Python code to generate 26 page headers for a chapter of my magnum opus:

 #!/usr/bin/env python3
 import sys
 import string
 letter = sys.argv[1].upper()
 for second in string.ascii_uppercase:
     print(f'<span style="font-size: 1.7em; font-weight: bold;">{letter}{second}</span>')

Python script to detect the width of your text and put a box around it

#!/usr/bin/env python3
import sys
lines = [line.rstrip("\n") for line in sys.stdin]
if not lines:
    sys.exit()
width = len(lines[0])
for n, line in enumerate(lines, 1):
    if len(line) > width:
        sys.exit(f"Line {n} is {len(line)} characters, exceeds box width {width}")
print("+" + "-" * (width + 2) + "+")
for line in lines:
    print(f"| {line:<{width}} |")
print("+" + "-" * (width + 2) + "+")

Skyglobe for MSDOS, still the best astronomy software 35 years later…

Before we wasted time on Windows solitaire we wasted time on MSDOS solitaire.

while :;do echo $LINES $COLUMNS $((RANDOM%COLUMNS)) $(printf '%b' "\\u$(printf '%04x' $((RANDOM%500)))");sleep .05;done|gawk '{a[$3]=0;for(x in a){o=a[x];a[x]++;printf "\033[%s;%sH\033[2;32m%s",o,x,$4;printf "\033[%s;%sH\033[1;37m%s\033[0;0H",a[x],x,$4;if(a[x]>=$1)a[x]=0}}'

Imagemagick

showcolor() { display -size 300x300 xc:"#${1}"; }

showcolor fba9c3 &

Generate magic squares for any odd side length:

#!/usr/bin/env python3
import sys
def magic_constant(n):
    return n * (n * n + 1) // 2
def magic_square(n):
    square = [[0] * n for _ in range(n)]
    num = 1
    i, j = 0, n // 2
    while num <= n * n:
        square[i][j] = num
        num += 1
        new_i = (i - 1) % n
        new_j = (j + 1) % n
        if square[new_i][new_j]:
            i = (i + 1) % n
        else:
            i, j = new_i, new_j
    return square
n = int(sys.argv[1]) if len(sys.argv) > 1 else 3
square = magic_square(n)
width = len(str(n * n))
print(f"Magic constant for n={n}: {magic_constant(n)}\n")
for row in square:
    print(" ".join(f"{x:>{width}}" for x in row))

Print a list of last Fridays every month for the given year

#!/usr/bin/python3
import sys
from calendar import monthrange
from datetime import date, timedelta
def last_fridays(year):
    for month in range(1, 13):
        last_day = date(year, month, monthrange(year, month)[1])
        yield last_day - timedelta(days=(last_day.weekday() - 4) % 7)
for friday in last_fridays(int(sys.argv[1])):
    print(friday.isoformat())

Perfect

#include <stdio.h>

int main(void)
{
    for (unsigned int p = 2; p <= 23; p++) {
        unsigned long long m = (1ULL << p) - 1;

        int prime = 1;

        for (unsigned long long i = 2; i * i <= m; i++) {
            if (m % i == 0) {
                prime = 0;
                break;
            }
        }

        if (prime)
            printf("%llu\n", (1ULL << (p - 1)) * m);
    }
}

Print a list of antiprimes (highly composite numbers) with bc

#! /usr/bin/bc
define factors(n) {
    auto c, i
    for(i=1;i<=n;i++) {
        if(n%i==0) c+=1
    }
    return c
}
max = 0
n = 1
for(c=19; c > 0;) {
    f = factors(n)
    if(f > max) {
        print n," "
        max = f
        c -= 1
    }
    n += 1
}
print "\n"
quit