pyenv plugin to scan for dependent virtual environments

pyenv-users

#!/usr/bin/env bash
#
# Summary: Find virtual environments that use pyenv-managed versions.
#
# Usage: pyenv users [directory]
#
# Scans [directory] for virtual environments whose `python` commands
# are symlinks back into a pyenv version. Default: current directory.
#
# I'm not a script writer so it's probably a bit crude, but I find it
# helpful for checking if I can uninstall old Python versions. Uses
# the `column` command from the util-linux package (if available) for
# pretty-printing the output.

if [ -n "$1" ]; then
  DIR="$1"
else
  DIR="$PYENV_DIR"
fi

cmd="readlink -f '{}' | grep -q ${PYENV_ROOT}"
unset links i
while IFS= read -r -d $'\0' file; do
  links[i++]="$file"
done < <(find -H "$DIR" -name "python" -type l -exec sh -c "$cmd" \; -print0)

# Exit if no relevant venvs were found
if [[ $i -eq 0 ]]; then
  exit 0
fi

# Use columnar output if convenient.
if [ -n "$(command -v column)" ]; then
  output="column -t -s ':'"
else
  output="cat"
fi

# Regex to extract the pyenv version from the target string. The
# second group consumes the actual binary (`python`, `pypy3`, etc)
regex="${PYENV_ROOT}/versions/(.+)/bin/(.+)"

for link in "${links[@]}"; do
  # `$link` is the `python` symlink, and `$target` is its target.
  target=$(readlink -f "$link")
  # Ignore symlinks inside $PYENV_ROOT itself
  if realpath -s "$link" | grep -v -q "$PYENV_ROOT"; then
    [[ "$target" =~ $regex ]]
    version="${BASH_REMATCH[1]}"
    echo "$version":"${link%/bin/python}"
  fi
done | sort | $output