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The way the expansion happens is not how you would expect.

test -v X[$index]

Does not expand to:

test -v X["a'b"]

But instead it expands like this:

test -v 'X[a'\''b]'

bash splits and escapes the array syntax in a way that prevents test -v from seeing a valid array element. test -v expects a fully valid variable name or array element as a single argument.

As Kusalananda suggested you could use test -v 'X[$index]' however I think a much more correct way would be to use the extended test syntax instead:

if [[ -n $index && -v 'X[$index]' ]]; then

The way the expansion happens is not how you would expect.

test -v X[$index]

Does not expand to:

test -v X["a'b"]

But instead it expands like this:

test -v 'X[a'\''b]'

bash splits and escapes the array syntax in a way that prevents test -v from seeing a valid array element. test -v expects a fully valid variable name or array element as a single argument.

As Kusalananda suggested you could use test -v 'X[$index]' however I think a much more correct way would be to use the extended test syntax instead:

if [[ -v X["$index"] ]]; then

The way the expansion happens is not how you would expect.

test -v X[$index]

Does not expand to:

test -v X["a'b"]

But instead it expands like this:

test -v 'X[a'\''b]'

bash splits and quotes the array syntax in a way that prevents test -v from seeing a valid array element. test -v expects a fully valid variable name or array element as a single argument.

As Kusalananda suggested you could use test -v 'X[$index]' however I think a much more correct way would be to use the extended test syntax instead:

if [[ -n $index && -v 'X[$index]' ]]; then

The way the expansion happens is not how you would expect.

test -v X[$index]

Does not expand to:

test -v X["a'b"]

But instead it expands like this:

test -v 'X[a'\''b]'

bash splits and escapes the array syntax in a way that prevents test -v from seeing a valid array element. test -v expects a fully valid variable name or array element as a single argument.

As Kusalananda suggested you could use test -v 'X[$index]' however I think a much more correct way would be to use the extended test syntax instead:

if [[ -n $index && -v 'X[$index]' ]]; then

The way the expansion happens is not how you would expect.

test -v X[$index]

Does not expand to:

test -v X["a'b"]

But instead it expands like this:

test -v 'X[a'\''b]'

bash splits and quotes the array syntax in a way that prevents test -v from seeing a valid array element. test -v expects a fully valid variable name or array element as a single argument.

As Kusalananda suggested you could use test -v 'X[$index]' however I think a much more correct way would be to use the extended test syntax instead:

if [[ -v X[$index] ]]; then

The way the expansion happens is not how you would expect.

test -v X[$index]

Does not expand to:

test -v X["a'b"]

But instead it expands like this:

test -v 'X[a'\''b]'

bash splits and quotes the array syntax in a way that prevents test -v from seeing a valid array element. test -v expects a fully valid variable name or array element as a single argument.

As Kusalananda suggested you could use test -v 'X[$index]' however I think a much more correct way would be to use the extended test syntax instead:

if [[ -n $index && -v 'X[$index]' ]]; then