Read from file or stdin

Question

I am writing a utility which accepts either a filename, or reads from stdin.

I would like to know the most robust / fastest way of checking to see if stdin exists (d

Answer 1

You may want to look at how this is done in the cat utility, for example.

See code here. If there is no filename as argument, or it is "-", then stdin is used for input. stdin will be there, even if no data is pushed to it (but then, your read call may wait forever).