Array inside an Array: Different syntax for Array in bash

Question

I found the following example from here. But I can't understand how is array arr is being defined.

a='domain.de;de;https'
$ arr=(${a//;/ })

What is the advantage of defining it like this?

Actually, I want to store an array inside an array of varying size like as follows:

declare -a Workspace=(
    "${Folder[0]}"  "CFD"   "General,Markdown"
    "${Folder[4]}"  "GPU"   "General,Markdown,Python,C,Java"
)

For example in above, I want to access the terms General and Markdown for CFD.

Answer 1

An array of arrays is a bad idea in shell (any shell). You need some other language.

how is array arr being defined.?

a='domain.de;de;https'
arr=(${a//;/ })

It works by:

• replacing every ; by an space
• Assuming IFS is space, tab, newline (the default)
• splitting on space (included in IFS) the unquoted expansion of ${...}
• assigning it to an array (...)
• and naming that array arr=.

What is the advantage of defining it like this?

None, only problems:

• If any of the elements contains an space, a tab or a newline, it will be split.
• As globbing was not turn off, any *, ? or [ ] will be expanded to matching files.
• If nullglob is active, any string containing *,? or [ ] will be removed.
• if failglob is active any of the previous characters will generate an error.

In short, splitting on the shell is full of gotchas.