bootstrap/specs/postgres/runner

#!/usr/bin/env bash

# Exit immediately if the script encounters a non-zero status.
set -e

# If set, Bash includes filenames beginning with a `.` in the results of
# filename expansion. The filenames `.` and `..` must always be matched
# explicitly, even if dotglob is set.
shopt -s dotglob

# ============================================================
# PROLOGUE
# ============================================================

# Create a new top-level directory as fallback in case $BUILD (defined below)
# is ever empty.
mkdir -p "/tmp/bs.postgres"

# Create an intermediate build directory. The final step of this script will
# copy the content from this directory to $OUT.
BUILD=$(mktemp -d -p "/tmp/bs.postgres")

if [ -z "$BUILD" ]; then
  >&2 echo "Failed to create temp directory."
  exit 1
fi

# Deletes the intermediate build directory on exit. We use a concatenation of
# the intermediate directory with the basename of the generated temp directory
# to ensure we never evaluate to root (i.e. `/`). That should never actually
# happen but a good habit to establish nonetheless.
function cleanup {
  rm -r "/tmp/bs.postgres/$(basename "$BUILD")"
}

trap cleanup EXIT

# ============================================================
# BUILD
# ============================================================

# Copy template contents over to the intermediate build directory.
cp -r template/* "$BUILD"

# Create a new database cluster.
nix develop "$BUILD" --command bash -c "pg_ctl initdb -D $BUILD/db"

# Explicitly set permissions on all copied files.
find "$BUILD" -type f -execdir chmod 644 {} +

# ============================================================
# EPILOGUE
# ============================================================

# Success! Copy contents to target directory.
cp -r "$BUILD"/* "$OUT"