CIS2500 Lab Two

There are no tasks or coding lessons this week, we just want to make sure that you have gotten on board with Git and are comfortable with the core concepts required to complete your first assignment.

Agenda

1. Moodle Survey
2. Git
3. Review
4. Parsing
5. A1 Advice

Moodle Survey

Before we begin, Justin wants everyone to take a moment to fill out his survey on Moodle.

GIT Setup

Setup Your Profile

Execute the following commands. The ‘user.name’ and ‘user.email’ parts aren’t placeholders for anything and meant to be entered as shown. The parts between brackets are placeholders and should be replaced with your credentials, omitting the brackets when doing so.

• git config --global user.name <usernameHere>
• git config --global user.email <emailHere>

Login Credentials

• Your Git Username is the same as your SSO login
• Your Git password is your SOCS password
  • This is (likely) different than your SSO password
  • Default is your 7 digit student number
  • Can change using passwd after SSHing into a UofG server (assuming you know your old password to login)
  • Alternatively, by visiting the Forgotten Password Page

Basic Commands (Minimum Needed to Submit Assignment)

• git clone
  • Downloads a repository from a server
  • Only done to initially retrieve a repository (use pull to update)
  • Often can be done w/o any sort of login credentials (ie. public Github repos)
• git add
  • You need to add files before they will be tracked by Git
  • Adding a directory will add its contents recursively
• git commit -m
  • Logs changes which you have made and takes a snapshot of the work you have done (to tracked files)
• git push
  • Uploads commits to the remote server

Other Helpful Commands

• git pull
  • Downloads any commits added since your last clone or commit
• git status
  • See an overview of changes since your last commit/ clone
  • Useful to verify which files are going to be included/ omitted
• git log
  • See an overview of commits you have made
• git checkout
  • Switch your ‘snapshot’ to another one
• git rm
  • ‘Untracks’ a file
  • Will actually rm the file too so be careful
  • Use rm --cached if you want to keep your file but just remove it from git if you added it accidentally

Review

Getting arguments in from the command line using argc and argv

• Recall that for both argc and argv, your program name itself is always considered the first argument
• Recall that argc is the argument counter
  • your program name itself will increment the counter by 1
  • …so if you where to pass one argument to your program, argc would be 2
• Recall that argv is a 2D char array which holds the strings which themselves
  • Like all arrays in C, their index begins with 0
  • …so your program name is contained in argv[0]
  • …so if you where to pass one argument to your program, argv[1] would be it

Opening files

• Recall that we use fopen to open a file
• Always check to ensure that your file was able to be open
• Always remember to use fclose to close your file when you are done accessing it

Reading lines from a file

• Recall how to use fgets to read in a line from a file.

Parsing

strtok: A Blessing and a Curse

strtok is useful for parsing strings within a loop. It has some caveats to take into consideration though. You by no means need to use it for this assignment, however it may be helpful to know.

• char* strtok(char* str, char* sep);
• str is the string that you want to parse
• sep is a list of the delimiter that you want to use
• Returns a char* token; the substring between either the start of your string/\0 and the next eliminator or newline/EOF/\0.
  • Does not allocate memory for you so there is no need to free this reference (if you don’t know what this means yet thats okay, disregard)
• Works by replacing the delimiter in your string with nul terminators (\0)
  • Is destructive; modifies your passed string
• on subsequent calls to strtok, pass NULL as the str argument to continue where you left off
  • Keeps an internal static reference of where you where last
  • Cleared when you switch strings

Other Possible Topics of Interest

• How to read in a char at a time file from a file stream
  • man getc
  • Returns an int, which cat be treated like a char
  • Returns EOF at the end of file
  • Note that EOF is not actually a character
• Know when we’re done reading from a file
  • man feof
  • Useful when looping with fgets

Advice for A1 and Beyond

Stay for my office hours after the lab to discuss specific concerns and strategies. In general, keep the following in mind when coding:

• Have a game plan before you start
• Be prepared to take another approach
• Strive for elegance, not cleverness
• Refer to the requirements (frequently)
• Don’t treat testing and debugging as an afterthought