rshell

CS 100: Assignment 4

License

This project is licensed under GNU General Public License v3.0.

Introduction

rshell is a command shell written in C++, invoking syscalls fork, execvp, wait etc., with the capacity of:

• Print a command prompt (user@host: dir $).
• Handle complex commands connected by ||, &&, or ;.
• Support precedence operators ( and ).

The command should have the following form:

cmd        = [ ( ] executable [ argumentList ] [ connector cmd ] [ ) ] [ connector cmd ]
connector  = || or && or ;

Currently, we have the following built-in commands:

Command	Description
exit [code]	Exit rshell with a given code. If code is not given, 0 is used.
cd [dir]	Change working directory to a given dir. If dir is not given, $HOME is used.
test [flag] <path>	Test if a given path exists/is a dir/file based on flag.

We have also applied Doxygen syntax in our comment, which could generate nice documentation automatically by running doxygen commands.

Class Structure

• CmdBase, the abstract base class for commands.
  • CmdBinary, the base class for binary commands.
    • CmdAnd, the class for operator &&.
    • CmdOr, the class for operator ||.
  • CmdSequence, the class for command sequence sparaterd by semi-colon (;).
  • CmdUnary, the class for single (unary) command.
• CmdParser, the class for parsing user input into command tree.
• Executor, the class for executing command.

Installation

Run the following commands to install:

$ git clone https://github.com/coverxit/rshell.git
$ cd rshell
$ git checkout hw4
$ make
$ bin/rshell

Functionality

1. Print prompt with username, hostname and working directory.

rshell is able to print a prompt with the form user@host: dir $.

2. Print detailed error when execution failed.

When an error in execution occurred, rshell could print corrsponding information.

• Nonexistent commands. foo would print rshell: foo: No such file or directory.
• Failed execution. cd /foo would print rshell: cd: /foo: No such file or directory.

3. Execute combinations of operators.

rshell could handle commands such as

ls -al; echo hello && mkdir test || echo world; git status

Assume that directory tests exists, then executing above commands would print

[email protected]: rshell $ ls -al; echo hello && mkdir tests || echo world; git status
total 136
drwxr-xr-x  13 Shindo  staff    442 10 31 02:34 .
drwx------+ 11 Shindo  staff    374 10 31 01:47 ..
drwxr-xr-x  13 Shindo  staff    442 10 31 02:33 .git
-rw-r--r--   1 Shindo  staff    286 10 24 23:44 .gitignore
-rw-r--r--   1 Shindo  staff     27 10 29 21:55 .travis.yml
-rw-r--r--   1 Shindo  staff  35141 10 24 18:23 LICENSE
-rwxr-xr-x   1 Shindo  staff    473 10 24 23:44 Makefile
-rw-r--r--@  1 Shindo  staff   3925 10 31 02:34 README.md
drwxr-xr-x  10 Shindo  staff    340 10 31 02:33 src
drwxr-xr-x   7 Shindo  staff    238 10 31 02:33 tests
hello
mkdir: cannot create directory ‘tests’: File exists
word	
On branch exec
Your branch is up-to-date with 'origin/exec'.
Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)

	modified:   README.md

Untracked files:
  (use "git add <file>..." to include in what will be committed)

	bin/

no changes added to commit (use "git add" and/or "git commit -a")

4. Support changing precedence by using ( and ).

The parentheses () operators can be used to chagne the precedence of the returns of commands, connectors and chains of connectors. For example,

$ echo a && echo b || echo c && echo d

would print

a
b
d

With parentheses, we can change the precedence of connectors

$ (echo a && echo b) || (echo c && echo d)

that would print

a
b

5. Detect bad syntax.

For user input such as ls -al &&, rshell could detect the bad syntax.

• ls -al && would print rshell: bad syntax: unexpected token '&&'.
• || ls -al would print rshell: bad syntax: unexpected token '||'.
• ls &&&&&& echo oh would print rshell: bad syntax: unexpected token '&&'.
• ls &&& echo what would print rshell: bad syntax: unexpected token ' ', near '&'.
• ls &&| mkdir test would print rshell: bad syntax: unexpected token ' ', near '|'.
• ((((echo test) would print rshell: bad syntax: missing closing ')'.
• (echo test))) would print rshell: bad syntax: unexpected token ')'.
• (echo test)() would print rshell: bad syntax: unexpcted token '('.
• no-connector (echo test) would print rshell: bad syntax: unexpected token '('.
• (echo test) no-connector would print rshell: bad syntax: unexpected token 'no-conector'.
• echo "no closing would print rshell: bad syntax: missing closing '"'.
• echo "mix use' would print rshell: bad syntax: missing closing '"'.

Currently, we treat single & and | as illegal symbol, that is

• ls & echo oh would print rshell: bad syntax: unexpected token ' ', near '&'.

Known Issues

1. Cannot handle signals.

Currently, rshell does not handle signals such as Ctrl+C.

2. Cannot handle TABs.

Currently, rshell does not recognize tabs, treating them the same as spaces.

3. Cannot handle arrow buttons.

Currently, rshel cannot recognize arrow buttons such as ↑.

Valgrind Test

[rwu016@hammer rshell]$ valgrind --tool=memcheck bin/rshell
==5017== Memcheck, a memory error detector
==5017== Copyright (C) 2002-2012, and GNU GPL'd, by Julian Seward et al.
==5017== Using Valgrind-3.8.1 and LibVEX; rerun with -h for copyright info
==5017== Command: bin/rshell
==5017== 
[email protected]: rshell $ ls -al
总用量 80
drwxr-xr-x  6 rwu016 csmajs  4096 11月 18 14:33 .
drwx--x--x 17 rwu016 csmajs  4096 11月  9 18:59 ..
drwxr-xr-x  2 rwu016 csmajs  4096 11月 18 14:33 bin
drwxr-xr-x  8 rwu016 csmajs  4096 11月 18 14:33 .git
-rw-r--r--  1 rwu016 csmajs   307 11月 18 14:20 .gitignore
-rw-r--r--  1 rwu016 csmajs 35141 11月  2 16:20 LICENSE
-rwxr-xr-x  1 rwu016 csmajs   473 11月  2 16:20 Makefile
-rw-r--r--  1 rwu016 csmajs  6509 11月  2 16:20 README.md
drwxr-xr-x  2 rwu016 csmajs  4096 11月 18 14:33 src
drwxr-xr-x  3 rwu016 csmajs  4096 11月 18 14:21 tests
-rw-r--r--  1 rwu016 csmajs    27 11月  2 16:20 .travis.yml
[email protected]: rshell $ [ -f .travis.yml ] && echo "path exists"
(True)
path exists
[email protected]: rshell $ make clean
rm -f src/*.o
rm -rf bin
[email protected]: rshell $ make
g++ -c -Wall -Werror -ansi -pedantic -o src/main.o src/main.cpp
mkdir -p bin
g++  -o bin/rshell src/main.o
[email protected]: rshell $ exit  
==5017== 
==5017== HEAP SUMMARY:
==5017==     in use at exit: 150 bytes in 4 blocks
==5017==   total heap usage: 324 allocs, 320 frees, 123,413 bytes allocated
==5017== 
==5017== LEAK SUMMARY:
==5017==    definitely lost: 0 bytes in 0 blocks
==5017==    indirectly lost: 0 bytes in 0 blocks
==5017==      possibly lost: 0 bytes in 0 blocks
==5017==    still reachable: 150 bytes in 4 blocks
==5017==         suppressed: 0 bytes in 0 blocks
==5017== Rerun with --leak-check=full to see details of leaked memory
==5017== 
==5017== For counts of detected and suppressed errors, rerun with: -v
==5017== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)