S_IRUSR semantics in POSIX
linux, posix
Solution
The leading `S_` is just to identify what structure/function the constant goes with.
From `<sys/stat.h>`, the constants `S_IRUSR`, `S_IWUSR`, etc are possible values for the `st_mode` member for `struct stat` (used in `stat()` and friends). All the members of `struct stat` start with the prefix `st_`, and there are several `stat`-related macros that also start with `S_`. The convention is merely there to make matching structure names, member names, and constants easier.
Problem
I am learning the POSIX API, and I don't understand the logic behind some of the names. e.g. `S_IRUSR`, `S_IRUSR` What does What does the `S` stand for? I get that`R` and `W` are for read and write. But what naming convention followed by POSIX? Just like Win32 follows Hungarian Notation for naming, what does POSIX follow for their naming? For standards like POSIX, there must be documentation for it...