unix - In Linux, why is there a global /dev/stdin file for all processes?

Question

Shouldn't the standard input for different process unique? If so, shouldn't the path of the stdin file be like /dev/pid/stdin instead of a global /dev/stdin?

Does anyone have ideas about this?

Answer 1

/dev/stdin is unique because

• it is a symbolic link to /proc/self/fd/0
• /proc/self is a symbolic link only seen by your running process to its process-id

The /proc filesystem is a virtual (not real) filesystem which has the ability to show a different view to each process.

Further reading:

• Linux Filesystem Hierarchy: 1.14. /proc
• Red Hat Enterprise Linux 3: Reference Guide: Chapter 5. The proc File System