I still can't figure out many abbreviations' origin like rc, rc.d, share, proc...

I've heard someone says rc is "run command", .d is directory, but I'm not sure that's true.

Is there a table explaining what their source is?


2 Answers 2


rc is actually a fossil of an old batch facility, a runcom; the following is a quote from Brian Kernighan and Dennis Ritchie:

There was a facility that would execute a bunch of commands stored in a file; it was called runcom for "run commands", and the file began to be called "a runcom". rc in Unix is a fossil from that usage.

.d is a standard method to differentiate between a file and directory (as directories are a type of file, so they must have different names). It's often used to indicate that the files in that directory will be sourced for some purpose, usually to allow for modular configuration.

There is a good factsheet on stuff like this at the Indiana University website.

  • yes, another one perhaps is rc file is read configuration file, but runcom relation is more correct. +1 Chris :-) Jan 14, 2012 at 13:18
  • share and proc are obvious: share - accessible by any user usually. It is not an abbreviation. Proc comes from processes, and you will find all the running processes there, by number, id, name, etc. Jan 14, 2012 at 15:01
  • @PatkosCsaba - You won't find "all running processes there"... proc is process accounting.
    – Chris Down
    Jan 14, 2012 at 15:12
  • thanks. but i'm sorry that i think the page at Indiana University website is too few. it still lack a lot of thing like etc, tee, usr...
    – snow
    Jan 14, 2012 at 15:45
  • 1
    by the way, man hier can display description of the file system hierarchy, but not for my question
    – snow
    Jan 15, 2012 at 3:54

I got the answer from the following links. (The site is in Chinese, but the abbreviations and their meaning are in English.)



  • There are a few wrong ones, notably grep and /usr.
    – peth
    Mar 5, 2012 at 11:46

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