C++系統相關操作1 - 呼叫命令列並獲取返回值

• 1. 關鍵詞
• 2. sysutil.h
• 3. sysutil.cpp
  • 3.1. system_util_unix.cpp
  • 3.2. system_util_win.cpp
• 4. 測試程式碼
• 5. 執行結果
• 6. 原始碼地址

1. 關鍵詞

關鍵詞：

C++ 系統呼叫 system popen 跨平臺

應用場景：

希望直接呼叫作業系統的某些命令，並獲取命令的返回值。

2. sysutil.h

#pragma once

#include <cstdint>
#include <string>

namespace cutl
{
    /**
     * @brief Execute a system command.
     *
     * @param cmd the command to be executed.
     * @return true if the command is executed successfully, false otherwise.
     */
    bool system(const std::string &cmd);
    /**
     * @brief Execute a system command and get the output.
     *
     * @param cmd the command to be executed.
     * @param result the output of the command.
     * @return true if the command is executed successfully, false otherwise.
     */
    bool callcmd(const std::string &cmd, std::string &result);
} // namespace cutl

不需要返回值時，可以直接使用system， 需要獲取返回值時，可以呼叫callcmd。

3. sysutil.cpp

#include <map>
#include <iostream>
#include <strutil.h>
#include <cstdlib>
#include "sysutil.h"
#include "inner/logger.h"
#include "inner/system_util.h"
#include "inner/filesystem.h"

namespace cutl
{
    bool system(const std::string &cmd)
    {
        return call_system(cmd);
    }

    bool callcmd(const std::string &cmd, std::string &result)
    {
        // 讀取命令執行結果的最大Buffer長度
        constexpr int MAX_CMD_BUF_LEN = 1024;
        FILE *fp = pipline_open(cmd);
        if (fp == NULL)
        {
            CUTL_ERROR("pipline_open error for cmd:" + cmd);
            return false;
        }

        // 　讀取命令執行結果
        char buffer[MAX_CMD_BUF_LEN] = {0};
        char *res = fgets(buffer, sizeof(buffer), fp);
        if (res == NULL)
        {
            CUTL_ERROR("read result error for cmd:" + cmd);
            if (pipline_close(fp) != 0)
            {
                CUTL_ERROR("pipline_close error for cmd:" + cmd);
            }
            return false;
        }

        if (pipline_close(fp) != 0)
        {
            CUTL_ERROR("pipline_close error for cmd:" + cmd);
        }

        result = strip(std::string(buffer));

        return true;
    }
} // namespace cutl

3.1. system_util_unix.cpp

#if defined(_WIN32) || defined(__WIN32__)
// do nothing
#else

#include "system_util.h"
#include "inner/logger.h"

namespace cutl
{

    bool call_system(const std::string &cmd)
    {
        if (cmd.empty())
        {
            CUTL_ERROR("cmd is empty!");
            return false;
        }

        pid_t status;
        status = std::system(cmd.c_str());

        if (-1 == status)
        {
            CUTL_ERROR("system error!");
            return false;
        }

        if (!WIFEXITED(status))
        {
            CUTL_ERROR("exit status:" + std::to_string(WEXITSTATUS(status)));
            return false;
        }

        if (0 != WEXITSTATUS(status))
        {
            CUTL_ERROR("run shell script fail, script exit code:" + std::to_string(WEXITSTATUS(status)));
            return false;
        }

        return true;
    }

    FILE *pipline_open(const std::string &cmd)
    {
        return popen(cmd.c_str(), "r");
    }

    int pipline_close(FILE *stream)
    {
        return pclose(stream);
    }

} // namespace cutl

#endif // defined(_WIN32) || defined(__WIN32__)

3.2. system_util_win.cpp

#if defined(_WIN32) || defined(__WIN32__)

#include <cstdlib>
#include "system_util.h"
#include "inner/logger.h"

namespace cutl
{

    // https://learn.microsoft.com/zh-cn/cpp/c-runtime-library/reference/system-wsystem?view=msvc-170
    bool call_system(const std::string &cmd)
    {
        if (cmd.empty())
        {
            CUTL_ERROR("cmd is empty!");
            return false;
        }

        int ret = system(cmd.c_str());
        if (ret != 0)
        {
            CUTL_ERROR(std::string("system failure, error") + strerror(errno));
            return false;
        }

        return true;
    }

    // https://learn.microsoft.com/zh-cn/cpp/c-runtime-library/reference/popen-wpopen?view=msvc-170
    FILE *pipline_open(const std::string &cmd)
    {
        return _popen(cmd.c_str(), "r");
    }

    // https://learn.microsoft.com/zh-cn/cpp/c-runtime-library/reference/pclose?view=msvc-170
    int pipline_close(FILE *stream)
    {
        return _pclose(stream);
    }

} // namespace cutl

#endif // defined(_WIN32) || defined(__WIN32__)

4. 測試程式碼

#include "common.hpp"
#include "sysutil.h"

void TestSystemCall()
{
    PrintSubTitle("TestSystemCall");

    bool ret = cutl::system("echo hello");
    std::cout << "system call 'echo hello', return: " << ret << std::endl;

    auto cmd = "cmake --version";
    std::string result_text;
    ret = cutl::callcmd(cmd, result_text);
    std::cout << "callcmd " << cmd << ", return: " << ret << std::endl;
    std::cout << "callcmd " << cmd << ", result text: " << result_text << std::endl;
}

5. 執行結果

-------------------------------------------TestSystemCall-------------------------------------------
hello
system call 'echo hello', return: 1
callcmd cmake --version, return: 1
callcmd cmake --version, result text: cmake version 3.28.3

6. 原始碼地址

更多詳細程式碼，請檢視本人寫的C++ 通用工具庫: common_util, 本專案已開源，程式碼簡潔，且有詳細的文件和Demo。

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