NJU OS Labs 2018 This is the personal implementation of the 2018 spring OS Labs at Nanjing University instructed by Dr. Jiang Yanyan. The project is opensourced under GPL v3. * Warning to my dear classmates * You will be at your own risk if you use any of the code in this repository. = pstree.c = This project implemented a miniature of the classic UNIX command pstree by reading kernel information from the /proc directory(thus makes it only compatible with Linux), which lists all the processes running in the form of a tree. The program implemented 3 options wwhich are -p, --show-pids: which prints out the PID of each process. -n, --numeric-sort: which sorts all the processes by their PIDs. -k, --kernel-threads: which prints out the kernel threads along side with normal output. Also a -V or --version option is available to provide version informaion of the program. = perf.c = Performance evaluator which lists all the system calls during the process and the time they cost. (It is in fact no more than a *beautiful* shell of "strace -T") = crepl.c= C read-evaluate-print-loop. It takes the input of a valid C code (but with some limitations) to provide an interactive C code shell. Limitations includes 1. Only int functions are accepted and registered. 2. All other code will be regarded as an expression. 3. A function or an expression must take and only take a single line. 4. All other input's results will be undefined.