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I would like to have a FILE* type to use fprintf.
I need to use fdopen to get a FILE* instead of open that returns an int.
But can we do the same with fdopen and open? (I never used fdopen)
I would like to do a fdopen that does the same as :
open("my_file", 0_CREAT | O_RDWR | O_TRUNC, 0644);
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If fdopen() returns NULL, use close() to close the file. If fdopen() is successful, you must use fclose() to close the stream and file.
The open function creates and returns a new file descriptor for the file named by filename . Initially, the file position indicator for the file is at the beginning of the file.
fcntl(fd, F_GETFD) is the canonical cheapest way to check that fd is a valid open file descriptor. If you need to batch-check a lot, using poll with a zero timeout and the events member set to 0 and checking for POLLNVAL in revents after it returns is more efficient.
So first unused file descriptor is 3 in file descriptor table. After that in close() system call is free it this 3 file descriptor and then after set 3 file descriptor as null. So when we called second open(), then first unused fd is also 3.
fdopen takes a file descriptor that could be previously returned by open, so that is not a problem.
Just open your file getting the descriptor, and then fdopen that descriptor.
fdopen simply creates a userspace-buffered stream, taking any kind of descriptor that supports the read and write operations.
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