在文件上使用mmap(Using mmap over a file)

 我试图让两个不同的进程通过使用内存映射相同的文件进行通信。 不过，我在这方面遇到了一些问题。 我有一种感觉，这与我使用open（）调用并将文件描述符传递给mmap的方式有关。 
 
 这是我的代码，你能看到它有什么问题吗？ 
 
 对象1的代码： 
 
 16     FILE* temp = fopen(theSharedFileName, "w");
 17     fseek(temp, fileSize-1, SEEK_SET);
 18     fprintf(temp, "0"); // make the file a certain size
 19     fseek(temp, 0, SEEK_CUR);
 20 
 21     int sharedFileName = fileno(temp);
 ...
 31     sharedArea = (MyStruct*)mmap(0, fileSize,
 32         PROT_READ | PROT_WRITE | PROT_EXEC, MAP_SHARED, sharedFileName, 0);
 
 我使用“w”文件模式，因为对象1只能制作一次，我希望它重置以前存在的任何数据。 
 
 对象2的代码： 
 
 130     FILE* tempFile = fopen(sharedFileName, "a");
 131     int theFile = fileno(tempFile);
 ...
 135     sharedArea = (MyStruct*)mmap(NULL, fileSize,
 136         PROT_READ | PROT_WRITE | PROT_EXEC, MAP_SHARED, theFile, 0);

I'm trying to allow two different processes to communicate by using memory mapping the same file. However, I'm having some problems with this. I have a feeling this has to do with the way I'm using the open() call and passing my file descriptor to mmap. 
 
Here is my code, can you see anything wrong with it?
 
Object 1's code:
 
 16     FILE* temp = fopen(theSharedFileName, "w");
 17     fseek(temp, fileSize-1, SEEK_SET);
 18     fprintf(temp, "0"); // make the file a certain size
 19     fseek(temp, 0, SEEK_CUR);
 20 
 21     int sharedFileName = fileno(temp);
 ...
 31     sharedArea = (MyStruct*)mmap(0, fileSize,
 32         PROT_READ | PROT_WRITE | PROT_EXEC, MAP_SHARED, sharedFileName, 0);
 
I use the "w" file mode since Object 1 will only ever be made once and I want it to reset any previously existing data.
 
Object 2's Code:
 
 130     FILE* tempFile = fopen(sharedFileName, "a");
 131     int theFile = fileno(tempFile);
 ...
 135     sharedArea = (MyStruct*)mmap(NULL, fileSize,
 136         PROT_READ | PROT_WRITE | PROT_EXEC, MAP_SHARED, theFile, 0);

原文：https://stackoverflow.com/questions/742564