This question replaces my previous, unclear, question.

I want to use OTF fonts in XeLatex. To be concrete, here, for example, are some of the Linux Libertine fonts/fontfamilies available on my computer:

(Serif)

/usr/share/texmf-dist/fonts/opentype/public/libertine/LinBiolinum_R.otf

/usr/share/texmf-dist/fonts/opentype/public/libertine/LinBiolinum_RB.otf

/usr/share/texmf-dist/fonts/opentype/public/libertine/LinBiolinum_RBO.otf

/usr/share/texmf-dist/fonts/opentype/public/libertine/LinBiolinum_RI.otf

.....



(Sans Serif)

/usr/share/texmf-dist/fonts/opentype/public/libertine/LinLibertine_R.otf

/usr/share/texmf-dist/fonts/opentype/public/libertine/LinLibertine_I.otf

/usr/share/texmf-dist/fonts/opentype/public/libertine/LinLibertine_M.otf

/usr/share/texmf-dist/fonts/opentype/public/libertine/LinLibertine_MB.otf

....

Suppose that I want to use to able to use all of LinLibertine fonts; roman, italics etc without defining rm, it individually. Is there a simple command(s) to do this? Can one do this for both LinLibertine (serif) and LinBiolinum (sans serif) at once. I was unable to find a suitable answer to what surely is a fundamental question.

What "name" does one use in such a command and how does one know what the "name" is. In the above example is it libertine or LinLibertine or an abbreviation (such as "cm") and does the "name" have capitals?

First things first, xelatex has one mandatory package to make use of other fonts (see texdoc fontspec documentation)

usepackage{fontspec}

After that, it makes sense to define the font family name to be the part of the filename that is common across all styles (case sensitive).

In your case:

1. LinBiolinum


2. LinLibertine

Then after searching for font family in the fontspec documentation, you might think to create the two new font families like this:

Define n fonts newfontfamily

You define the command name but it makes sense to use semantically relevant names.

newfontfamilyLinBiolinum[%

  Extension = .otf , 

  UprightFont = *_R , % roman font style (segment of file path)

  ItalicFont = *_RI , % italic font style (segment of file path)

  BoldFont = *_RB , % bold font style (segment of file path)

]{LinBiolinum}



newfontfamilyLinLibertine[%

  Extension = .otf ,

  UprightFont = *_R ,

  ItalicFont = *_I ,

  BoldFont = *_MB ,

]{LinLibertine}

Then anytime you want to "activate" that font in your document, just call LinBiolinum or LinLibertine. You told fontspec how to load the different styles: bold, italic, regular:

rm = /path/LinLibertine_R.otf
it = /path/LinLibertine_RI.otf
etc.

However, fontspec uses a few built-in font family commands. The one for the main font is called normalfont, and can be manually set using setmainfont like this:

setmainfont[%

  Extension = .otf ,

  UprightFont = *_R ,

  ItalicFont = *_I ,

  BoldFont = *_MB ,

]{LinLibertine}

The way these macros work are by loading fonts based on breaking font path segments into components so that some of them may be used as variables (UprightFont, ItalicFont, BoldFont, Extension, and others listed in the fontspec documentation).

The /path/ segment is set as an environment variable. Each TeX Live Installation sets a few paths by default for its internal fonts.

cat $(kpsewhich -var-value TEXMFSYSVAR)/fonts/conf/texlive-fontconfig.conf

If you want to load a font from someplace other than those, you have two options

1. Use the Path parameter in your font family definitions


2. Add it to your path environment variable.