ps的Java exec会产生意想不到的结果

Question

我想从Java内部检测另一个进程是否正在执行。

unsafe bool ArePixelsEqual(byte* p1, byte* p2, int bytesPerPixel)
{
    for (int i = 0; i < bytesPerPixel; ++i)
        if (p1[i] != p2[i])
            return false;
    return true;
}

private static unsafe List<Rectangle> CodeImage(Bitmap bmp, Bitmap bmp2)
{
    if (bmp.PixelFormat != bmp2.PixelFormat || bmp.Width != bmp2.Width || bmp.Height != bmp2.Height)
        throw new ArgumentException();

    List<Rectangle> rec = new List<Rectangle>();
    var bmData1 = bmp.LockBits(new System.Drawing.Rectangle(0, 0, bmp.Width, bmp.Height), System.Drawing.Imaging.ImageLockMode.ReadOnly, bmp.PixelFormat);
    var bmData2 = bmp2.LockBits(new System.Drawing.Rectangle(0, 0, bmp.Width, bmp.Height), System.Drawing.Imaging.ImageLockMode.ReadOnly, bmp2.PixelFormat);

    int bytesPerPixel = Image.GetPixelFormatSize(bmp.PixelFormat) / 8;        

    IntPtr scan01 = bmData1.Scan0;
    IntPtr scan02 = bmData2.Scan0;
    int stride1 = bmData1.Stride;
    int stride2 = bmData2.Stride;
    int nWidth = bmp.Width;
    int nHeight = bmp.Height;

    bool[] visited = new bool[nWidth * nHeight];

    byte* base1 = (byte*)scan01.ToPointer();
    byte* base2 = (byte*)scan02.ToPointer();

        for (int y = 0; y < nHeight; y++)
        {
            byte* p1 = base1;
            byte* p2 = base2;

            for (int x = 0; x < nWidth; ++x)
            {
                if (!ArePixelsEqual(p1, p2, bytesPerPixel) && !(visited[x + nWidth * y]))
                {
                    // fill the different area
                    int minX = x;
                    int maxX = x;
                    int minY = y;
                    int maxY = y;

                    var pt = new Point(x, y);

                    Stack<Point> toBeProcessed = new Stack<Point>();
                    visited[x + nWidth * y] = true;
                    toBeProcessed.Push(pt);
                    while (toBeProcessed.Count > 0)
                    {
                        var process = toBeProcessed.Pop();
                        var ptr1 = (byte*)scan01.ToPointer() + process.Y * stride1 + process.X * bytesPerPixel;
                        var ptr2 = (byte*)scan02.ToPointer() + process.Y * stride2 + process.X * bytesPerPixel;
                        //Check pixel equality
                        if (ArePixelsEqual(ptr1, ptr2, bytesPerPixel))
                            continue;

                        //This pixel is different
                        //Update the rectangle
                        if (process.X < minX) minX = process.X;
                        if (process.X > maxX) maxX = process.X;
                        if (process.Y < minY) minY = process.Y;
                        if (process.Y > maxY) maxY = process.Y;

                        Point n; int idx;
                        //Put neighbors in stack
                        if (process.X - 1 >= 0)
                        {
                            n = new Point(process.X - 1, process.Y); idx = n.X + nWidth * n.Y;
                            if (!visited[idx]) { visited[idx] = true; toBeProcessed.Push(n); }
                        }

                        if (process.X + 1 < nWidth)
                        {
                            n = new Point(process.X + 1, process.Y); idx = n.X + nWidth * n.Y;
                            if (!visited[idx]) { visited[idx] = true; toBeProcessed.Push(n); }
                        }

                        if (process.Y - 1 >= 0)
                        {
                            n = new Point(process.X, process.Y - 1); idx = n.X + nWidth * n.Y;
                            if (!visited[idx]) { visited[idx] = true; toBeProcessed.Push(n); }
                        }

                        if (process.Y + 1 < nHeight)
                        {
                            n = new Point(process.X, process.Y + 1); idx = n.X + nWidth * n.Y;
                            if (!visited[idx]) { visited[idx] = true; toBeProcessed.Push(n); }
                        }
                    }

                    rec.Add(new Rectangle(minX, minY, maxX - minX + 1, maxY - minY + 1));
                }

                p1 += bytesPerPixel;
                p2 += bytesPerPixel;
            }

            base1 += stride1;
            base2 += stride2;
        }


    bmp.UnlockBits(bmData1);
    bmp2.UnlockBits(bmData2);

    return rec;
}

你会期望“ps -efl”产生几十行输出，至少。相反，我只得到：

PID TTY TIME CMD

21025 pts / 1 00:00:00 bash

22133 pts / 1 00:00:04 java

22169 pts / 1 00:00:00 ps

即。进程ID。 “ps”本身，运行它的Java会话，以及运行Java的bash shell。

顺便说一句，执行“bash -c'ps -efl'”，无论是否带有单引号，都不会产生输出。

知道如何列出直接进程及其父进程之外的进程吗？