21. GMT Modern Mode One-line Commands

21.1. Background

Modern mode simplifies GMT by placing all commands between gmt begin and gmt end. However, for very simple plots, such as a simple coastline map that only requires a call to a single module, having to place that command between begin and end makes the documentation longer and more tedious to maintain. Because of this, we have implemented a special and quick way to begin and end GMT modern mode within a single call to a plotting module. When the plot finishes we automatically call gmt end with the show command to display the plot(s).

21.2. One-liner Syntax

The syntax for this special mechanism involves a few simple rules:

  1. The command must be a plotting command and modern mode syntax (e.g., coast instead of pscoast, no -O, -K, -P options, etc.) is required.

  2. The plot file and type must be specified with the special option -format prefix, where format is one or more comma-separated graphics extensions from the list of allowable graphics formats formats, and prefix is the prefix of the illustration (the extension is automatically set by the chosen format). Note the leading hyphen for the format option.

  3. The one-liner command cannot itself be part of a longer modern mode session.

Note: If the single module involves a CPT (either explicitly or implicitly) then a color bar will be plotted below the map.

21.3. Examples

To make a Mercator coastline plot of France, painting land blue, adding map frame and requesting both PDF and png graphics output with prefix France1, try

gmt coast -RFR -JM6i -Gblue -B -pdf,png France1

To make a DEM map of France using the default DEM color table and data from the 1m global grid, making a JPG plot called France2, try

gmt grdimage @earth_relief_01m -RFR -JM6i -B -jpg France2

The automatic display of the plot can be deactivated by setting an environmental parameter named GMT_END_SHOW to off.