Unix Problem Set 1 Solutions
[Todd Sjoblom & Rusty Holleman]

Transcript of the solutions:

Problem 1
  [rchris@samsenior unix]$ mkdir /tmp/unix-course
  [rchris@samsenior unix]$ cd /tmp/unix-course
  [rchris@samsenior unix-course]$ su
  Password: ......
  [root@samsenior unix-course]# touch "I am owned by root"
  [root@samsenior unix-course]# ls
  I am owned by root
  [root@samsenior unix-course]# exit
  [rchris@samsenior unix-course]$ echo "Sweet potatoes" > I\ am\ owned\ by\ root
  bash: I am owned by root: Permission denied
  [rchris@samsenior unix-course]$ mv I\ am\ owned\ by\ root i_am_owned_by_root
  [rchris@samsenior unix-course]$ ls -l
  total 0
  -rw-r--r--    1 root     root            0 jui  9 13:34 i_am_owned_by_root
  [rchris@samsenior unix-course]$ ls -ld .
  drwxr-xr-x    2 rchris   adustaff     4096 jui  9 13:35 ./

This is possible since rchris owns the directory, and while file contents
cannot be changed, the filename is a property of the file's entry in that
directory.  Since rchris can modify the directory, the name of the file in
that directory can also be modified.

Problem 2
  [rchris@samsenior unix-course]$ mkdir A
  [rchris@samsenior unix-course]$ mkdir A/B
  [rchris@samsenior unix-course]$ chmod 711 A
  [rchris@samsenior unix-course]$ ls -l
  total 4
  drwx--x--x    3 rchris   adustaff     4096 jui  9 13:36 A/
  -rw-r--r--    1 root     root            0 jui  9 13:34 i_am_owned_by_root
  [rchris@samsenior unix-course]$ su
  Password: ......
  [root@samsenior unix-course]# su nobody
  [nobody@samsenior unix-course]$ ls
  A  i_am_owned_by_root
  [nobody@samsenior unix-course]$ ls A
  ls: A: Permission denied
  [nobody@samsenior unix-course]$ cd A
  [nobody@samsenior A]$ ls
  ls: .: Permission denied
  [nobody@samsenior A]$ cd B
  [nobody@samsenior B]$ ls
  [nobody@samsenior B]$ pwd
  /tmp/unix-course/A/B
  [nobody@samsenior B]$ exit


Problem 3
  [rchris@samsenior unix-course]$ touch -- -\\\\\\\\
  [rchris@samsenior unix-course]$ ls
  -\\\\  A/  i_am_owned_by_root
It's not possible to create a filename with internal forward slashes, since
these are the builtin directory separator.

  [rchris@samsenior unix-course]$ mv -- -\\\\\\\\ \~cannot_do_it
  [rchris@samsenior unix-course]$ ls
  A/  i_am_owned_by_root	~cannot_do_it
  

Problem 4
  [rchris@samsenior unix-course]$ cd ~/january
  [rchris@samsenior january]$ ls
  p1/  p2/  p3/
  [rchris@samsenior january]$ ls p1
  CosFunc.class		 FuncTest3.class     PQueue.java	  RFunc.class	      SinFunc.java~
  CosFunc.java		 Function.class      PQueue.java~	  RFunc.java	      TestClass.tar
  FuncTest$ExpFunc.class	 Function.java	     PQueueTest.class	  RFunc.java~	      doc/
  FuncTest$LogFunc.class	 Function.java~      Poly.class		  RFuncLib.class      notes
  FuncTest$SinFunc.class	 FunctionTest.class  Poly.java		  RFuncLib.java       notes~
  FuncTest.class		 FunctionTest.java   Poly.java~		  RFuncLib.java~      orig-FuncTest2.class
  FuncTest2.class		 FunctionTest.java~  PolyTest.class	  RFuncLibTest.class  prob3/
  FuncTest3$ExpFunc.class  MyPolyTest.java     PolyTest.java	  RFuncTest.class     prob4/
  FuncTest3$LogFunc.class  PQueue$lnode.class  PolyTest.java~	  SinFunc.class       prob5/
  FuncTest3$SinFunc.class  PQueue.class	     PriorityQueue.class  SinFunc.java	      tmp/
  [rchris@samsenior january]$ wc -l `find ./ -name "*.java"` | tail -1
     3700 total
  [rchris@samsenior january]$