妥善处理 std.getopt.GetOptException

Question

如何正确处理缺少必需的命令行参数时抛出的 std.getopt.GetOptException 异常。

声明需要的参数会引发以下错误，方式过于冗长：

std.getopt.GetOptException@/Library/D/dmd/src/phobos/std/getopt.d(755): Required option file|f was not supplied
----------------
/Library/D/dmd/src/phobos/std/format.d-mixin-1127:1138 @safe std.getopt.GetoptResult std.getopt.getopt!(std.getopt.config, immutable(char)[], immutable(char)[], immutable(char)[]*, std.getopt.config, immutable(char)[], immutable(char)[], immutable(char)[]*, immutable(char)[], immutable(char)[], bool*, immutable(char)[], immutable(char)[], bool*).getopt(ref immutable(char)[][], std.getopt.config, immutable(char)[], immutable(char)[], immutable(char)[]*, std.getopt.config, immutable(char)[], immutable(char)[], immutable(char)[]*, immutable(char)[], immutable(char)[], bool*, immutable(char)[], immutable(char)[], bool*) [0xbb5a9d1]
source/app.d:11 _Dmain [0xbb58996]
std.getopt.GetOptException@/Library/D/dmd/src/phobos/std/getopt.d(755): Required option key|k was not supplied

使用以下代码重现：

import std.stdio;
import std.getopt;

int main(string[] args)
{
    string key;
    string inputFile;
    bool encrypt;
    bool decrypt;

    auto result = getopt(
        args,
        std.getopt.config.required,
        "key|k", "The key to use", &key,
        std.getopt.config.required,
        "file|f", "The file to encrypt/decrypt", &inputFile,
        "encrypt|e", "Encrypt the file", &encrypt,
        "decrypt|d", "Decrypt the file", &decrypt
    );

    if (result.helpWanted) {
        defaultGetoptPrinter("Some information about the program.", result.options);
    }

    return 0;
}

Answer 1

一个合理的方法是将 getopt 调用包装在 try-catch 块中，捕获任何错误，并在退出前仅写入错误消息部分。这将避免写入堆栈跟踪，这对大多数用户没有帮助。修改上面的例子：

import std.stdio;
import std.getopt;

int main(string[] args)
{
    string key;
    string inputFile;
    bool encrypt;
    bool decrypt;

    try {
        auto result = getopt(
            args,
            std.getopt.config.required,
            "key|k", "The key to use", &key,
            std.getopt.config.required,
            "file|f", "The file to encrypt/decrypt", &inputFile,
            "encrypt|e", "Encrypt the file", &encrypt,
            "decrypt|d", "Decrypt the file", &decrypt
        );

        if (result.helpWanted) {
            defaultGetoptPrinter("Some information about the program.", result.options);
        }
    }
    catch (Exception e) {
        stderr.writefln("Error processing command line arguments: %s", e.msg);
        return 1;
    }

    return 0;
}

运行时的错误信息：

Error processing command line arguments: Required option file|f was not supplied

D 语言 'Learn' 论坛上有一个与此相关的帖子可能有用：What's the proper way to use std.getopt?. I've written some open source command line tools that are a bit more extensive examples, eg. tsv-sample.d。

妥善处理 std.getopt.GetOptException

Proper handling of std.getopt.GetOptException

command-line

d

command-line-arguments