/usr/share/mc/examples/macros.d/macro.3.sh is in mc-data 3:4.8.11-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 | #silent
S Sort selection
TMPFILE=`mktemp ${MC_TMPDIR:-/tmp}/up.XXXXXX` || exit 1
cat %b > $TMPFILE
cat $TMPFILE| sort >%b
rm -f $TMPFILE
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