M-Evans / rshell

UCR CS100 Project

rshell

UCR CS100 Project

What is rshell?

• a basic shell for unix-based systems
• not finished
• very limited
• contains a custom version of ls.

Features (rshell)

• Command chaining with ||, &&, and ;
• Executes commands
• Comments are not interpreted
• Handles EOF being sent
• Handles the exit command
• No memory leaks! (that I know of)
• Says hello and goodbye

Bugs (rshell)

• If a syntax error is detected, no chained commands before the syntax error will be executed. (unlike in other shells where they can sometimes be recovered from)
• Semicolons between && and || connectors and their corresponding commands are ignored. If there is no command between connectors or the end of the line, then it's still a syntax error. Also, if the semicolon connects to the && or || operators, then the syntax error is still thrown. Only doesn't work for a small portion of the cases.
• It does not have the capability to prepare food

Features (ls)

• color!
• accepts -a as a parameter (lists hidden files)
• accepts -l as a parameter (lists lots of info about the files and directories, as well as a cumulative block count of the things printed)
• accepts -R as a parameter (lists the contents of directories and their directories)
• accepts any number of files/directories to print
• parameters and flags are accepted in any order

Bugs (ls)

• compared to the GNU ls, I sort things differently. I sort everything alphabetically including the preceding periods. GNU ls sorts everything based on the first letter, ignoring preceding periods
• it does not gracefully handle improper flags - they cause fatal errors

Features (signals)

• ignores SIGINT
  • SIGINT is recieved by child
  • without children, SIGINT does not do anything
  • handling of SIGINT is child-dependent
• ignores SIGTSTP
  • SIGTSTP is received by child
  • If the child goes into the background, it is remembered
  • it can then be foregrounded or backgrounded as you please
• cd is implemented
• reads PATH to figure out which executable to run

Bugs (signals)

• SIGINT
  • running rshell inside of rshell and sending SIGINT causes the prompt to be printed twice
• SIGTSTP / process handling
  • when backgrouding (bg) a process that requires input (such as cat), they run simultaneously and seem to fight for input. In the case of cat, the first thing typed goes to cat and the second thing typed goes to rshell.
• cd
  • lacks many features
• PATH
  • The command to execute is appended to each path and then checked for existence, so subfolders and executables within them may be executed