C Shell

Developed on git repository here under folders Assignment2 & Assignment3. Refer for commit history

• Computer Systems Engineering - 1 (Assignment 2 & 3)
• By Kishan Sairam Adapa - 2018101026

Features

• All commands present in system's path work. This is done by using execvp.
• Directory from which shell is invoked is made home directory i.e, ~.
  • Home directory can be set to directory in which the executable is present.
  • This is done by doing these in main.c
    • Uncommenting line 42 to 50
    • Commenting line 53
• Some commands are implemented on own, they are
  • Built ins
    • cd
    • ls
    • pwd
    • echo
  • Process related
    • pinfo
  • Job related
    • jobs
    • kjob
    • overkill
• Processes are made background when & is used
• Pipes and Redirection are handled

Running Shell

• Run make in directory in which codes are present to generate executable main.out
• Run ./main.out to invoke shell
• Dependency: This shell implemented uses readline library which is not part of standard. Which needs to be installed in case make fails

Description of Files

Compiling

• Makefile

Header files

• cd.h
  • cd
• cronjob.h
  • cronjob
• echo.h
  • echo
• itoa.h
  • b10itoa
    • Conversion of base 10 integers to strings
    • Used to convert integers into strings for passing through pipes
• jobs.h
  • jobs
  • kjob
  • fg
  • bg
• ls.h
  • ls
• pinfo.h
  • pinfo
  • get_state
    • Stores current state of process in passed string given its pid
    • Used for updating data structure in which jobs are stored
• prompt.h
  • storePromptString
    • Stores what prompt to print in a string which is passed as parameter
    • Used to implement prompt using readline library
• run_command.h
  • run_cmd
    • Given correct parameters it runs the command passed through parameters in foreground
• signal_handlers.h
  • ctrlD
    • Handler for SIGQUIT (Ctrl + D)
  • ctrlC
    • Handler for SIGINT (Ctrl + C)
  • ctrlZ
    • Hander for SIGTSTP (Ctrl + Z)
  • sigchld_handler
    • Handler for SIGCHLD (Triggered whhen a child exits)

Implementation files (Contain Implemntation of functions in respective header files)

• cd.c
• cronjob.c
• echo.c
• itoa.c
• jobs.c
• ls.c
• pinfo.c
• prompt.c
• run_command.c
• signal_handlers.c

Shell program file - main.c

• Implements C Shell by using system headers and headers mentioned here