What is 42sh

42sh is a bash-styled shell project completely written from scratch in C with very limited access to libraries and tools.

The learning goals of the project:

• Learn a lot more about the inner workings of the UNIX system.
• Learn about the different type of shell implementations.
• Learn what a lexer is and how to write it.
• Learn what a parser is and how to write it.
• Learn how to write nice and clean code.
• Learn how process execution work.
• Learn some porsix features.
• To create a stable and complete UNIX shell.

Functionality

1. Error monitoring without using errno.
2. Prompt display.
3. Complete management of input.
4. (Multiline) line edition.
5. Redirection with the following operators:
   • >
   • >>
   • <
   • <<
   • >&
   • <&
6. Control operators:
   • |
   • ||
   • &&
   • ;
   • &
7. Quoting managment ", ', and \ or inhibitors.
8. Basic parameter expansion and additional parameter formats:
   • Word expansion performs by POSIX
   • ~
   • ${parameter:-word}
   • ${parameter:=word}
   • ${parameter:?word}
   • ${parameter:+word}
   • ${#parameter}
   • ${parameter%}
   • ${parameter%%}
   • ${parameter#}
   • ${parameter##}
9. Command history:
   • !!
   • !word
   • !number
   • !-number
   • Saving to a file so that it can be used over several sessions
   • Built-in fc (all POSIX options)
   • Incremental search in the history with CTRL-R
10. Autocomplete.
11. Builtins:
    • echo
    • cd
    • env
    • export
    • setenv
    • unsetenv
    • exit
    • type
12. Pattern matching (globing): *, ?, [], ! and the caracters intervals with \ (backslash).
13. Control or command substitution: $().
14. Alias management via built-ins alias and unalias.
15. A hash table and built-in hash to interact with it.
16. Monitoring of intern shell variables.
17. Job control monitoring, with buitl-ins jobs, fg, bg and the & operator.

Installing and running 42sh

Install:

git clone https://github.com/Tsorion9/42sh.git
make && make clean

Run:

./42sh

Authors

Volkov Ilya, Alex Buyanov, Golovizin Anton, Artur Tsorionov