Filesystems, Disks and Memory

As I read the source code of unix I wonder where u_ofile[0](it should be stdout) link to ?

Does it link to a file structure like ordinary files?

That's up to the program that spawns the process. As a default, most shells will default stdout to /dev/tty. But if, for example, you do:
someprog > /dev/null
then stdout will be pointing to /dev/null.

you mean u-ofile[0] connects to struct tty?

or it still connects first to struct file then to inode?

if it is an ordinary file it will connect like this:

process pa
u-ofile
-------------
| stdin |
-------------
| stdout |
-------------
| stderr | file inode
------------- -------------- ------------
| |------------------------> | |--------->| |
------------- -------------- ------------



Is it like:

process pa
u-ofile
-------------
| stdin | tty
------------- ----------------
| stdout |-----------------------> | |
------------- ---------------
| stderr |
-------------

?

right??

sorry i don't know how it become like this .....hope i will be understood!

you mean u-ofile[0] connects to struct tty?

or it still connects first to struct file then to inode?

if it is an ordinary file it will connect like this:

process pa

u-ofile
stdin
stdout
stderr
fd1--------->file structure---->inode

Is it like:

process pa
u-ofile
| stdin |
| stdout |--------->tty
| stderr |

?

right??

The internal detail vary based on the kernel and the details that you are quoting are alien to me. The fd table points to a system file table entry. The first one is called stdout. With the kernels I know, the file table will then point to a vnode.

/dev/tty and /dev/null are not called ordinary files. They are called special files because they actually connect to a driver.

But stdout is opened just like every other file...well it could be a socket. But the kernel does not treat fd 0 any differently than, say, fd 5.

O! so the fd0 is also first points to a file structure right ?

thanks,you really help me a lot with my final exam.

Can you introduce me some reference about this topic?

thanks!