Changing xterm font size without a mouse

The default keybindings include what's needed:

 Shift~Ctrl <KeyPress> KP_Add:larger-vt-font() \n\ Shift Ctrl <KeyPress> KP_Add:smaller-vt-font() \n\ Shift <KeyPress> KP_Subtract:smaller-vt-font() \n\ 

That is (without any customization needed):

• shiftkeypad + switches to the next-larger font.
• shiftkeypad - switches to the next-smaller font.

There are two bindings for KP_Add to make it workable by default on some unusual keyboards.

This was originally just for bitmap-fonts (in 1999); TrueType fonts were accommodated in 2008.

It is also possible to do this with an escape-sequence, e.g.,

printf '\033]50;#+1\007' 

to switch to the next-larger font, and

printf '\033]50;#-1\007' 

to switch to the next-smaller font. The fonts.sh script in the sources makes xterm repeatedly shrink/grow, and when interrupted, restores the original font. (The \007 in the printf is a nonprinting control/G in the script to accommodate very old shells).