如何將終端的命令輸出和退出代碼存盤在變數中

從這里我得到了給我命令列輸出和退出代碼的代碼。不幸的是，我不太了解該運算子多載，如果我嘗試將其重寫為我知道的簡單代碼（使用全域變數，即），我總是得到錯誤的退出代碼狀態 0。

那么如何修改以下代碼，以便存盤輸出和退出代碼狀態以供將來使用？

#include <cstdio>
#include <iostream>
#include <memory>
#include <stdexcept>
#include <string>
#include <array>


struct CommandResult {
    std::string output;
    int exitstatus;

    friend std::ostream &operator<<(std::ostream &os, const CommandResult &result) {
        os << "command exitstatus: " << result.exitstatus << " output: " << result.output;
        return os;
    }
    bool operator==(const CommandResult &rhs) const {
        return output == rhs.output &&
               exitstatus == rhs.exitstatus;
    }
    bool operator!=(const CommandResult &rhs) const {
        return !(rhs == *this);
    }
};


class Command {

public:
    /**
     * Execute system command and get STDOUT result.
     * Like system() but gives back exit status and stdout.
     * @param command system command to execute
     * @return CommandResult containing STDOUT (not stderr) output & exitstatus
     * of command. Empty if command failed (or has no output). If you want stderr,
     * use shell redirection (2&>1).
     */
    static CommandResult exec(const std::string &command) {
        int exitcode = 255;
        std::array<char, 1048576> buffer {};
        std::string result;
#ifdef _WIN32
#define popen _popen
#define pclose _pclose
#define WEXITSTATUS
#endif
        FILE *pipe = popen(command.c_str(), "r");
        if (pipe == nullptr) {
            throw std::runtime_error("popen() failed!");
        }
        try {
            std::size_t bytesread;
            while ((bytesread = fread(buffer.data(), sizeof(buffer.at(0)), sizeof(buffer), pipe)) != 0) {
                result  = std::string(buffer.data(), bytesread);
            }
        } catch (...) {
            pclose(pipe);
            throw;
        }
        exitcode = WEXITSTATUS(pclose(pipe));
        return CommandResult{result, exitcode};
    }
};

int main ()
{
    std::cout << Command::exec("echo blablub") << std::endl;
}

這是我的代碼，函式中的全域變數是正確的，但之后會被覆寫。

#include <cstdio>
#include <iostream>
#include <memory>
#include <stdexcept>
#include <string>
#include <array>

int exitcode = 555;

std::string exec(const std::string cmd) {
    
    int exitcode = 255;
    std::array<char, 128> buffer {};
    std::string result;
    
    
    #ifdef _WIN32
    #define popen _popen
    #define pclose _pclose
    #define WEXITSTATUS
    #endif
    
    
    FILE *pipe = popen(cmd.c_str(), "r");
    if (pipe == nullptr) {
        throw std::runtime_error("popen() failed!");
    }
    try {
        std::size_t bytesread;
        while ((bytesread = fread(buffer.data(), sizeof(buffer.at(0)), sizeof(buffer), pipe)) != 0) {
            result  = std::string(buffer.data(), bytesread);
        }
    } catch (...) {
        pclose(pipe);
        throw;
    }    
    
    exitcode = WEXITSTATUS(pclose(pipe));
    std::cout<<exitcode<<'\n';
    return result;
}



int main (){
    exec("echo bla");
    std::cout<<exitcode<<'\n';
}

uj5u.com熱心網友回復：

假設文章中提供的代碼是正確的并且做了它應該做的，它已經做了你需要的一切。退出代碼和輸出從exec函式回傳。

您只需使用回傳的CommandResult并訪問其成員：

int main() {
   auto result = Command::exec("echo blablub");
   std::cout << result.output << "\n":
   std::cout << result.exitstatus << "\n";
}

標籤：C c 11 运算符重载 返回值

上一篇：關于std::istream&運算子實作的問題>>(std::istream&is,icmp_header&header)

下一篇：`std::cout`和`std::ostream`之間有什么關系？