Uncorrectly read file

[1micha.elok]

Question
Case 1 : I think ... [for...next] is not the best way to read text file
Case 2 : I think this is the best way, but [do..until frln(f) = "unset"] gives unexpectedly output

Please advice me what is the best way to read the whole text file ?
Thank you.

Code:

set window "readfile",400,400

f = openfile("story.txt")

'Case 1
'correctly read file
for i = 0 to 21
    wln frln(f)
    i = i + 1
next

'Case 2
'uncorrectly read file
do
    wln frln(f)
until frln(f)="unset"

free file f

temp=rln()