Create an executable file that copies stdin to stdout, or else a script that does so through the invocation of an interpreter at the command line.

10 print chr$(147);chr$(14);
11 print "0:Keyboard  1:Tape  2:RS-232  3:Screen"
12 print "4-7:printers/plotters"
13 print "8-11:Disk Drives":print
14 input "Input device";d1
15 if d1=1 or d1>=8 then input "Filename for INPUT";i$
16 input "Output device";d2
17 if d2=1 or d2>=8 then input "Filename for OUTPUT";o$
18 print:if d1=0 then print "Begin typing. Press CTRL-Z to end.":print
20 open 5,d1,5,"0:"+i$+",s,r"
30 open 2,d2,2,"@0:"+o$+",s,w"
40 get#5,a$
50 if (d1=0 and a$=chr$(26)) or (d1>0 and st>0) then close 5:close 2:end
60 print#2,a$;
70 goto 40