UGC NET CSE | June 2016 | Part 2 | Question: 39

Question

In UNIX, ____ creates three subdirectories; 'PIS' and two subdirectories 'progs' and 'data' from just created subdirectory 'PIS'

• A. mkdir PIS/progs PIS/data PIS
• B. mkdir PIS progs data
• C. mkdir PIS PIS/progs PIS/data
• D. mkdir PIS/progs data

Answer 1

C is Ans

mkdir PIS PIS/progs PIS/data

Creates PIS parent directory first then inside that two sub directories namely progs and data are  created.

But I would do like this to get the same effect:-

mkdir -p PIS /{progs,data}

The above creates the top-level directory PIS, along with all of the subdirectories PIS/progs,PIS/data,).

How does it work? There are two things of note about the command above:

The -p flag: This tells mkdir to create any leading directories that do not already exist. Effectively, it makes sure that PIS gets created before creating PIS/progs.

The {} lists: The technical name for these is "brace expansion lists". Basically, the shell interprets this as a list of items that should be appended individually to the preceding path. Thus, a/{b,c} is expanded into a/b a/c.