Question

I want to read from a file by using its file descriptor. I can’t use its name because of assignment rules.

I obtain it by calling open and it works fine. At this moment I know that I have to use the read() function in order to read from it. My problem is that read() function requires as an argument the number of bytes to read, and I want to read a whole line from the file each time, so I don’t know how many bytes to read.

If i use for example fscanf(), it works fine with a simple string and I take back the whole line as I want. So my question is:

Is there any function like fscanf() which can be called with file descriptor and not with a file pointer?

Answer 1

When you say “have to use read()” I can’t tell if that’s your understanding of the situation given a file descriptor from open() or a restriction on some kind of assignment.

If you have a file descriptor but you’re more comfortable with fscanf() and friends, use fdopen() to get a FILE * from your fd and proceed to use stdio.

Internally it uses functions like read() into a buffer and then processes those buffers as you read them with fscanf() and friends.