Simple Unix shell in C.

• gcc shell.c -lpthread -o shell
• ./shell

• Supports a semicolon separated list of commands with their arguments.
• Can create background processes with <command> & and a message is displayed when finished.
• Input and Output redirection with <, > and >> have been implemented.
• Command redirection using | (any number) has been implemented.
• I/O redirection and Pipe redirection also work together.
• cd, pwd, echo and quit are implemented as built-in commands.
• pinfo is a command which when used without arguments prints process related info of the shell. pinfo <pid> prints process related info of the process with the given pid.
• jobs is a command which prints a list of currently executing processes in order of their creation, particularly background processes, along with their pid.
• kjob <jobNumber> <signalNumber> sends the indicated signal to the job with the given job number (got from jobs).
• fg <jobNumber> brings the background job with the given job number to the foreground.
• overkill is a command which kills all the background jobs.
• CTRL-Z changes the state of the currently running foreground job to STOPPED and pushes it to the background.
• Only quit exits the shell and all other keyboard interrupts are ignored.
• Error handling has been taken care of and appropriate messages are displayed.