Read the first line with the C1 .... in it and use that to calculate the starting locations for this version of the file.
Let's convert one of your example files into a physical file we can reference in the example code.
options parmcards=txt ;
filename txt temp;
parmcards4;
C1 C2 C3 c4 c5 c6 c7 c8
aaaa z8z 23 bbbbbbbbbbbbb s;lfjslf;sjl;dkfjs y ls;dkfjl ;ds n abc xyz
;;;;
Now let's read that first line and pick out the variable names and their start and end columns.
data start;
length col start end 8 name next $32;
infile txt obs=1 column=cc truncover;
start=1;
input name @;
do col=1 by 1 until(next=' ');
input next @ ;
end = cc - lengthn(next) - 2;
output;
name=next;
start = end+1;
end;
list;
drop next;
run;
Result:
Obs col start end name
1 1 1 13 C1
2 2 14 26 C2
3 3 27 79 C3
4 4 80 119 c4
5 5 120 143 c5
6 6 144 165 c6
7 7 166 171 c7
8 8 172 173 c8
Note that the end column for that last one might be a little off as the length of the NAME is probably shorter than the length of the values in the last column.
We can use that to write the input statement to read your file.
filename code temp;
data _null_;
set start end=eof;
file code;
if _n_=1 then put 'input ' ;
put @3 name '$' start '-' end ;
if eof then put ';' ;
run;
data want;
infile txt firstobs=2 truncover ;
%include code / source2;
run;
