envdir-compare

#!/bin/bash
# 
# Try different dirs each with the following contents to observe differences in
# implementations.
#   
#   file "abc" with contents "A\nB\nC\n"
#   file "xyz" with contents "X\0Y\0Z\n"
#   file "e" with contents "\nEEE\n"
#   empty file "x=y"
#   file "x=y" with contents "Z"
#   empty directory "d"
#   directory "d" with file "f"
#   empty directory "d" when there's "d=1" in the calling environment already
# 
declare -A envdirs=(
    [daemontools]=/usr/bin/envdir   # https://cr.yp.to/daemontools/envdir.html
    [python]=~/.local/bin/envdir    # https://pypi.org/project/envdir/
    [tsibley]=~/bin/envdir          # https://github.com/tsibley/envdir
)

envd="${1:?usage: envdir-compare <envd> [<cmd> [<args>…]]}"
shift

for impl in $(printf '%s\n' "${!envdirs[@]}" | sort); do (
    envdir="${envdirs[$impl]}"

    if [[ $# -gt 0 ]]; then
        set -- "$envdir" "$envd" "$@"
    else
        set -- env --ignore-environment "$envdir" "$envd" perl -MJSON::PP -E 'say encode_json(\%ENV)'
    fi

    echo $'\e[1m'"[$impl] $@"$'\e[m'
    "$@"
    echo
); done