This is the third assignment for IB016, semester spring 2016.

Name: Name Surname

UID: 123456

Tree

This time your task is to implement a simplified version of unix utility tree, which can print a directory tree on the terminal. For more details about tree, you can refer to man tree or to its online version, for example http://linux.die.net/man/1/tree.

Your version should support at least the following options:

• --help -- will print help for your version of tree, including a short description and available options.

  • The format of the output can be arbitrary, however, it must contain short information about all options.
  • Help is printed on the standard output.

• --version -- prints the version and optionally the licence and authors of the program.

  • The format of the output can be arbitrary.

• -a -- All files are printed.

  • By default, tree does not print hidden files (those beginning with a dot .). In tree should never print the file system constructs . (current directory) and .. (previous directory).

• -d -- List directories only.

  • By default, tree prints both files and directories.
  • In combination with -a it prints hidden directories (but no files).

• -L level -- Max display depth of the directory tree.

  • The level must be greater then 0.
  • If more than one -L options are given, the latest is used.

• --noreport -- Omits printing of the file and directory report at the end of the tree listing.

  • If this option is not given tree will print short summary at the end, in the form "X directories, Y files" where X and Y are the numbers of printed directories and files.
  • Symbolic links can be counted as files, or as the GNU tree does, counted as files if they refer to files (or are invalid) and as directories if they link to directories.

• -U -- Do not sort.

  • Disables --dirsfirst
  • Without this option, the content of each directory is sorted lexicographically by the name.

• --dirsfirst -- List directories before files.

  • This option is disabled when -U is used.
  • Without this option, sorting is applied regardless of the entry type.
• If both --dirsfirst and -U are used, the effect is given by the last one.

If the program is run with wrong arguments, it prints help (as with --help) to the standard error output and exits with nonzero exit code.

If the program finds a directory it cannot access, it will print the name of the directory (and not descent into it) and it will print a relevant error message on the standard error output. It will also exit with a nonzero exit code in this case.

The implementation must be fully in Haskell, it must not call any external utilities. You are allowed to use any libraries from https://downloads.haskell.org/~ghc/latest/docs/html/libraries/. You can also use a library for command line parsing (even if it is not listed in the above libraries, for example System.Console.GetOpt). However, it would be nice if you used monoid-based command line parsing from the lectures.

The format of the output should be same as for unix utility tree, small deviations might be tolerated.

Example

test
├── file01.txt
├── file02.txt
├── sub_01
│   ├── file01_01.txt
│   ├── file01_02.txt
│   └── sub_01_01
│       ├── file01_01_01.txt
│       └── file01_01_02.txt
├── sub_02
│   ├── file02_01.txt
│   ├── file02_02.txt
│   ├── sub_02_01
│   │   ├── file02_02_01.txt
│   │   └── file02_02_02.txt
│   └── sub_02_02
├── sub_03
└── sub_04

7 directories, 10 files

For more examples use tree for example on aisa.

Tip: design of the appropriate data structures will help you a lot.