Simple implementation of a Linux Shell in C

How to execute

Clone the repository, navigate to its path and use the following command in terminal:

make all
./shell

Functionalities:

Builtin commands:

• fg <PID>: put a process in foreground.

• bg <PID>: put a process in background.

• jobs: list jobs executing in background.

• kill <PID> <SIGNAL_NUMBER>: send a signal to a process.

• history: list the last 50 commands.

• export <ENV_VARIABLE>=<NEW_VALUE>: set a environment variable. You may use it to add directories to MYPATH. Example:

`export $MYPATH=$MYPATH:/foo`.

• cd <PATH>: change current directory. One can pass the relative or absolute path.

• set: list environment variables.

• echo <STRING>: display the string to stdout. You may use it to print value of environment variables (example echo $MYPATH).

• exit: close shell (You can press <CTRL+D> as well).

You can execute programs that are on PATH and use 'Pipe' between consecutive commands using the vertical bar |. Multiple pipes are allowed.

Input and output redirection implemented (< for stdin, > for stdout, 2> for stderr).

Execute in background with & at the end of the command.

SIGCHILD handler implemented. This avoids zombie process.

SIGINT handler implemented. This means that you can't close the shell pressing <CTRL+C>, however you can kill the current program executing in foreground.

SIGTSTP handler implemented. This means that you can't stop shell process by pressing <CTRL+Z>, however you can stop the current program executing in foreground. You can see the stopped program on jobs.

Environment variables MYPATH and MYPS1 are equivalent to PATH and PS1, respectively. At the beginning, MYPATH value is equal to PATH and PS1 is equal to tecii$ .