diff --git a/Dockerfile b/Dockerfile
index 2f5b7a9..8a201c4 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,5 +1,5 @@
 ARG ALPINE_VERSION=latest
-FROM alpine:${ALPINE_VERSION} as build
+FROM alpine:${ALPINE_VERSION} AS build
 
 ENV CXXFLAGS=""
 WORKDIR /usr/src/telegram-bot-api
diff --git a/docker-entrypoint.sh b/docker-entrypoint.sh
old mode 100644
new mode 100755
index 9817963..cb430ad
--- a/docker-entrypoint.sh
+++ b/docker-entrypoint.sh
@@ -1,87 +1,113 @@
-#!/bin/sh
+#!/usr/bin/env sh
 set -e
 
+USERNAME="telegram-bot-api"
+GROUPNAME="telegram-bot-api"
+
+COMMAND="telegram-bot-api"
+
+# Appends an argument to the COMMAND variable.
+append_args() {
+  COMMAND="$COMMAND $1"
+}
+
+# Sets $env_var from $file_env_var content or directly from $env_var.
+# Usage: file_env <env_var> <file_env_var>
+# - If both or neither variables are set, exits with an error.
+# - If only $file_env_var is set, reads content from the file path and sets $env_var.
+# - Exits with an error if the file does not exist.
 file_env() {
-  local var_name="$1"
-  local file_var_name="$2"
+    env_var="$1"
+    file_env_var="$2"
+    env_value=$(printenv "$env_var") || env_value=""
+    file_path=$(printenv "$file_env_var") || file_path=""
 
-  var_value=$(printenv "$var_name") || var_value=""
-  file_path=$(printenv "$file_var_name") || file_path=""
-
-  if [ -z "$var_value" ] && [ -z "$file_path" ]; then
-    echo "error: expected $var_name or $file_var_name env vars to be set"
-    exit 1
-
-  elif [ -n "$var_value" ] && [ -n "$file_path" ]; then
-    echo "both and $var_name $file_var_name env vars are set, expected only one of them"
-    exit 1
-
-  else
-    if [ -n "$file_path" ] && [ "$file_path" != "" ]; then
-      if [ -f "$file_path" ]; then
-        file_content=$(cat "$file_path")
-        export "$var_name=$file_content"
-      else
-        echo "error: $var_name=$file_path: file '$file_path' does not exist"
+    if [ -z "$env_value" ] && [ -z "$file_path" ]; then
+        echo "error: expected $env_var or $file_env_var env vars to be set"
         exit 1
-      fi
+    elif [ -n "$env_value" ] && [ -n "$file_path" ]; then
+        echo "both $env_var and $file_env_var env vars are set, expected only one of them"
+        exit 1
+    elif [ -n "$file_path" ]; then
+        if [ -f "$file_path" ]; then
+            export "$env_var=$(cat "$file_path")"
+        else
+            echo "error: $env_var=$file_path: file '$file_path' does not exist"
+            exit 1
+        fi
     fi
+}
+
+# Checks if an environment variable is set.
+# Usage: check_required_env <var_name>
+# - Exits with an error if the variable is not set.
+check_required_env() {
+  var_name="$1"
+
+  if [ -z "$(printenv "$var_name")" ]; then
+    echo "error: environment variable $var_name is required"
+    exit 1
   fi
 }
 
-USERNAME=telegram-bot-api
-GROUPNAME=telegram-bot-api
+# Appends an argument to CUSTOM_ARGS based on the environment variable value.
+# Usage: append_arg_from_env <var_name> <arg_name> <default_value>
+# - If <var_name> is set, uses its value; otherwise, uses <default_value>.
+# - Appends "<arg_name>=<value>" to CUSTOM_ARGS if a value is found.
+append_arg_from_env() {
+    var_name="$1"
+    arg_name="$2"
+    default_value="$3"
+    env_value=$(printenv "$var_name") || env_value=""
 
-chown ${USERNAME}:${GROUPNAME} "${TELEGRAM_WORK_DIR}"
+    [ -n "$env_value" ] || env_value="$default_value"
+    if [ -n "$env_value" ]; then
+      append_args "${arg_name}=$env_value"
+    fi
+}
 
-if [ -n "${1}" ]; then
-  exec "${*}"
-fi
+# Appends a flag to CUSTOM_ARGS if the environment variable is set (non-empty).
+# Usage: append_flag_from_env <var_name> <flag_name>
+# - If <var_name> is set, appends <flag_name> to CUSTOM_ARGS.
+append_flag_from_env() {
+  var_name="$1"
+  flag_name="$2"
 
+  if [ -n "$(printenv "$var_name")" ]; then
+    append_args "$flag_name"
+  fi
+}
+
+check_required_env "TELEGRAM_WORK_DIR"
+chown "${USERNAME}:${GROUPNAME}" "${TELEGRAM_WORK_DIR}"
+
+# Telegram Bot API Server knows how to read the API ID and API Hash from a environment variable.
+# Is not needed to pass it as arguments.
 file_env "TELEGRAM_API_ID" "TELEGRAM_API_ID_FILE"
 file_env "TELEGRAM_API_HASH" "TELEGRAM_API_HASH_FILE"
 
-DEFAULT_ARGS="--dir=${TELEGRAM_WORK_DIR} --temp-dir=${TELEGRAM_TEMP_DIR} --username=${USERNAME} --groupname=${GROUPNAME}"
-CUSTOM_ARGS=""
+# Default arguments, passed from the Dockerfile.
+# Potentially can be overwritten by environment variables, if needed, but is not recommended.
+append_arg_from_env "TELEGRAM_WORK_DIR" "--dir"
+check_required_env "TELEGRAM_TEMP_DIR"
+append_arg_from_env "TELEGRAM_TEMP_DIR" "--temp-dir"
+append_args "--username=${USERNAME}"
+append_args "--groupname=${GROUPNAME}"
 
-if [ -n "$TELEGRAM_LOG_FILE" ]; then
-  CUSTOM_ARGS=" --log=${TELEGRAM_LOG_FILE}"
-fi
-if [ -n "$TELEGRAM_STAT" ]; then
-  CUSTOM_ARGS="${CUSTOM_ARGS} --http-stat-port=8082"
-fi
-if [ -n "$TELEGRAM_FILTER" ]; then
-  CUSTOM_ARGS="${CUSTOM_ARGS} --filter=$TELEGRAM_FILTER"
-fi
-if [ -n "$TELEGRAM_MAX_WEBHOOK_CONNECTIONS" ]; then
-  CUSTOM_ARGS="${CUSTOM_ARGS} --max-webhook-connections=$TELEGRAM_MAX_WEBHOOK_CONNECTIONS"
-fi
-if [ -n "$TELEGRAM_VERBOSITY" ]; then
-  CUSTOM_ARGS="${CUSTOM_ARGS} --verbosity=$TELEGRAM_VERBOSITY"
-fi
-if [ -n "$TELEGRAM_MAX_CONNECTIONS" ]; then
-  CUSTOM_ARGS="${CUSTOM_ARGS} --max-connections=$TELEGRAM_MAX_CONNECTIONS"
-fi
-if [ -n "$TELEGRAM_PROXY" ]; then
-  CUSTOM_ARGS="${CUSTOM_ARGS} --proxy=$TELEGRAM_PROXY"
-fi
-if [ -n "$TELEGRAM_LOCAL" ]; then
-  CUSTOM_ARGS="${CUSTOM_ARGS} --local"
-fi
-if [ -n "$TELEGRAM_HTTP_IP_ADDRESS" ]; then
-  CUSTOM_ARGS="${CUSTOM_ARGS} --http-ip-address=$TELEGRAM_HTTP_IP_ADDRESS"
-fi
+check_required_env "TELEGRAM_API_ID"
+check_required_env "TELEGRAM_API_HASH"
 
-# Set http-port arg
-if [ -n "$TELEGRAM_HTTP_PORT" ]; then
-  CUSTOM_ARGS="${CUSTOM_ARGS} --http-port=$TELEGRAM_HTTP_PORT"
-else
-  CUSTOM_ARGS="${CUSTOM_ARGS} --http-port=8081"
-fi
-
-COMMAND="telegram-bot-api ${DEFAULT_ARGS}${CUSTOM_ARGS}"
+# Environment variables that can be passed as arguments from environment by administrator.
+append_arg_from_env "TELEGRAM_HTTP_PORT" "--http-port" "8081"
+append_flag_from_env "TELEGRAM_LOCAL" "--local"
+append_flag_from_env "TELEGRAM_STAT" "--http-stat-port=8082"  # maybe change it to dynamic variable in the future
+append_arg_from_env "TELEGRAM_LOG_FILE" "--log"
+append_arg_from_env "TELEGRAM_FILTER" "--filter"
+append_arg_from_env "TELEGRAM_MAX_WEBHOOK_CONNECTIONS" "--max-webhook-connections"
+append_arg_from_env "TELEGRAM_VERBOSITY" "--verbosity"
+append_arg_from_env "TELEGRAM_MAX_CONNECTIONS" "--max-connections"
+append_arg_from_env "TELEGRAM_PROXY" "--proxy"
+append_arg_from_env "TELEGRAM_HTTP_IP_ADDRESS" "--http-ip-address"
 
 echo "$COMMAND"
-
-# shellcheck disable=SC2086
 exec $COMMAND