled. There are three types of quotes commonly used in Bash: single quotes (”), double quotes (“”) and backticks (“).

1. Single Quotes (”): When you enclose text within single quotes, the shell treats it as a literal string. No variable substitution or command substitution takes place within single quotes.Example:

echo 'Hello, $USER!'   # Output: Hello, $USER!

In this example, the variable $USER is not expanded because it is within single quotes. The literal string, including the dollar sign, is printed.

2. Double Quotes (“”): Double quotes allow variable substitution and command substitution. Variables enclosed within double quotes are expanded to their values, and commands enclosed within $(...) or backticks are executed, and their output is substituted.

Example:

greeting="Hello"
echo "The greeting is: $greeting"   # Output: The greeting is: Hello

echo "Today is $(date)"   # Output: Today is <current date and time>

In this example, the variable $greeting is expanded to its value within double quotes. Similarly, the $(date) command is executed, and its output is substituted.

3. Backticks (“): Backticks (grave accents) are an older form of command substitution, which has largely been replaced by the $() syntax. They allow you to execute a command and substitute its output directly into the command line.

Example:

echo "Today is `date`"   # Output: Today is <current date and time>

1. In this example, the date command is executed within backticks, and its output is substituted.

Quotes in Bash help control the interpretation and substitution of variables and commands.

Choosing the appropriate type of quotes is important to achieve the desired behaviour in your script.