Search notes:

common options

-B 
 [a]tick[m|c]      // a=annotation, m=minutes, c=seconds (s?)
[fTICK  [m|c|l|p]] // f=frame ; l=log₁₀ ; p=10 raised to log₁₀
[gTICK  [m|c|l|p]] // g=grid intervall
[:"label":]
[:,"unit label":]
[:."title":]
[W|w]
[E|e]
[S|s]
[N|n]
-H: Input tables have header records.
-J: Map Projection.
-K: Omit postscript trailer (don't finalize post script plot). (See -K and -O)
-O: Omit postscript header (Overlay plot mode: append to existing post script plot). (See -K and -O)
-P: Use portrait plot orientation
-R: Region (min/max coordinates) of interest
use g for wrap around, see https://github.com/ReneNyffenegger/about-GMT/blob/master/Technical-Reference-and-Cookbook/4.1.1-Map-centered-on-125-E.sh
-U: Plot a timestamp (default: in the lower left corner of the page)
-V: Verbose mode
-X, -Y: shift plot for new plots.
-:: Expect latitudes/longitudes instead of longitudes/latitudes pairs while reading input.

-K and -O

The first PS producing command is to emit a postscript header, so -O is not used. It also must not emit a post script trailer, so -K is used, too
The subsequent PS producing commands except the very last one are neither to produce a PS header nor trailer, so they are given -K as well as -O.
The last PS producing command is to emit the PS trailer, so -K is not used anymore.
This results in such a sequence: 
psCommand ... -K      >  plot.ps
psCommand ... -K -O   >> plot.ps
...
psCommand ... -K -O   >> plot.ps
psCommand ...    -O   >> plot.ps

Index