UNIX compatible shell - k_shell

A shell implemented in C/C++. Intended to obtain a better understanding of:

• UNIX interface
• Process creation and handeling
• Lex
• Yacc
• Pipes
• Regular expressions
• Pointer & string manipulation
• Bash scripting
• Debugging tools

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Project layout

• Makefile: run "make" in and it will create an executable called "shell"
• command.cc : C++ class implementation for a command in the shell. Also holds the main method
• shell.l : Lex file. Also includes implementation for subshell
• shell.y : Yacc file. Also includes wildcard implementation
• ks : Bash script to kill all instances of the shell in case shell hangs. Debugging tool
• read-line.c : C implementation for the line editor for the shell
• regular.cc : test program to use regexec
• cat_grep.cc : A C program to create an executable that works like "cat file | grep word > outfile"
• tty-raw-mode.c : helper for line editor
• printErr.c : program to test read/write IO

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Working features (somewhat similar to csh)

• IO Redirection between commands
• Pipes between commands
• Background and Zombie process handling
• Environment vairables
• Words and special chars
• cd command
• Wildcarding
• Quotes and escape chars
• Ctrl-C handeling (exit command)
• Robustness (limiting the no. of crashes)
• subshell
• tilde expansion
• Line editor
• left
  • right
  • backspace
  • home
  • end
  • Ctrl+?
  • Ctrl+e
  • Ctrl+a
  • Ctrl+d
  • del

Extra features

• "debug" command : enter "debug on" and see dubugging information for the shell.
• Line editor
  • Ctrl+l : clears current line
  • ks : (debugging tool) bash script to kill all instances of the shell if it hangs

TODO (For the motivated)

• Line editor
  • history (unstable. history is recorded correctly. set if(...) statement to if(1) in read-line.c:164 to see recorded history )