backticks works in ksh and the posix shell, (also called sh, just to confuse you)
a ksh specific way of doing that would be
var=$(cat text.txt)
this is nice because it nests so easily, like this
file=$(basename $(whence cat)) Mike
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"Experience is the comb that Nature gives us after we are bald."
Is that a haiku?
I never could get the hang
of writing those things.