如何获取用C ++中的system()命令执行的进程的pid [英] How to get pid of process executed with system() command in c++

问题描述

当我们使用system()命令时，程序要等到它完成为止，但是由于要在执行系统命令后立即进入下一行，因此我正在使用system()和负载平衡服务器来执行process.请注意，process可能不完整.

When we use system() command, program wait until it complete but I am executing a process using system() and using load balance server due to which program comes to next line just after executing system command. Please note that that process may not be complete.

system("./my_script");

// after this I want to see whether it is complete or not using its pid.
// But how do i Know PID?
IsScriptExecutionComplete();

推荐答案

简单的答案:不能.

system()的目的是在执行命令时阻塞.

The purpose of system() is to block when command is being executed.

但是您可以像这样作弊":

But you can 'cheat' like this:

pid_t system2(const char * command, int * infp, int * outfp)
{
    int p_stdin[2];
    int p_stdout[2];
    pid_t pid;

    if (pipe(p_stdin) == -1)
        return -1;

    if (pipe(p_stdout) == -1) {
        close(p_stdin[0]);
        close(p_stdin[1]);
        return -1;
    }

    pid = fork();

    if (pid < 0) {
        close(p_stdin[0]);
        close(p_stdin[1]);
        close(p_stdout[0]);
        close(p_stdout[1]);
        return pid;
    } else if (pid == 0) {
        close(p_stdin[1]);
        dup2(p_stdin[0], 0);
        close(p_stdout[0]);
        dup2(p_stdout[1], 1);
        dup2(::open("/dev/null", O_RDONLY), 2);
        /// Close all other descriptors for the safety sake.
        for (int i = 3; i < 4096; ++i)
            ::close(i);

        setsid();
        execl("/bin/sh", "sh", "-c", command, NULL);
        _exit(1);
    }

    close(p_stdin[0]);
    close(p_stdout[1]);

    if (infp == NULL) {
        close(p_stdin[1]);
    } else {
        *infp = p_stdin[1];
    }

    if (outfp == NULL) {
        close(p_stdout[0]);
    } else {
        *outfp = p_stdout[0];
    }

    return pid;
}

在这里，您不仅可以拥有该过程的 PID ，还可以具有 STDIN 和 STDOUT .玩得开心！

Here you can have not only PID of the process, but also it's STDIN and STDOUT. Have fun!

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