Data l1.MD;
infile 'E:\Sasfile\f1.txt' recfm=f lrecl=32767 pad;
input text $char32767.;
run;
That would do it. RECFM=F
tells SAS to have fixed line lengths (ignoring line feeds) and the other options set the line length to the maximum for a single variable (lines can be longer, but one variable is limited to 32767 characters) and to fill it with blank spaces if it's too short.
You'd only end up with > 1 cell if your text file is longer than that. Note that the line feed and/or carriage return characters will be in this file, which may be good or may be bad. You can identify them with '0A'x and/or '0D'x (depending on your OS you may have one or both), and you can compress them with the 'c' option or translate them to a line separator of your preference.