Script to create gcroot directory for a devshell on nixos to make its packages persistent.

devshell_keep.sh

#!/usr/bin/env bash

# Define variables
store_dir="/nix/store"
gcroots_dir="/nix/var/nix/gcroots"

action="$1"
flake_dir="$2"
flake_path="$flake_dir/flake.nix"

# need to pass variable as string
# without $
is_empty() {
  local var_name="$1"
  local value="${!var_name}"
  if [ -z "$value" ]; then
    echo "The value of $var_name is empty"
  fi
}

is_dir() {
  # Check if the path is a directory
  local path=$1
  if [ ! -d "$path" ]; then
    echo "$path is not a directory."
    exit 1
  fi
}

check_path_exists() {
  local path=$1
  if [ ! -e "$path" ]; then
    echo "$path does not exist."
    exit 1
  fi
}

get_devshell_name() {
  local flake_path=$1
  local devShellLine
  local devShellName
  # if grep doesn't find anything, it will through error (exit 1)
  # to prevent it, using `true`
  devShellLine=$(grep name "$flake_path" || true)

  is_empty "devShellLine"
  # get only name in ""
  devShellName=$(echo "$devShellLine" | cut -d '"' -f2)

  is_empty "devShellName"
  echo "$devShellName"
  return 0
}

get_flake_source_path() {
  local flake_source_path
  flake_source_path=$(nix flake metadata | grep Path |  cut -d '/' -f 4)

  is_empty "flake_source_path"
  echo "$flake_source_path"
  return 0
}

# if there would be a error
# in the script
# it will exit automaticaly 
set -e

# Check if the path is provided
is_empty "flake_dir"
    
case "$action" in
  "clear")
    # Commands to execute if $variable matches pattern1
    # Check if the path exists
    check_path_exists "$flake_dir"
    # Check if the path is a directory
    is_dir "$flake_dir"
    # Check if the path exists
    check_path_exists "$flake_path"

    devShellName=$(get_devshell_name "$flake_path")
    devShellRootDir="$gcroots_dir/$devShellName"
    if [ ! -e "$devShellRootDir" ]; then
      echo "$devShellRootDir doesn't exists. Exiting..."
      exit 1
    fi
    sudo rm -rf "$devShellRootDir"
    echo "$devShellRootDir was deleted"
    exit 0
    ;;
  "pin")
    # Commands to execute if $variable matches pattern2
    # Check if the path exists
    check_path_exists "$flake_dir"
    # Check if the path is a directory
    is_dir "$flake_dir"
    # Check if the path exists
    check_path_exists "$flake_path"


    # if grep doesn't find anything, it will through error (exit 1)
    # to prevent it, using `true`
    devShellName=$(get_devshell_name "$flake_path")
    devShellRootDir="$gcroots_dir/$devShellName"

    # Check if the path does not exists
    if [ ! -e "$devShellRootDir" ]; then
      sudo mkdir "$devShellRootDir"
    fi

    file_paths=$(ls "$store_dir" | grep "$devShellName" || true)
    # filePaths are empty
    is_empty "file_paths"

    flake_source_path=$(get_flake_source_path)

    # append flake_source_path to the file_paths
    file_paths=$(echo "$file_paths"; echo "$flake_source_path")

    # Iterate over each derivative store path matching the devShell name
    for filePath in $file_paths; do
      # Define the symlink name and target
      storePath="$store_dir/$filePath"
      gcrootsDevShellPath="$devShellRootDir/$filePath"
      
      # Create the symlink if it does not already exist
      if [ ! -e "$gcrootsDevShellPath" ]; then
        sudo ln -s "$storePath" "$gcrootsDevShellPath"
        printf '✓Symlink was created\n%s\n↳%s\n\n' "$gcrootsDevShellPath" "$storePath"
      else
        printf '✖Symlink already exists\n%s\n\n' "$gcrootsDevShellPath"
      fi
    done


    echo "$devShellName is pinned in nix store!"
    notify-send -e "$devShellName is pinned in nix store!"
    exit 0
    ;;
  *)
    # Commands to execute if $action does not match any patterns
    echo "Only 'pin' and 'clear' actions are supported"
    exit 1
    ;;
esac