[gradsusr] How to export variable as text file

[Inoue Kazunori]

Dear Sir,

By the following ctl file, I can display the rainfall data (precip) in
a world map form. Could you advise me how to export the precip of a
specific area to text (ascii) file ?
the ctl file is as follows,

DSET ^gsmap_nrt.%y4%m2%d2.0.25d.daily.00Z-23Z.dat
TITLE GSMaP_NRT 0.25deg Daily (00:00Z-23:59Z)
UNDEF -999.9
OPTIONS YREV LITTLE_ENDIAN TEMPLATE
XDEF 1440 LINEAR    0.125 0.25
YDEF 480 LINEAR  -59.875 0.25
zdef 1 levels 1013
tdef 3650 linear 00:00z1dec2007 1dy
VARS 1
precip          0 99 daily averaged precip(mm/hr)
ENDVARS

I assume that at first I can specify the range of longitude and
latitude, and export command something.
Any help is highly appreciated.

-- 
Inoue Kazunori