Converting Shapefile format to text format

Is it possible to convert the shapefile to a text or DAT format in GMT?

you can plot shapefile in gmt directly using e.g. gmt plot

You can use the GDAL utility ogr2ogr to convert a shapefile to a GMT-format text file if the shapefile has points or lines. I am not sure if you can convert polygons.

You could do (which I think use ogr2ogr under the hood)

gmt convert file.shp > file.txt