c++ - ndk开发 popen函数替代

Question

ndk开发中需要用到 命令获取一些参数信息，目前知道的是有两种方法

1. popen

2. system

popen发现在小米商店上不了架，但是system在Android下无法写入文件。
比如'ps > /sdcard/.log' 运行后可以发现'.log'文件已经创建 但是文件内并没有任务信息。

具体代码：

    FILE *fp;
    char cmd[MAX];
    char dir_path[MAX];
    sprintf(dir_path, "/sdcard/.log");
    sprintf(cmd, "ps > %s", dir_path);
    int status;
    sighandler_t old_handler;
    old_handler = signal(SIGCHLD, SIG_DFL);
    status = system(cmd);
    signal(SIGCHLD, old_handler);
    if(status < 0){
        DEBUG_PRINT("cmd: %s\t error: %s", cmd, strerror(errno));
    }
    fp = fopen(dir_path, "r");
    if (fp) {
        while (fgets(line, MAX, fp)) {
            process_count ++;
            DEBUG_PRINT("msg:%s, len:%d", line, strlen(line));
        }
    }
    fclose(fp);

Answer 1

Whether it is popen or system, it can be both fork and exec....

Answer 2

I think it’s not because it uses popen, a function in <stdio.h>, that it can’t be put on the shelves.
Android apps like KSWeb that integrate Nginx/PHP/MySQL can’t be put on the Google Store.
Java's Runtime.getRuntime().exec() is essentially a fork process.
The zygote process zygote run by Android's root user is also essentially a fork.
Could it be that the process cannot be launched because it is forked? I think it’s impossible.
Isn’t there any feedback when the Xiaomi Mi Store app is removed?

The bottom layer of popen in GNU libc is execve in Unix Standard Header (unistd.h).