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ABOUT: A simple shell written in C. Project for OS Course at Florida Polytechnic University
AUTHOR: Luis Moraguez

Compiling

From within the project directory, do the folowing in the terminal:

mkdir ./bin
gcc -o ./bin/csh main.c csh.c -l readline

Running

To run the project after compiling, do one of the following:

Interactive Mode:
./bin/csh

Batch Mode:
./bin/csh {batch_file}

Built-ins

  • exit
  • cd
  • loop
  • path
  • export
  • help
  • about
  • history

exit

  • Signal handling for Ctrl-Z and Ctrl-C are ignored for the shell itself, but automatically re-enabled for any child processes spawned from csh.
  • exit command without any arguments will close csh
  • Ctrl-D at prompt will also close csh

cd

  • cd {directory} will change current working directory if destination exist
  • 0 arguments is invalid (requirements of project)
  • 1 argument with is correct
  • 2+ arguments is invalid

loop

  • loop {n} {command to execute} {optional: $LOOP} will loop a given command n times specified.
  • Examples:
Input:
loop 3 echo hello world

Output:
hello world
hello world
hello world
------------------------------------------------

Input:
loop 3 echo hello world $LOOP

Output:
hello world 1
hello world 2
hello world 3
------------------------------------------------

Input:
loop 3 loop 2 echo hello world $LOOP

Output:
hello world 1
hello world 2
hello world 1
hello world 2
hello world 1
hello world 2

path

  • path {directory_1} {directory_n} Will set the $PATH environment variable using space-delimited directories

export

  • export {VARNAME} {VALUE} Will set the named variable into the environment from the VALUE string provided

help

  • help Lists the shell built-ins

about

  • about Displays info about the shell

history

  • history Will print list of command history
  • Pressing the 'up' or 'down' arrow keys during prompt will move user through history list one entry at a time

Non-builtins

  • csh will let you execute non-builtin commands with ease because of its use of the 'execvp' syscall.

Simple Commands

  • Simple non-builtin commands, such as echo, can be parsed an executed currently

Looped Commands

  • Simple non-builtin commands can also be parsed and executed currently

Redirection

  • Output redirection to a file currently works for both write and append
  • Input redirection (WIP)

Action Items

  • Add output redirection (write and append)
  • Add input redirection
  • Add ability to set PATH and other environment variable using command similar to export (furture built-in)
  • Ensure that complex command combinations can be parsed/executed, eg. loop 5 echo world $LOOP >> ./result.txt
  • Add piping

Contributions:

Contributions are welcome. Fork the repo, make your changes, create a diff file, and email the diff file and your GitHub username to luis@moraguez.com. If the changes are approved, you will be added as a contributor to the repo.

Donations:

If this utility helped you with a project you're working on and you wish to make a donation, you can do so by clicking the donate button that follows. Thank you for your generosity and support!

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