Urxvt ~/.Xresources not reading/loading

The setterm utility is intended for use with the Linux console. According to the console_codes manual page:

The Linux console implements a large subset of the VT102 and ECMA-48/ISO 6429/ANSI X3.64 terminal controls, plus certain private- mode sequences for changing the color palette, character-set mapping, and so on.

Since the program is hard-coded,

/* -regtabs. */
if (ctl->opt_regtabs && vc_only(ctl, "--regtabs")) {
    int i;

    fputs("\033[3g\r", stdout);
    for (i = ctl->opt_rt_len + 1; i <= TABS_MAX; i += ctl->opt_rt_len)
        printf("\033[%dC\033H", ctl->opt_rt_len);
    putchar('\r');
}

it just happens to work with xterm since xterm implements VT100 controls (plus more).

As for large subset, that is debatable. In a quick count of the items in console_codes, I see 79 control sequences. That is far less than any of the xterm look-alikes documented in the xterm FAQ Comparing versions, by counting controls. By itself, 79 is not large. The VT102 itself (not an xterm look-alike) had 104. ISO-6429 (aka ECMA-48) documents 20 modes and 162 sequences. Whether you count the total as 182 or 162, 50% is not a large subset.

Rather than using a Linux console utility, there is a more portable choice: the tabs utility (in POSIX as well as Solaris). It is part of the ncurses utilities (and probably installed on your Linux system).

For the example given in the question, you could do this:

tabs -4

That uses the terminal database, rather than being hard-coded. Tabs and the control sequences to set them are documented in ECMA-48 and other places such as the terminfo(5) manual page.

And tabs works with xterm.

If no fonts are specified in .Xdefaults, .xresources or on the command line, the default single-byte font rxvt uses is 7x14.

From the file src/defaultfont.h in the rxvt source:

82 #define NFONT_LIST \
83   "7x14", "6x10", "6x13", "8x13", "8x16", "10x20", "12x24"

These fonts are loaded into the default rxvt font set in their respective positions when nothing has been specified for that position. Note that if you use a multi-byte encoding, there is a different default.

In response to the comment below, I cannot say for sure whether that is 6x13 or not, all I can point to is this logic in defaultfont.c

300  if (encoding >= ENC_ISO8859_1 && encoding <= ENC_ISO8859_LAST) {
301    /* fallback for ISO-8859-* encodings */
302    k = encoding - ENC_ISO8859_1 + 1;
303    MIN_IT(k, 99999);
304  } else
305    /* fallback for "C", "POSIX", and invalid locales */
306    k = 0;
 :
308   for (j = 0; j < MAX_NFONTS; j++) {
309     if (rs[Rs_font + j] == NULL) {
310       if (k == 0)
311       rs[Rs_font + j] = def_fontName[j];
312     else {
313       /* couple of wasted bytes each but lots of future expansion */
314       rs[Rs_font + j] = rxvt_malloc(STRLEN(defaultfont_8859[j]) + 4);
315       sprintf((char *)rs[Rs_font + j], defaultfont_8859[j], k);
316     }
317   }

If the locale is C the Rs_font[0] is 7x14 and Rs_font[2] is 6x13. When and where [0] vs [2] are used to render text is beyond my motivation to search through this unfamiliar code.

If the encoding is not C/POSIX, the 8859 fonts loaded by the above code are:

#define NFONT_LIST_ISO8859X \
"-misc-fixed-medium-r-normal--14-130-75-75-c-70-iso8859-%d",       /*xf*/ \
"-misc-fixed-medium-r-normal--10-100-75-75-c-60-iso8859-%d",       /*xf*/ \
"-misc-fixed-medium-r-semicondensed--13-120-75-75-c-60-iso8859-%d",/*xf*/ \
"-misc-fixed-medium-r-normal--13-120-75-75-c-80-iso8859-%d",       /*xf*/ \
"-misc-fixed-medium-r-normal--16-120-100-100-c-80-iso8859-%d",     /*xf*/ \
"-misc-fixed-medium-r-normal--20-200-75-75-c-100-iso8859-%d",      /*xf*/ \
"-misc-fixed-medium-r-normal--24-170-100-100-c-120-iso8859-%d"     /*xf*/

And if multi-byte encodings are in use, a whole different encoding specific set of fonts are used for the default.