Using mapfile on the output of another command [duplicate]

Question

I want to edit a file before feeding it into an array. The data file contains:

Line 1 Line 2 Line 3

If I read it with

mapfile -t direct < data

I obtain a 3-element direct array

But I pipe the output of a sed command the edited array is empty:

sed s:Line:LINE: data | mapfile -t edited

As far as I can tell the sed output is fine (lines with LF separators) and replacing sed with a cat command doesn't improve things anyway.

What am I missing?

See related Why is my variable local in one 'while read' loop, but not in another seemingly similar loop? — steeldriver
– steeldriver, Commented Apr 28 at 9:21

xenoid · Accepted Answer · 2025-04-28 09:38:34Z

OK, thanks to @steeldriver, I saw the error in my ways. The mapfile must not be in a subshell, so this can be rewritten as:

 mapfile -t edited < <(sed s:Line:LINE: data)

and edited gets the expected contents.

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