NMRPipe:EXT extract spectral region
From NMR Wiki
To extract a spectral region from 6.0-10.0 ppm use
nmrPipe -fn EXT -x1 6.0ppm -xn 10.0ppm -sw
-sw option updates change of spectral window record (if you don't use it spectral window in the resulting spectrum will be wrong)
-x1 coordinate of first point in extract region
-xn coordinate of last point in extract region