Minishell

This is the first group project in the 42 Core curriculum. In this project, we created our simple shell.

Requirements

Here are the functionalities we implemented:

• 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).

• Handle ’ (single quote).

• Handle " (double quote).

• Implement redirections: ◦ < should redirect input. ◦ > should redirect output. ◦ << 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.

• Implement pipes.

• Handle environment variables.

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

• Handle ctrl-C, ctrl-D, and ctrl-\ which should behave like in bash.

• Builtins: ◦ echo with option -n ◦ cd with only a relative or absolute path ◦ pwd with no options ◦ export with no options ◦ unset with no options ◦ env with no options or arguments ◦ exit with no options

Implementation

The project was split into 2 parts: parsing and execution Parsing:

• Tokenizer and lexer: We get the command and create a linked list of tokens. Each token will have a type based on its value.
• Expander: Expand the environment variables to their values, remove quotes, and expand $? to the last exit status.
• Create command list: We create a linked list of all the commands. Each command will contain
  • The command to execute
  • A linked list of input redirections (each with a type that indicates < or <<)
  • A linked list of output redirections (each with a type that indicates > or >>)
  • A pointer to the next command

  • Once this is done, we can do the execution part and execute each command.

How to run

make

./minishell

To run and check for memory leaks, execute the following:

valgrind --suppressions=readline.supp --leak-check=full --show-leak-kinds=all ./minishell

Then type any command, as if you were in a bash shell and have fun!