Just 5 different applications that leveragae various POSIX syscalls to do things.
just echoes back input to the stdout.
find a specific substring within all files recursively starting at the input path while taking care of symlinks and stuff.
a unix shell that can fork and exec programs with IO redirection using unnamed pipes, backgrounding and foregrounding of processes and singnal handling
as well as multi-processes matrix multiplication implemented using shared memory
A basic ptrace based debugger thaat can set breakpoints based on line numbers leveraging libdwarf.