TMUX/Byobu status bar: CPU+MEM usage bars in only 4 chars

01_cpu_mem_bars

#!/usr/bin/env python3
# Byobu custom status script: CPU + MEM as colored UTF-8 block chars.
# Install: place in ~/.byobu/bin/01_cpu_mem_bars and chmod +x
# Enable:  add 'custom' to tmux_right in ~/.byobu/status
#
# Integration — vanilla tmux (~/.tmux.conf):
#   set -g status-right '#(~/.byobu/bin/01_cpu_mem_bars)%H:%M:%S'
#
# Integration — byobu (~/.byobu/profile.tmux):
#   source $BYOBU_PREFIX/share/byobu/profiles/tmux
#   set -g status-right '#(byobu-status tmux_right)#(~/.byobu/bin/01_cpu_mem_bars)%H:%M:%S'
#
# Output examples (as seen in byobu status bar):
#   c▁m▂   CPU ~10% (cyan), MEM ~20% (cyan) — all quiet
#   c▃M▆   CPU ~25% (cyan), MEM ~70% (yellow) — memory notable
#   C▅M▇   CPU ~60% (yellow), MEM ~85% (red) — both busy
#   C█M█   CPU ~95% (red), MEM ~95% (red) — under pressure
#   C▆M!   MEM ≥95% — memory alarm: M! in white bold on red background
#
# Letter is uppercase when usage > 50%, lowercase otherwise.
# Colors: cyan <30%, green 30-60%, yellow 60-85%, red >85%
import os, time

CACHE = os.path.join(os.environ.get('TMPDIR', '/tmp'), 'proc_stat.last')

def cpu_pct():
    cur = [int(x) for x in open('/proc/stat').readline().split()[1:]]
    try:
        prev = [int(x) for x in open(CACHE).read().split()]
        cached_time = os.path.getmtime(CACHE)
    except OSError:
        cached_time, prev = 0, cur
    total = sum(cur) - sum(prev)
    # Write cache only when stale or on counter wrap — avoids redundant writes
    # when multiple byobu status processes run close together each second.
    # time.time() is called here, as close as reasonable to cache write.
    if time.time() - cached_time > 1 or total <= 0:
        with open(CACHE, 'w', encoding="utf-8") as cache:
            cache.write(' '.join(map(str, cur)))
    if total <= 0:
        return 0
    idle  = (cur[3] + cur[4]) - (prev[3] + prev[4])
    return (total - idle) * 100 // total

def mem_pct():
    info = {}
    for line in open('/proc/meminfo'):
        k, v = line.split()[0].rstrip(':'), int(line.split()[1])
        info[k] = v
        if 'MemTotal' in info and 'MemAvailable' in info: break
    return (info['MemTotal'] - info['MemAvailable']) * 100 // info['MemTotal']

def fmt(pct):
    color = 'red' if pct > 85 else 'yellow' if pct > 60 else 'green' if pct > 30 else 'cyan'
    bar   = chr(0x2580 + max(1, pct * 8 // 100))
    return color, bar

cpu = cpu_pct()
mem = mem_pct()
cc, cb = fmt(cpu)
cl = 'C' if cpu > 50 else 'c'
if mem >= 95:
    mem_part = '#[bg=red,fg=white,bold]M!'
else:
    mc, mb = fmt(mem)
    ml = 'M' if mem > 50 else 'm'
    mem_part = f'#[fg={mc}]{ml}{mb}'

print(f'\033#[fg=black,bg=default]▐#[fg={cc},bg=black]{cl}{cb}{mem_part}#[fg=black,bg=default]▌#[default]', end='')