A unix shell.

42sh run like other basic shells like sh or csh.
It includes the following builtins :
exit.
cd [-LP].
echo.
history [-cdanrwps].
read [-r].
export [-p].
set.
unset.
setenv.
unsetenv.
env [-iu].

It also includes several functionalities :

The semicolon and conditons :

% mkdir repertory ; cd repertory ; pwd
/.../repertory
% test 10 -gt 2 && echo TRUE ; test 2 -gt 10 || echo FALSE
TRUE
FALSE

The pipe :

% echo test | tr e E | cat -e
tEst$

The redirection :

% echo A > file ; echo B >> file ; cat < file
A
B

The heredoc :

% cat << eof

test
eof

test

The file descriptors :

% touch foo ; touch bar ; rm foo ; ls foo bar 2>&-
bar
% touch foo ; touch bar ; rm foo ; ls foo bar 2>&1 | cat -e
ls: foo: No such file or directory$
bar$
% echo TEST 6>file 1>&6 ; cat 8<file 0<&8
TEST

The globing :

% touch a2 aa2 aa1 bb1 b2 cc2 ; echo [ab]?[2]
aa2
% touch a2 aa2 aa1 bb1 b2 cc2 ; echo *a*
aa2 a2 aa1

The subshell :

% (echo A ; echo B ; echo C) | cat -e
A$
B$
C$

The backquotes :

% `echo touch file` ; ls -l file
-rw-r--r-- 1 mdugot 2015_paris 0 Jul 1 14:01 file

The quotes and backslash :

% echo "';'" ; echo '"|"' ; echo \*
';'
"|"
*

The exclamation mark :

%echo 2
%echo 1
%!e
echo 1
1
%!-2
echo 2
2

And a line editor with keyboard shortcut :
LEFT-RIGHT : move the cursor.
UP-DOWN : can browse through the history.
TAB : autocompletion.
Ctrl-b : go one world back.
Ctrl-n : go to the next world.
Ctrl-l : go down to the next line.
Ctrl-k : go up to the previous line.