OS-SHELL

INTRODUCTION

Created an interactive shell that program that can create and manage new processes.

Execution Steps:

• Type command 'make' to run the makefile.
• './os' to execute the user-defined shell.

FEATURES

• Builtins:
  1. cd
  2. pinfo
  3. exit
  4. pwd
  5. ls
  6. nightswatch
  7. jobs
  8. kjob
  9. fg
  10. bg
  11. overkill
  12. setenv
  13. unsetenv

Functionalities

Specification 1:

• Displays appropriate shell prompt considering the directory in which the program is executed as Home directory.

Specification 2:

• 'cd', 'pwd', and 'echo' implemented as per the requirements.
• Extra functionality of displaying environment variables like $HOME, $PWD added in 'echo' command.

Specification 3:

• Typing only 'ls' gives the output as expected.
• It works for the flag '-l' and '-a'.The ordering or the number of '-l' and '-a' does not affect the execution of the command. Arguments with file names can be given with the command.

Specification 4:

• System commands running using 'execvp'.

• Foreground processes running as per requirements. That is the shell is stopped until the process is terminated if it starts in foreground.
• Background processes running as per requirements. Any command invoked with "&" is treated as background command. This implies that your shell will spawn that process and doesn't wait for the process to exit. It will keep taking user commands.

Specification 5:

• 'pinfo' command implemented. It fetches its data from the file /proc//state and executable path from /proc//exe.

Bonus:

If the background process exits then the shell displays the appropriate message to the user.