hw1-ls

adding the ls command to your shell

coding requirements

Write a C++ program that implements a subset of the GNU ls command. In particular, you must support: the -a, -l and -R optional flags; and the ability to pass in zero, one, or many files. Notice that the GNU ls command handles files and folders differently, and you must reproduce this functionality exactly. For a refresher on how to use the ls command effectively, you can watch this video tutorial.

To implement ls, you must use the opendir, closedir, readdir and stat syscalls. For details on the use of these functions, visit their man pages and the syscalls tutorial.

Previous cs100 students have written up code that reads the files in the current working directory, with documentation explaining the process. The code may be found here, within the syscalls tutorial.

submission instructions

You will add this code to your rshell project on github. Create a branch called ls and do all of your work under this branch. When finished, merge with the master branch and create a tag called hw1.

To download and grade your homework, the TA will run the following commands:

$ git clone  http://github.com/yourusername/rshell.git
$ cd rshell
$ git checkout hw1
$ make
$ bin/ls

You should run them as well to verify that you've submitted your code successfully.

project structure

All source files created for this program should be in your project's src folder.

You will have to modify the Makefile to include a target called ls which builds your ls program. The all target should build both rshell and ls. Both binaries should be placed in the bin folder. Remember that binaries should not get added to your git repo, and you will be penalized if they are.

testing

Again, the tests you choose will be the most important part of your grade.

Remember that the commands ls -l -R, ls -R -l, ls -lR and ls -Rl should all do the same thing. You must consider how these flags interact with the -a flag and the optional file parameters.

As with your previous assignments: Your tests directory will contain a file called ls.script that contains all of the test cases you tried. You will generate the file using the script command, and it must be succinct (i.e. it cannot have unnecessary commands in it). You should use comments in your script to document what you are testing with each test case.

IMPORTANT: If you are unsure if your test cases are sufficient, ask one of the instructors to review them before the deadline.

collaboration policy

You MAY NOT look at the source code of any other student.

You MAY discuss with other students in general terms how to use the unix functions.

You are ENCOURAGED to talk with other students about test cases. You are allowed to freely share ideas in this regard.

You are ENCOURAGED to look at GNU ls's source code for inspiration.

grading

25 points for the optional file parameters

25 points for the -a flag

25 points for the -l flag

25 points for the -R flag

extra credit

The GNU ls utility displays different types of files in different colors/fonts using ANSI escape codes. You will receive up to 15 points extra credit if your ls command has this ability. In particular, you should print directories in blue; executables in green; and hidden files (with the -a flag only) with a gray background. These effects should be combinable. So if you have a hidden directory, it should be displayed as blue text on top of a gray background.

additional resources

Here is a complete list of resources created by previous cs100 students that might help with this assignment:

• how to use syscalls

• STL Map

• video: how to use the ls command.

• video: guide to directories.