Need to document all ldmsd -c configuration file capabilities!

[morrone]

Apparently the ldmsd configuration file, the one specified on the command line through the "-c" option, has some very powerful undocumented options. Namely:

• Environment variable substitution: ${SOMEVAR}
• Command subtitution: $(echo foo)
• The "env" directive to set environment variables for use in variable substitution: env VAR=VALUE

I only discovered these capabilities by accident in an example on this wiki page:

https://github.com/ovis-hpc/ovis/wiki/Example-Configuration-Scripts-%28v4%29#Sampler_configuration_file_samplerconf

But an example is not sufficient. These things need to be documented clearly with the rest of the configuration file options in the appropriate man page(s).

These capabilities could be game changers for us. There is a good chance that this will be sufficient to let us eliminate the complicated genders scripting solution that ldms provides and replace it with something much easier to handle.

[morrone]

Point me to where that was documented in the code?