function box() {
  declare -i n=$1 r c;

  for ((r=0; r<n; r++)) {
    for ((c=0; c<n; c++)) {
      echo -n "*";
    }
    echo;
  }
}

# Print a 10x10 box:
box 10

function pyramid() {
  declare -i n=$1 r c s a;

  let s=n-1;
  let a=1;
  for((r=0; r<n; r++)) {
    for((c=0;c<s;c++)) { echo -n " "; }
    for((c=0;c<a;c++)) { echo -n "*"; }
    echo;
    let s--;
    let a+=2;
  }
}

#!/bin/bash

declare -i pp=1;

for p; do
  echo "$pp: $p";
  let pp++;
done

#!/bin/bash

let total=0;

# Always quote variables that may contain a filename as filenames may contain
# spaces.

# Iterates over the positional parameters, placing their values in f one at a
# time:
for f; do
  let size=$(stat -c%s "$f");
  printf "%12d %s\n" $size "$f";
  let total+=size;
done

printf "Total = %d\n" $total;

#!/bin/bash

read rows cols < <(stty size);
let row=rows/2;
let col=cols/2;
let pen=0;
tput clear;
while true
do
  tput cup $row $col;
  if (( pen )); then
    echo -n -e "#\b";
  else
    echo -n -e " \b";
  fi
  read -n 1 -s key;
  case $key in
    [wW]) if (( row )); then let row--; fi ;;
    [sS]) if (( row < rows-1 )); then let row++; fi ;;
    [aA]) if (( col )); then let col--; fi ;;
    [dD]) if (( col < cols-1 )); then let col++; fi ;;
    [qQ]) break ;;
    *) let pen^=1 ;;
  esac
done