Erlang 备忘清单 === [Erlang](https://www.erlang.org/) 是一种用于构建并发、分布式和容错系统的编程语言。以下是一些常用的命令和操作。 入门 --- ### 启动 Erlang Shell ```shell erl ``` ### 编译代码 ```shell # 在 Erlang Shell 中编译 c(module). # 在命令行中编译 erlc module.erl ``` ### 运行代码 ```shell # 在 Erlang Shell 中运行 module:function(). # 从命令行运行 erl -noshell -s module function -s init stop ``` ### 退出 Erlang Shell ```shell q(). ``` 代码结构 --- ### 模块定义 ```erlang -module(module_name). -export([function_name/arity, ...]). function_name(Args) -> % Function body. Result. ``` ### 导出函数 ```erlang -export([function1/0, function2/1]). ``` ### 注释 ```erlang % 单行注释 % 这是一个注释 ``` ### 变量 ```erlang VarName = Value. % 变量名必须以大写字母开头 Age = 25. Name = "Alice". ``` 数据类型 --- ### 原子 ```erlang atom. % 例子：atom, 'Atom with spaces' ``` ### 数字 ```erlang 123. % 整数 3.14. % 浮点数 ``` ### 布尔值 ```erlang true. false. ``` ### 字符串 ```erlang "Hello, World!". ``` ### 元组 ```erlang {ok, "Success"}. ``` ### 列表 ```erlang [1, 2, 3]. [H|T] = [1, 2, 3]. % H = 1, T = [2, 3] ``` ### 字典 (Map) ```erlang #{key1 => value1, key2 => value2}. ``` 控制结构 --- ### 条件语句 ```erlang if Condition1 -> Expression1; Condition2 -> Expression2; true -> DefaultExpression end. ``` ### case 表达式 ```erlang case Expression of Pattern1 -> Expression1; Pattern2 -> Expression2; _ -> DefaultExpression end. ``` ### 函数定义 ```erlang % 无参函数 my_function() -> ok. % 有参函数 add(A, B) -> A + B. ``` 列表操作 --- ### 列表生成 ```erlang % 生成 1 到 10 的列表 [ X || X <- lists:seq(1, 10)]. % 生成 1 到 10 中的偶数 [ X || X <- lists:seq(1, 10), X rem 2 == 0]. ``` 并发 --- ### 启动进程 ```erlang spawn(Module, Function, Args). % 示例 Pid = spawn(fun() -> io:format("Hello from process~n") end). ``` ### 发送消息 ```erlang Pid ! Message. % 示例 Pid ! {hello, self()}. ``` ### 接收消息 ```erlang receive Pattern1 -> Expression1; Pattern2 -> Expression2; after Timeout -> TimeoutExpression end. ``` ### 模式匹配 ```erlang {ok, Value} = {ok, 42}. ``` 常用内置函数 (BIFs) --- ### 列表操作 ```erlang lists:append(List1, List2). lists:map(Function, List). lists:filter(Function, List). lists:foldl(Function, Acc, List). ``` ### 元组操作 ```erlang element(N, Tuple). setelement(N, Tuple, Value). tuple_size(Tuple). ``` ### 字符串操作 ```erlang string:len(String). string:concat(String1, String2). string:tokens(String, Delimiters). ``` ### 文件操作 ```erlang file:read_file(Filename). file:write_file(Filename, Data). file:delete(Filename). ``` ### 列表操作 ```erlang lists:map(fun(X) -> X * 2 end, [1, 2, 3]). lists:filter(fun(X) -> X rem 2 == 0 end, [1, 2, 3, 4]). ``` ### 字符串操作 ```erlang string:len("Hello"). string:upper("hello"). ``` ### 文件操作 ```erlang {ok, File} = file:open("test.txt", [write]). file:write(File, "Hello, file!"). file:close(File). ``` ### 示例：简单的服务器 ```erlang -module(server). -export([start/0, loop/0]). start() -> spawn(fun loop/0). loop() -> receive {echo, Msg} -> io:format("Echo: ~p~n", [Msg]), loop(); stop -> io:format("Server stopping~n"), ok; _ -> io:format("Unknown message~n"), loop() end. ``` 并发编程 --- ### 创建进程 ```erlang Pid = spawn(Module, Function, Args). ``` ### 发送消息 ```erlang Pid ! Message. ``` ### 接收消息 ```erlang receive Pattern1 -> Actions1; Pattern2 -> Actions2; ... end. ``` ### 链接进程 ```erlang link(Pid). unlink(Pid). ``` ### 监控进程 ```erlang MonitorRef = erlang:monitor(process, Pid). erlang:demonitor(MonitorRef). ``` 错误处理 --- ### 捕获异常 ```erlang try Expression of Pattern -> Result catch Class:Reason -> Handler end. ``` ### 常见异常类型 - `throw` - `error` - `exit` ### 错误处理 ```erlang try Expression of Pattern -> Result catch Type:Reason -> ErrorHandlingExpression end. ``` 分布式编程 --- ### 启动分布式节点 ```shell erl -name nodename@hostname -setcookie Cookie ``` ### 连接节点 ```erlang net_adm:ping(Node). ``` ### 发送消息到远程节点 ```erlang {remote_process, 'remote_node@host'} ! Message. ``` OTP 框架 --- ### 定义 GenServer ```erlang -module(my_gen_server). -behaviour(gen_server). -export([start_link/0, init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2, code_change/3]). start_link() -> gen_server:start_link({local, ?MODULE}, ?MODULE, [], []). init([]) -> {ok, #state{}}. handle_call(Request, From, State) -> {reply, Reply, State}. handle_cast(Msg, State) -> {noreply, State}. handle_info(Info, State) -> {noreply, State}. terminate(Reason, State) -> ok. code_change(OldVsn, State, Extra) -> {ok, State}. ``` ### 使用 GenServer ```erlang gen_server:start_link({local, Name}, Module, Args, Options). gen_server:call(ServerRef, Request). gen_server:cast(ServerRef, Msg). ``` 测试 --- ### 编写 EUnit 测试 ```erlang -module(module_name_tests). -include_lib("eunit/include/eunit.hrl"). simple_test() -> ?assertEqual(Expected, Actual). complex_test_() -> [ {"Test case 1", ?_assertEqual(Expected1, Actual1)}, {"Test case 2", ?_assertEqual(Expected2, Actual2)} ]. ``` ### 运行 EUnit 测试 ```shell # 在命令行中运行 erl -eval "eunit:test(module_name)" -s init stop ``` 另见 --- - [Erlang 官方文档](https://www.erlang.org/docs) - [Erlang 编程书籍](https://learnyousomeerlang.com/content)