Why does bash variable expansion retain quotes?

> echo "hi"
hi
> VAR='echo "hi"'
> $VAR
"hi"

Why is the output of the above commands different?

A similar thing occurs with single quotes:

> VAR="echo 'hi'"
> $VAR
> 'hi'

Answers:

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Method 1

The extra pair of quotes would be consumed only by an extra evaluation step. For example forced by eval:

bash-4.2$ VAR='echo "hi"'

bash-4.2$ $VAR
"hi"

bash-4.2$ eval $VAR
hi

But generally is a bad idea to put commands with parameters in one string. Use an array instead:

bash-4.2$ VAR=(echo "hi")

bash-4.2$ "${VAR[@]}"
hi

Method 2

Quote removal only occurs on the original input words, not on the result of expansions. Quotes that are part of expanded variables are untouched.

Method 3

If you step back a bit, you can see why variable substitution absolutely should retain quotes.

The point of quotes in a Unix/Linux/BSD shell is to keep pieces of a string together that would otherwise get parsed as multiple strings. Since by default a shell uses whitespace as a token separator, a string with spaces (like “one two three”) if not quoted or escaped somehow, would get parsed as 3 strings: “one”, “two” and “three”.

If a programmer wants a string with the value of some variable interpolated:

VAR=two
STRING="one $VAR three"

the shell should absolutely not remove the quotes: the string containing spaces would get parsed as 3 smaller strings.

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