Project 3 --Files, Directories, and Permissions

NOTE: This assignment, like the other projects in this class, is due at a particular time, listed above. This means that if you are even a minute late, you lose 20%. If you are worried about potentially being late, turn in your project ahead of time. Do this by submitting it electronically before it is due and giving the hard copy to me during office hours or by sliding it under my office door before it is due. Do not send assignments to my personal email address. Do not leave hard copies in my departmental mail box or attempt to give them to departmental staff (who cannot and will not accept them).

In your previous assignment, you took the first step toward the development of a graphical PDF browser by linking together a PDF to image conversion tool with a web browser. However, gbPDF Version 1.0 lacked some functionality we might want in a graphical PDF browser, such as browsing through zipped files of PDFs.

In this assignment, you will take the second step toward the development of a graphical PDF browser. This is only the second step, since you have not yet learned in this class about mechanisms for passing the input and output of processes to one another (although you will!), and you are not assigned the job of creating a nice GUI front end for your PDF browser. Still, it will let you gain experience with the basic mechanisms for dealing with files, directories, and permissions.

You are to create a program called gbPDF2 that behaves as follows:

1. If the user invokes gbPDF2 by handing it one or more files with the extension .pdf or .PDF, it will behave almost exactly as described for the original gbPDF described in Project 2. The one exception to this is that gbPDF2 will not exit as soon the web browser is launched. Instead, gbPDF will wait for the web browser to exit, then gbPDF will delete all .png files it created, then gbPDF2 itself will exit. If there are any problems deleting the .png files, gbPDF2 should notify the user of that fact and exit with exit code 4. Otherwise, gbPDF2 should exit with exit code 0.


2. If the user invokes gbPDF2 by handing it one or more directory names, gbPDF2 will recursively read through each named directory and its subdirectories searching for files that have the .pdf or .PDF extension. If there are any problems reading through a directory or its subdirectories, gbPDF2 should notify the user of that fact and exit with exit code 5. Otherwise, gbPDF2 should treat these files as it would PDF files given on the command line. (That is, create two sets of .png files, full sized and thumbnails, …).


3. If the user invokes gbPDF2 by handing it one or more filenames with the extension .zip, .tar, or .tgz, gbPDF2 will behave as described below.

   For each "package file" given (with the extension .zip, .tar, or .tgz) gbPDF2 will do the following:

   1. Create a directory to hold the contents of the package file. This directory should have the same name as the name of the package file, except that it should start with a '.' (so that the directory is "hidden") and it should not have the .zip, .tar, or .tgz extension on the end. This directory should be created such that only its owner has read, write, and execute permissions on it. If there are any problems creating this directory or setting its permissions, gbPDF2 should notify the user of that fact and exit with exit code 6. Otherwise, gbPDF should proceed to Step 2.
   
   
   2. Unpack the contents of the package file into the directory created in Step 1. If there are any problems unpacking the file into this directory, gbPDF2 should notify the user of that fact and exit with exit code 7. Otherwise, gbPDF should proceed to Step 3.
   
   
   3. Recursively read through the directory created in Step 1 for any files placed there or in any of its subdirectories in Step 2 that have the .pdf or .PDF extension. If there are any problems reading through the directory or its subdirectories, gbPDF2 should notify the user of that fact and exit with exit code 5. Otherwise gbPDF2 should treat these files as it would PDF files given on the command line. (That is, create two sets of .png files, full sized and thumbnails, …).
   
   
   4. Once gbPDF2 has deleted all .png files it created (see Step I, above), gbPDF2 will delete all files and directories it created by unpacking files. If there are any problems deleting these files and directories, gbPDF2 should notify the user of that fact and exit with exit code 8. Otherwise, gbPDF2 should exit with exit code 0.



4. If the user invokes gbPDF2 with filenames with any other extension or none at all and/or with any other command line argument(s), gbPDF2 should print a usage message to the terminal and exit with exit code -1. Note that the rules on extensions mentioned here apply only to file names, not to directory names.

You will turn in both a hard copy and an electronic copy of your assignment. Electronic copies must be submitted to the appropriate drop box in D2L for the course. Do not send them to my email address.

Both the hard copy and the electronic copy will contain a cover sheet documenting group membership and contributions (see below), all source code you created for gbPDF2, and a write-up of 1/2 to 1 page (roughly 80 characters per line, 50 lines per page) explaining the data structures and algorithms used in your code. This page limitation does not include figures used in your explanations, which are encouraged and may take up any amount of space. (The explanations do not remove the requirement that your code be well commented.)

The electronic copy will also contain an executable for gbPDF2 which should be called gbPDF2.

Your source code should be well structured and well commented. It should conform to good coding standards (e.g., no memory leaks).

You may write your program from scratch or may start from programs for which the source code is freely available on the web or through other sources (such as friends or student organizations). If you do not start from scratch, you must give a complete and accurate accounting of where all of your code came from and indicate which parts are original or changed, and which you got from which other source. Failure to give credit where credit is due is academic fraud and will be dealt with accordingly.

As noted in the syllabus, you are required to work on this programming assignment in a group of at least two people. It is your responsibility to find other group members and work with them. The group should turn in only one (1) hard copy and one (1) electronic copy of the assignment. Both the electronic and hard copies should contain the names and student ID numbers of all group members. If your group composition changes during the course of working on this assignment (for example, a group of five splits into a group of two and a separate group of three), this must be clearly indicated on your cover sheet (see below), including the names and student ID numbers of everyone involved and details of when the change occurred and who accomplished what before and after the change.

Each group member is required to contribute equally to each project, as far as is possible. Your cover sheet must thoroughly document which group members were involved in each part of the project. For example, if you have three functions in your program and one function was written by group member one, the second was written by group member two, and the third was written jointly and equally by group members three and four, your cover sheet must clearly indicate this division of labor.

Note that all personally identifying information (names, student ID numbers, 4x4s, etc.) must only be included on the cover sheet and nowhere else in the project materials.

For determining which files and directories were created by gbPDF2, you may use time stamps and assume that files or directories created after gbPDF2 was invoked and in subdirectories of the directories on which gbPDF2 was invoked were created by gbPDF2. Note that this is not a good assumption to make in general and is only allowed in this project because you have not yet learned sufficient IPC to do this in a better way.