System Inspector

Our journey through the operating system starts in userland (user space), outside the kernel. In this project, we’ll implement a Unix utility that inspects the system it runs on and creates a summarized report for the user. If you’ve ever used the top command from a shell, our program will be somewhat similar. To give you an idea of how your program will work, here’s a quick example: [magical-unicorn:~/P1-malensek]$ ./inspector System Information ------------------ Hostname: magical-unicorn Kernel Version: 4.20.3-arch1-1-ARCH Uptime: 32 minutes, 35 seconds Hardware Information -------------------- CPU Model: AMD EPYC Processor (with IBPB) Processing Units: 2 Load Average (1/5/15 min): 0.15 0.06 0.01 CPU Usage: [##########----------] 50.3% Memory Usage: [--------------------] 4.6% (0.0 GB / 1.0 GB) Task Information ---------------- Tasks running: 88 Since boot: Interrupts: 44349 Context Switches: 88340 Forks: 421 PID | State | Task Name | User | Tasks ------+--------------+---------------------------+-----------------+------- 1 | sleeping | systemd | root | 1 2 | sleeping | kthreadd | root | 1 3 | idle | rcu_gp | root | 1 4 | idle | rcu_par_gp | root | 1 (the entire list of processes is printed -- truncated for brevity) To get this information, you will use the proc, the process information pseudo-filesystem. While there are other ways to get the information displayed above, you are restricted to using proc in this assignment. There are two great resources for finding out what information is available in proc: Simply cd /proc in your shell and then run ls to view the files. You’ll see process IDs and several other virtual files that are updated dynamically with system information. Each line shown above in the process listing corresponds to a numbered directory in /proc. Check out the man page: man proc. The manual has a complete description of every file and directory stored under /proc. For a quick example, try running cat /proc/uptime. You’ll see the number of seconds the system has been running printed to the terminal. In this assignment, you will get experience working with: The open(), read(), and close() system calls for reading file data Tokenizing text files opendir and readdir functions for listing directory contents stat for getting file information getpwuid() to map user IDs to user names Argument parsing with getopt Load averages, calculating CPU usage, and Linux tasks Each portion of the display can be toggled with command line options. We’ll let the program do the talking by printing usage information (-h option): [magical-unicorn:~/P1-malensek]$ ./inspector -h Usage: ./inspector [-ahlrst] [-p procfs_dir] Options: * -a Display all (equivalent to -lrst, default) * -h Help/usage information * -l Task List * -p procfs_dir Change the expected procfs mount point (default: /proc) * -r Hardware Information * -s System Information * -t Task Information So the task list, hardware information, system information, and task information can all be turned on/off with the command line options. By default, all of them are displayed. Pay particular attention to the -p flag. This allows us to change the directory where proc is mounted (/proc by default). We will use this option to test your code with our own pre-populated copy of proc.