Print a list of all available commands and a short description about them

get-cmdlist

#!/bin/bash

# Because you never know what crazy systems are out there
if ! command -v apropos >/dev/null 2>&1; then
  apropos() { man -k "$*"; }
fi

# A small function to trim whitespace either side of a (sub)string
# shellcheck disable=SC2120
trim() {
  if [ -n "$1" ]; then
    printf -- '%s\n' "${@}" | awk '{$1=$1;print}'
  else
    awk '{$1=$1;print}'
  fi
}

cmdShortDescr() {
  # First, check with 'whatis'
  if command -v whatis >/dev/null 2>&1; then
    if whatis -r "^$1$" >/dev/null 2>&1; then
      whatis -r "^$1$" | cut -d ')' -f2- | trim | head -n 1
      return 0
    fi
  fi

  # Next, 'apropos', we assume a regex-less approach just in case
  # Otherwise, this follows the same approach as the 'whatis' method
  if apropos "$1" >/dev/null 2>&1; then
    if apropos "$1" | grep "^$1 " >/dev/null 2>&1; then
      apropos "$1" | cut -d ')' -f2- | trim | head -n 1
      return 0
    fi
  fi

  # 'help' has an output standard, the second line is what we're after
  if help "$1" >/dev/null 2>&1; then
    printf -- '- %s' "$(help "$1" | awk 'FNR==2{$1=$1;print}')"
    return 0
  fi

  # We might be dealing with a symlink, in which case
  # use 'file' to show where it links to
  if [[ -L "$(command -v "$1")" ]]; then
    printf -- '- %s' "$(file -b $(command -v "$1"))"
    return 0
  fi

  # Next we try type to catch out keywords, aliases etc
  if type "$1" >/dev/null 2>&1; then
    printf -- '- %s' "$(type "$1" | head -n 1)"
    return 0
  fi

  # If we make it to this point, no description could be found
  printf '###%s###' "Unable to find short description for '$1'"
  return 1
}

# Work our way through a sorted output of compgen -c
while read -r; do
  printf '%-30s %s\n' "${REPLY}" "$(cmdShortDescr "${REPLY}")"
done < <(compgen -c | sort | uniq)