diff --git a/local/dfm/dfm b/local/dfm/dfm
index fb49729..2298a54 100755
--- a/local/dfm/dfm
+++ b/local/dfm/dfm
@@ -6,8 +6,11 @@ set -euo pipefail
 # define default variables
 DFM_SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 readonly DFM_SCRIPT_DIR
+export DFM_SCRIPT_DIR
 readonly DFM_CMD_DIR="${DFM_SCRIPT_DIR}/cmd"
+export DFM_CMD_DIR
 readonly DFM_LIB_DIR="${DFM_SCRIPT_DIR}/lib"
+export DFM_LIB_DIR
 readonly DFM_DEFAULT_CONFIG_PATH="$HOME/.config"
 export DFM_DEFAULT_CONFIG_PATH
 readonly DFM_MAX_RETRIES=3
@@ -17,10 +20,43 @@ export DFM_DEFAULT_VERBOSE=0
 TEMP_DIR=$(mktemp -d)
 export TEMP_DIR
 
+# Clean up temporary directory on exit
+trap 'rm -rf "$TEMP_DIR"' EXIT
+
 # Load the common and utility functions from the lib directory.
+[[ -f "${DFM_LIB_DIR}/common.sh" ]] || {
+  echo "Error: Required file ${DFM_LIB_DIR}/common.sh not found"
+  exit 1
+}
+[[ -f "${DFM_LIB_DIR}/utils.sh" ]] || {
+  echo "Error: Required file ${DFM_LIB_DIR}/utils.sh not found"
+  exit 1
+}
 source "${DFM_LIB_DIR}/common.sh"
 source "${DFM_LIB_DIR}/utils.sh"
 
+# Display help information
+#
+# @return None
+main::show_help()
+{
+  cat << EOF
+Usage: dfm [command] [function] [arguments]
+
+dotfiles manager utility for installing and configuring dotfiles.
+
+If no arguments are provided, lists all available commands.
+If only a command is provided, lists available functions for that command.
+If a command and function are provided, executes the specified function.
+
+Examples:
+  dfm                    # List all available commands
+  dfm install            # List available functions for the install command
+  dfm install all        # Execute the 'all' function from the install command
+
+EOF
+}
+
 # Main function for the dfm script.
 #
 # The function checks if any arguments were provided. If no arguments are
@@ -40,6 +76,11 @@ main()
   local cmd="$1"
   shift
 
+  if [[ "$cmd" == "-h" || "$cmd" == "--help" ]]; then
+    main::show_help
+    return 0
+  fi
+
   if [[ $# -eq 0 ]]; then
     # Show the available functions for the command
     local cmd_file="${DFM_CMD_DIR}/${cmd}.sh"
diff --git a/local/dfm/lib/utils.sh b/local/dfm/lib/utils.sh
index e82cd37..1894b4f 100755
--- a/local/dfm/lib/utils.sh
+++ b/local/dfm/lib/utils.sh
@@ -109,6 +109,7 @@ list::print_subcommand()
 
 list::loop_functions()
 {
+  local cmd_file="$1"
   while IFS= read -r func; do
     # Get the function description from the function definition in the
     # command file. If no description is found, print only the function name.
@@ -282,7 +283,7 @@ main::find_commands()
   local cmd_files=()
   while IFS= read -r -d '' file; do
     cmd_files+=("$file")
-  done < <(find "$CMD_DIR" -type f -name "*.sh" -print0)
+  done < <(find "$DFM_CMD_DIR" -type f -name "*.sh" -print0)
   echo "${cmd_files[@]}"
 }
 
@@ -297,7 +298,7 @@ main::find_commands()
 main::get_command_functions()
 {
   local cmd_file="$1"
-  # Etsitään funktiomäärittelyt (function xxx() tai xxx())
+  # Find function definitions (function xxx() or xxx())
   grep -E '^[[:space:]]*(function[[:space:]]+)?[a-zA-Z0-9_]+\(\)[[:space:]]*{' "$cmd_file" \
     | sed -E 's/^[[:space:]]*(function[[:space:]]+)?([a-zA-Z0-9_]+).*/\2/'
 }
@@ -360,12 +361,24 @@ main::execute_command()
   local func="$1"
   shift
 
-  local cmd_file="${CMD_DIR}/${cmd}.sh"
-  if [[ ! -f "$cmd_file" ]]; then
+  # Validate input
+  if [[ ! "$cmd" =~ ^[a-zA-Z0-9_-]+$ ]] || [[ ! "$func" =~ ^[a-zA-Z0-9_-]+$ ]]; then
+    lib::error "Invalid command or function name"
+    return 1
+  fi
+
+  local cmd_file="${DFM_CMD_DIR}/${cmd}.sh"
+  if [[ ! -f "$cmd_file" ]] || [[ ! -r "$cmd_file" ]]; then
     lib::error "Command '$cmd' not found"
     return 1
   fi
 
+  # Validate command file
+  if ! bash -n "$cmd_file"; then
+    lib::error "Command file '$cmd' contains syntax errors"
+    return 1
+  fi
+
   # Source the command file
   # shellcheck source=/dev/null
   source "$cmd_file"