Command Substitution

On a keyboard, there is one interesting key, the backward quote,`. This key isnormallysituated below theEsckey. If we place text between two successive backquotes, thenechowill execute those as commands instead of processing them as plain text.

Alternate syntax for$(command)is the backtick character`, which we can see as follows:

$(command) or `command`

For example:

• We need to use proper double quotes, as follows:

$ echo "Hello, whoami"

• The next command will print the text as it is; such asHello, whoami:

Output:

Hello, whoami

• Use proper double quotes and single backquotes:

$ echo "Hello, `whoami`."Hello, student

• When we enclosewhoamitext in the`characters, the same text that was printed as plain text will run as a command, and command output will be printed on the screen.

• Use proper double quotes:

$ echo "Hello, $(whoami)."Hello, student.

• This is the same as earlier.

Another example:

$ echo "Today is date"

Output:

Today is date

A similar example:

/

Another example is:

$ echo "Today is...