Running Kalpesh (The Shell)

• type "make" after cloning the repo and cding into it

• run ./kalpesh

• external commands supported:

  1. ls : lists all files not starting with .

     • -a : lists all files including those starting with .

     • -1 : lists each file on newline

     • Corner Cases Defended

       1. if invalid option is passed into ls
       2. if too many arguments are passed into ls

  2. mkdir : creates a directory

     • -v : verbose - informs that a directory has been created

     • -p : creates parent directories as well

     • Corner Cases Defended

       1. if an operand is missing, e.g. filename after mkdir
       2. if a directory cannot be created because it already exists

  3. rm : removes a file

     • -i : prompts before removal

     • -v : informs after removal

     • Corner Cases Defended

       1. if the user tries to remove a file that does not exist
       2. if there is a missing operand
       3. if an invalid option is passed into rm

  4. cat : prints the contents of a file

     • -n : prints line numbers

     • -E : prints $ at the end of each line

     • Corner Cases Defended

       1. if the user tries to open a file or directory that doesn't exist
       2. if the user passes an invalid option

  5. date : prints the current date and time

     • -u : time in gmt

     • -R : time in rfc 5322 format

     • Corner Cases Defended

       1. invalid option
       2. invalid command

• internal commands supported:

  1. cd : changes the current working directory

     • - : goes to previous working directory

     • -P : symbolic link components shall be resolved before dot-dot components are processed

     • -L : symbolic link components shall not be resolved before dot-dot components are processed

     • --help: prints help

     • Corner Cases Defended

       1. passes an invalid option
       2. passes an invalid number of arguments

  2. pwd : prints the current working directory

     • -L : follow symlinks

     • -P : dont follow symlinks

     • Corner Cases Defended

       1. cannot read current directory
       2. invalid option

  3. echo : prints the arguments passed to it

     • --help : print help

     • -n : removes newline

     • Corner Cases Defended

       1. invalid option
       2. invalid command

  4. exit :

     • exits the shell

Use of fork() and exec()

• used fork() and exec() calls
• fork() creates a new process by copying the current running one
• exec() replaces the new, child process with the required process

Use of pthread_create and system in commands involving "&t"

• pthread_create() creates a new thread to run the command
• the command needs to be of the form "command&t -option"
• for example, "ls&t -1"