wish

A command line interpreter that runs in linux environment.

compilation make wish remove compiled files make clean

Supported Mode:

• Interactive Mode
• Batch Mode
  • usage ./wish batch.txt

supported built-in commands:

• path change path, path will be overwriten each time. When empty shell is provided, shell can only execute built-in commands
• history x, show x lines of user commands history
• exit exit the shell
• cd change current directory

Otherwise unspecified, shell will try to find binary executable in current path exhaustively.

History will report error in following cases:

• more than 1 arguments

• the first argument is not a valid number (+,-,. can only appear once; +,- can only appear at begining, . can only appear in middle. Any other characters results in invalid number)

• In the following cases: history will print all lines recorded since the program starts

  • the first argument exceeds number of lines of current record
  • the first argument exceeds maximum buffer size for current log(the maximum is mannually set to be 2048) If input number <= 0, history will do nothing.

• redirection of builtin commands are supported.

• piping of builtin commands are not supported.

• for piping and redirection: When user input commands like: "x>x" "x|x" error will be thrown when: left x is empty or space right x is empty or space both left x and right x is empty or space for redirction, addtionally, multiple files after > will be regarded as errors

• for piping: when both left x and right x are not empty: if BOTH left x and right x excutables are not found in current search path then two error will be reported if left x is found in current search path AND right x is not found it will behave like normal shell except that one error will be reported and no output will appear on stdout. if left x and right x are BOTH found in current search path output to stdout and stderr of left x will be piped to stdin of right x finally, if left x is not found AND right x is found, the error should be redirected to right x (Not supported, simply skip right side instruction).