Mumsh shell project

I. Build badge

The whole program contains 6 files, main.c, execute.c, redirection.c, handler.c, parser.c and header file p1.h.

• main.c: main program
• execute.c: contains all the execution functions and built-in command implementation (e.g. fork to open child process)
• redirection.c: contains all the functions processing I/O redirection check and implementation
• handler.c: contains error handler and ctrl+C interrupt handler
• parser.c: contains all the functions transforming the input string intro parser, which contains segments of strings better for execution.
• p1.h: contains all the function declaration, enum declaration

The main code structure and logic are as follows.

(a) The main function void mumsh(void) starts, and there's a read-parse-execute loop continuously read the input from users.

(b) Then there're several parser function to process the input string, such as checking & for background process, inserting space before and after >, <, |, checking if the command is completed, finally break it into several segments stored in parser.

(c) Then the mumsh function calls function void execute_process (written in recursion), which in our father process, check the I/O redirection if any from parser, break the segments if detecting |. And then fork() to create child process, implement I/O redirection, execute the corresponding commands.

(d) Harvest all the child processes, and then continue reading input from users.

II. Build & installation instruction

$ mkdir cmake-build-debug && cd cmake-build-debug
$ cmake -DCMAKE_C_COMPILER=clang ..
$ make

III. Running instructions

In your terminal run ./mumsh, then you can enter the mumsh interface.

• single commands without arguments, e.g. ls.
• commands with arguments, e.g. ls -a.
• File I/O redirection (also support bash style redirection syntax), e.g. cat < 1.txt 2.txt > 3.txt 4.txt.
• Pipe support, also runs in parallel, supports arbitrarily deep "cascade pipes", and can be combined with I/O redirection.
• Support CTRL-D and CTRL-C
• Support built-in commands for cd and pwd.
• Support quotes and incomplete quotes (will output '>'), e.g. echo "de'f' ghi" '123"a"bc' a b c
• Wait for the command to be completed when encountering >, <, or |.
• Support background process and jobs commands.

IV. Author information

Pingchuan Ma, senior undergraduate student from UM-SJTU JI, email: hensonma@sjtu.edu.cn