How to set datadir and see all environment variables

Challenge: I want to collect all files I regularly use in a folder and use in gmt scripts without having to supply full/relative paths - just filename. The datadir variable sounds promising. But…

  • How do you set the datadir variable? This is an environment variable, right?

    $ gmt --show-datadir
    Not set


    $ gmt-config --datadir
    Not set
  • I’ve been looking in the docs, but I can’t see any definite place for where I can look up all environment variables used by gmt and that can be set. Any know where, if it exists?


In ConfigUserAdvancedTemplate.cmake I see

# Set share installation path [share or share/gmt${GMT_INSTALL_NAME_SUFFIX}]:
#set (GMT_DATADIR "share/gmt")

But assuming this really is the share dir and has nothing to do with the datadir that you get from --show-datadir;

$ gmt --show-sharedir

Suggest you look at the description of DIR variables in the manual:
The simplest sokution may be to place files in your ~/.gmt directory

1 Like

Exactly what I was looking for.

Thanks @biggle1856!

Setting GMT_DATADIR=path does what I want.

A bit curious how this relates to the datadir in,

$ gmt --show-datadir
Not set

OK, a little debugging exercise, without really using the debugger but just the fantastic VisualStudioCode search search capabilities.

Looking at gmt.c we easily find

			/* Show share directory */
			else if (!strncmp (argv[arg_n], "--show-datadir", 14U)) {
				if (api_ctrl->GMT->session.DATADIR == NULL)
					fprintf(stdout, "Not set\n");

next, I search for all occurrences of GMT->session.DATADIR in entire GMT source code and see this one in particular in gmt_init.c

	if ((this_c = getenv ("GMT_DATADIR")) != NULL) {		/* GMT_DATADIR was set */
		if (strchr (this_c, ',') || strchr (this_c, PATH_SEPARATOR)) {
			/* A list of directories [not checked for validity here] */
			GMT->session.DATADIR = strdup (this_c);

so, yes, if GMT_DATADIR is set as an environment variable you can put your files there. This is documented somewhere (didn’t search) and I also remember there was another one more tailored to store grids.

1 Like

Thanks @Joaquim for sharing. I tried grep -rn "datadir" *

If I set GMT_DATADIR, should this path show up in gmt --show-datadir?

Looking at gmt.c, it seems like it’s related to sessions, and it also refers to share directory:

                        /* Show share directory */
                        else if (!strncmp (argv[arg_n], "--show-datadir", 14U)) {
                                if (api_ctrl->GMT->session.DATADIR == NULL)
                                        fprintf(stdout, "Not set\n");
                                        fprintf(stdout, "%s\n", api_ctrl->GMT->session.DATADIR);
                                status = GMT_NOERROR;

Yes it should.

session is the structure field name where the path variable is stored. Internal stuff.

Compare that with the results of a global search in VSC