cheat.sh - The only cheat sheet you need

?

#!/usr/bin/env bash

cheat='curl -s cheat.sh'
menu='fzf --reverse'
pager='less -R -c'
cachefile_max_age_hours=6
explain='https://explainshell.com/explain?cmd'

# Path to temporary cache file. If your Linux system does not support /dev/shm
# or if you are on MacOS, then change the path to your liking:
cachefile='/dev/shm/cheatlist' # GNU+LINUX
# cachefile="${TMPDIR}/cheatlist"   # MacOS/Darwin

# Download list file and cache it.
listing() {
    if [ -f "${cachefile}" ]; then
        local filedate
        local now
        local age_hours
        filedate=$(stat -c %Y -- "${cachefile}")
        now=$(date +%s)
        age_hours=$(((now - filedate) / 60 / 60))
        if [[ "${age_hours}" -gt "${cachefile_max_age_hours}" ]]; then
            ${cheat}/:list >"${cachefile}"
        fi
    else
        ${cheat}/:list >"${cachefile}"
    fi
    cat -- "${cachefile}"
}

if [[ "${#}" -gt 1 ]]; then
    cmd="${*}"
    program_name="${1/ */}"
else
    cmd=""
    program_name="${1}"
fi

case "${program_name}" in
'')
    if selection=$(listing | ${menu}); then
        output="$(${cheat}/"${selection}")"
        echo "${output}" | ${pager}
        echo "${output}"
    fi
    ;;
'-h')
    # ${cheat}/:help | ${pager}
    ${cheat}/:help
    ;;
'-l')
    listing
    ;;
*)
    # ${cheat}/"${*}" | ${pager}
    ${cheat}/"${program_name}"
    ;;
esac

if [[ "${#}" -gt 1 ]]; then
    normal='\e[0m'
    whitegrey='\e[37;100m'
    echo -e "\n${whitegrey} explainshell:${cmd} ${normal}"
    w3m -dump "${explain}=${cmd}" | sed '1,9d' | grep -v '^  • ' | cat -s
fi

This case statement would allow the script to work on MacOS as well as Linux.

case "$(uname -o)" in
    GNU/Linux)  cachefile='/dev/shm/cheatlist'  ;;
    Darwin)     cachefile="$TMPDIR/cheatlist" ;;
    *)          echo "Unsupported OS"; exit 1 ;;
esac

Thank you for the suggestion. I actually would like to avoid additional checks that are always true for the current user. The variables are intended to be changed for the environment and user needs, like an option. So I will add a comment and a line ready to uncomment instead. I prefer this approach. I hope this is a good enough compromise.

Updated with additional output from https://explainshell.com, if the requested command is more than just the name of the application. The output is interpreted by terminal browser w3m and therefore is required. This is only used if the request includes any options like:

grep -v