#!/bin/bash

set -euo pipefail

usage() {
  echo "Usage: $0 [--prefix {prefix directory}], e.g. /usr/local" 2>&1
  echo "    or $0 [--prefix={prefix directory}], e.g. /usr/local" 2>&1
  exit 1
}

prefix="/usr/local"

if [ $# -eq 0 ]; then
  echo "Using $prefix"
elif [ $# -gt 2 ]; then
  usage
else
  while [ $# -gt 0 ]; do
    case "$1" in
      -p=* | --prefix=*)
        prefix="${1#*=}"
        ;;
      -p | --prefix)
        prefix="$2"
        shift
        ;;
      *)
        printf "Error: unknown option: $1\n"
        usage
    esac
    shift
  done
fi

# Test for read access, not write access, since people can ./configure, make,
# and make check outside of sudo and then make install inside sudo.
if [ ! -d "$prefix" ]; then
  echo "$0: could not find prefix directory \"$prefix\""
  exit 1
fi

ext=".prefix-backup"
sed 's@^PREFIX.*@PREFIX='$prefix'@' Makefile > Makefile.$ext
mv Makefile.$ext Makefile
echo Updated Makefile

sed 's@^PREFIX.*@PREFIX='$prefix'@' man/Makefile > man/Makefile.$ext
mv man/Makefile.$ext man/Makefile
echo Updated man/Makefile

