If the readline library compiles on your system then the
default prompt will be ga-> as opposed to
ga>.  This indicates that command line editing is
active. The library defaults to emacs mode but can be
set up to run using vi syntax.
Here's a list of the commands which may typically be used:
ctrl-a   go to beginning of line ctrl-e   go to end of line ctrl-f   go forward one char ctrl-b   go backward one char ctrl-d   delete the char ctrl-p   recall previous linectrl-n   recall next linectrl-r   reverse search
You also get file name completion using the
tab key. If there is more than one option, then
double tab will list the available completions.
For example, suppose you are running grads on div40-2 at FNMOC and want to start looking for files to open...
Type open /h and get,
ga-> open /h
and hit two tabs and get:
h      home   home1  home2
then type ome1 and tab tab and get,
ga-> open /home1/ 
GCC         bogus603    gnu         iqpops      nmcobs      roesserd 
GRIB cstrey grads      lost+found  pacek       tsai 
Mosaic      dh          hamilton   
mendhall    picardr     witt 
NEWDBS      dolan       hout       
nicholso    qcops
then type GR, tab to go to GRIB dir, followed by d,
tab to go
to the dat dir and then n, tab tab gives,
ga-> open /home1/GRIB/dat/nogaps.25. 
nogaps.25.95021600.grb         nogaps.25.95021912.grb 
nogaps.25.95021600.gribmap     nogaps.25.95021912.gribmap 
nogaps.25.95021612.anal.grb    nogaps.25.anal.ctl 
nogaps.25.95021612.ctl         nogaps.25.anal.gribmap 
nogaps.25.95021612.grb         nogaps.25.ls.mask.ctl 
nogaps.25.95021612.gribmap     nogaps.25.ls.mask.dat 
nogaps.25.95021700.anal.grb    nogaps.25.95021700.ctl
and type 950217 to get
ga-> open /home1/GRIB/dat/nogaps.25.950217
nogaps.25.95021700.anal.grb     nogaps.25.95021712.ctl
nogaps.25.95021700.ctl          nogaps.25.95021712.grb
nogaps.25.95021700.grb          nogaps.25.95021712.gribmap
nogaps.25.95021700.gribmap    nogaps.25.95021712.anal.grb
and finally open the 12Z data with 12.c, tab,
return to open the
file
nogaps.25.95021712.ctl
There is no guarantee that these readline routines will always
work, so the -h option has been added to the invocation of GrADS
to turn them off.