Minishell

Minishell is a command-line interpreter designed to mimic bash's behavior. It is built from scratch using C.

Parsing architecture relies on an Abstract Syntax Tree (AST) and shift-reduce parsing algorithm.

Features

Command execution:

• Display a prompt when waiting for a new command.
• Have a working history.
• Search and launch the right executable (based on the PATH variable or using a relative or an absolute path).
• Not interpret unclosed quotes or special characters which are not required by the subject such as \ (backslash) or ; (semicolon).
• Support custom built-in commands:
  • cd with no options
  • pwd with no options
  • echo with option -n
  • export with no options
  • unset with no options
  • env with no options or arguments
  • exit with no options

Operators

• Implement pipes (| character). The output of each command in the pipeline is connected to the input of the next command via a pipe.
• Implement redirections:
  • < should redirect input.
  • > should redirect output.
  • << should implement heredocs. It should be given a delimiter, then read the input until a line containing the delimiter is seen. However, it doesn’t have to update the history!
  • >> should redirect output in append mode.

Shell-specific behaviors

• Handle environment variables ($ followed by a sequence of characters) which should expand to their values.

• Handle $? which should expand to the exit status of the most recently executed foreground pipeline.

• Handle ’ (single quote) which should prevent the shell from interpreting the meta- characters in the quoted sequence.

• Handle " (double quote) which should prevent the shell from interpreting the meta- characters in the quoted sequence except for $ (dollar sign).

• Signal Handling: Handle ctrl-C, ctrl-D and ctrl-\ which should behave like in bash. In interactive mode:

  • ctrl-C displays a new prompt on a new line.
  • ctrl-D exits the shell.
  • ctrl-\ does nothing.