Command Line Editing

## Command line editing and history

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 line
`ctrl-n` recall next line
`ctrl-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`

  ### WARNING

  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.