According to POSIX, sys/stat.h shall define a bunch of macro constants such as S_IRUSR. The "R" part obviously means "Readable" and the "USR" part "User" (the owner of the file.) Then what about the S_I part?

  • 1
    The etymology tag question should go to Meta.
    – Jeff Schaller
    Commented Jul 13, 2017 at 11:20
  • 2
    S for "stat", and I for "inode"? It's common to prefix identifiers to avoid confusion, and this part is probably very old ...
    – dirkt
    Commented Jul 13, 2017 at 11:31
  • To avoid confusion and clashes with other values, since those are #defined constants and they don't have separate namespaces
    – ilkkachu
    Commented Jul 13, 2017 at 11:33
  • 1
    Related question: unix.stackexchange.com/questions/224701/…
    – nodakai
    Commented Jul 14, 2017 at 6:07


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