How can I create a file stream?

Question

File streams are always acceded through pointers and they are always pre-created. But is it possible to create a file stream inside the program as an object that holds space in memory without using an external file?

My first thought was to declare a FILE * pointer then allocate memory for a FILE object using malloc():

FILE *fileStream = malloc(sizeof(FILE));

but I guess this is not right.

How can I do it the right way so I can work with fileStream using the I/O functions like fprintf() and fscanf() ...

Do you mean you want to treat an in-memory buffer as a file? — Fred Foo, Jan 23 '14 at 12:35
I still don't understand what you mean. `stdin` is a vanilla `FILE*`. — Fred Foo, Jan 23 '14 at 12:38
@larsmans `stdin` is `FILE*` but it's pointing to a space in memory, doesn't it? — rullof, Jan 23 '14 at 12:40
maybe `pipe()` can create a internal `inode` that can be used as a file but has no existence in file system - but it is only for linux i think. — Dipto, Jan 23 '14 at 12:43
@Dipto Unfortunately I need something standardized and cross-platform. — rullof, Jan 23 '14 at 12:47
@rullof: yes, it points to a `FILE`. That in turn is a handle on an "actual" file, i.e. a file descriptor in kernel space. — Fred Foo, Jan 23 '14 at 12:55

score 0 · Answer 1 · answered Jan 23 '14 at 12:40

0

There is no support in C itself for this. You will need to use platform-specific means. If on Unix, you could combine memmap and fdopen, for instance. For other platforms, see the platform documentation.

answered Jan 23 '14 at 12:40

Magnus Reftel

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How can I create a file stream?

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