/dev/stdin Dosyası

Giriş

Açıklaması şöyle. Yani Linux'ta bu dosyadan okumak aslında stin'in tüketmez.

The /dev/stdin, /dev/stdout, /dev/stderr and /dev/fd/x are special files that were added to various Unices in the 80s so the file descriptors of a process could be referred to by name.

On those Unices, opening /dev/stdin (a character device file) got you a file descriptor that was a duplicate of stdin (fd 0), so the equivalent of doing dup(0)³.

When Linux added a similar feature in the '90s, the implementation was significantly different and incompatible.

On Linux, those /dev/std..., /dev/fd/x files are not special character device files but symbolic links to /proc/self/fd/x, and those in turn are magic symlinks to the file that is opened on fd x.

So, opening /dev/stdin there is not the same as dup(0); it's opening the original file anew assuming you have permissions to do so, and from the start (not at the offset stdin is currently pointing within the file) and in the requested mode. That also means that if you're reading/writing/seeking from the fd you get which is independent from fd 0, you're not updating stdin's offset within the file.

Cygwin copied the Linux way when it added a similar feature in the 2000s. Most if not all other Unices behave the original way (when they support those /dev/fd/x at all).