sanitize-variables.bash

#!/usr/bin/env bash

# Reads lines from stdin in the format `VAR=value` and escapes
# them for the shell, prepending each line with `export`.
# Parameter substitution is allowed in `value` with `$VAR` and
# `${VAR}` syntax. You can escape `$` and `\` with a backslash.

sed \
  -e "/^[ "$'\t'"]*[A-Za-z_][0-9A-Za-z_]*=/ !d" \
  -e "s/'/'\\\\''/g" \
  -e "s/\(\\\\\\\$\)/'\\1'/g" \
  -e "s/\\\\\\\\/\\\\/g" \
  -e "s/\(\\\$[0-9A-Za-z_][0-9A-Za-z_]*\)/'\\1'/g" \
  -e "s/\(\\\${[0-9A-Za-z_][0-9A-Za-z_]*}\)/'\\1'/g" \
  -e "s/^[ "$'\t'"]*\([A-Za-z_][0-9A-Za-z_]*\)=\(.*\)$/export \\1='\\2'/"

Obviously.