The Nut Shell is a framework for creating interactive command line tutorials, inspired by text adventures. It can be used to teach system shells, interpreted programming languages, or subtopics, like specific command line tools or concepts.
To start a Nut Shell tutorial, use nutsh run LESSON_DIR. To test a tutorial for proper function, use nutsh test LESSON_DIR.
Do you know the old joke "How do you put an elephant into a fridge?"
"Open the fridge, put in the elephant, and close the door". Try it, we
delivered a fresh elephant into your kitchen!
$ cd kitchen
$ ls
elephant fridge/
$ mv elephant fridge
[The elephant does not fit into the fridge]
Oh, it doesn't seem to be that easy. Can you find out how big the file
is? The man page of ls will help you!
$ ls
elephant fridge/
$ man ls
[Display of the man page, skipped here]
$ ls -l
-rw------- 1 seb users 10485760 27. Okt 22:25 elephant
drwx------ 2 seb users 4096 27. Okt 22:25 fridge
Okay, about ten million bytes. ls has the option -h to display that in
a more comprehensible order of magnitude.
$ ls -sh
10M elephant 4.0K fridge
10 megabytes? Indeed, the fridge isn't that large.
We have to make the elephant smaller. There are several ways to
compress files - one of the most common under Linux is gzip.
Compress the elephant with that program and look at it's size again.
$ gzip -f elephant
$ ls -sh
3.4M elephant.gz 4.0K fridge
That sounds much better.
Because that went so well, we've delivered a second elephant to the
hallway. Get it into the kitchen and and compress it, this time with
bzip2. How large is the file this time?
$ ls ..
bedroom/ elephant2 kitchen/ livingroom/
$ cp ../elephant2 .
$ bzip2 -f elephant2
$ ls -sh
1.9M elephant2.bz2 3.4M elephant.gz 4.0K fridge
The bzip2 compression algorithm takes more time, but creates smaller
files.
The two compressed elephants now fit in the fridge comfortably! (Hint:
Using wildcards you can move both files at once!)
$ mv elephant* fridge
These commands only compress single files. To compress a folder, you
have to combine it and its contents to a single file, you can do that
with tar -c -f name_of_the_archive.tar folder.
-c stands for "create", -f for the name of the resulting file. tar is
short for "tape archive" originates from the good old times, when
magnetic tapes were used to store files.
Please combine the fridge to fridge.tar.
$ tar -c -f fridge.tar fridge
The compression commands replace the original file, but tar
leaves the source folder intact. Please delete the original fridge.
$ rm -rf fridge
Good, and now compress the so-called "tar ball" with a compression
method of your choice.
$ gzip fridge.tar
You can now pick up the compressed fridge with the compressed
elephants, put it in your pocket and take it with you. :-)
And eventually, we want to get the elephants back. Reverse your steps
and put both elephants back into the kitchen.
Use the commands gunzip and bunzip2, as well as tar with the arguments
-x -f name_of_the_archive.tar (-x means "extract").
$ tar xzf fridge.tar.gz
$ gunzip fridge/elephant.gz
[The elephant does not fit into the fridge]
$ bunzip2 fridge/elephant2.bz2
[The elephant does not fit into the fridge]
Enjoy your meal! When you're ready to complete the lesson, say "done"!
$ echo done
done
The Nut Shell comes with a domain specific language, that can be used to write tutorial lessons. To give you an idea of nutsh's syntax, here's the source code for the above lesson. First we define some macros:
// create a folder as an environment for the lesson
def make_home {
run(`ROOT="$HOME"/.nutsh`)
run(`mkdir -p "$ROOT"`)
run(`cd "$ROOT"`)
run(`mkdir -p kitchen bedroom livingroom`)
}
// return the exit code of the last command
def exit_code {
return(run("echo $?"))
}
// check a conditional expression using bash's "[[ ]]" syntax
def test(condition) {
run(cmd)
run("[[ "+condition+" ]]")
return(exit_code == "0")
}
// check whether the directory 'd' exists
def dir(d) {
return(test("-d \""+d+"\""))
}
// check whether the file 'f' exists
def file(f) {
return(test("-f \""+f+"\""))
}
// was the last command "echo done" or "echo ready"?
def done {
return(command =~ `echo\s+(done|ready)`)
}
And here's the actual lesson:
make_home
// create a file that contains 10 MiB of ascending numbers
run(`seq 1 2000000 | tr -d '\n' | head -c $((1024*1024*10)) >
"$ROOT/kitchen/elephant"`)
"Do you know the old joke \"How do you put an elephant into a fridge?\""
"\"Open the fridge, put in the elephant, and close the door\". Try it, we
delivered a fresh elephant into your kitchen!"
// check whether there's an elephant (with suffix 'n') in the fridge
def elephant_in_fridge(n) {
return(file(`"$ROOT/kitchen/fridge/elephant"`+n))
}
// when there's an elephant in the fridge, show an error and remove it
def stop_elephant(n) {
if elephant_in_fridge(n) {
"[The elephant does not fit into the fridge]"
run(`mv "$ROOT/kitchen/fridge/elephant`+n+
`" "$ROOT/kitchen/elephant"`+n)
}
}
prompt {
if elephant_in_fridge("") {
stop_elephant("")
expect("cd kitchen; mv elephant fridge")
break
}
}
// using a nesting statement, disallow elephants in the fridge for the rest
// of the tutorial
stop_elephant(""), stop_elephant("2") {
"Oh, it doesn't seem to be that easy. Can you find out how big the file
is? The manpage of `ls` will help you!"
prompt {
if output =~ "10M" {
expect("ls -sh")
"10 megabytes? Indeed, the fridge isn't that large."
break
}
if output =~ "10240" {
expect("ls -s")
"Okay, about ten thousand kilobytes. `ls` has the option `-h` to
display that in a more comprehensible order of magnitude."
}
if output =~ "10485760" {
expect("ls -l")
"Okay, about ten million bytes. `ls` has the option `-h` to display
that in a more comprehensible order of magnitude."
}
}
"We have to make the elephant smaller. There are several ways to
compress files - one of the most common under Linux is `gzip`. Compress
the elephant with that program and look at it's size again."
prompt {
if file(`"$ROOT/kitchen/elephant.gz"`) {
// depending on the locale, the decimal mark can be a comma or a dot
if output =~ `\d[.,]\dM` {
expect("gzip -f elephant; ls -sh")
break
}
}
}
"That sounds much better."
"Because that went so well, we've delivered a second elephant to the
hallway. Get it into the kitchen and compress it, this time with
`bzip2`. How large is the file this time?"
run(`seq 1 2000000 | tr -d '\n' | head -c $((1024*1024*10)) >
"$ROOT/elephant2"`)
prompt {
if file(`"$ROOT/kitchen/elephant2.bz2"`) {
if output =~ `\d[.,]\dM` {
expect("cp ../elephant2 .; bzip2 -f elephant2; ls -sh")
break
}
}
}
"The bzip2 compression algorithm takes more time, but creates smaller
files."
"The two compressed elephants now fit in the fridge comfortably!
(Hint: Using wildcards you can move both files at once!)"
prompt {
if file(`"$ROOT/kitchen/fridge/elephant.gz"`) &&
file(`"$ROOT/kitchen/fridge/elephant2.bz2"`) {
expect(`mv elephant* fridge`)
break
}
}
"These commands only compress single files. To compress a folder, you
have to combine it and its contents to a single file, you can do that
with `tar -c -f name_of_the_archive.tar folder`."
"`-c` stands for \"create\", `-f` for the name of the resulting file.
`tar` is short for \"tape archive\" originates from the good old times,
when magnetic tapes were used to store files."
"Please combine the fridge to `fridge.tar`."
prompt {
if file(`"$ROOT/kitchen/fridge.tar"`) {
expect("tar -c -f fridge.tar fridge")
break
}
}
"The compression commands replace the original file, but `tar` leaves
the source folder intact. Please delete the original fridge."
prompt {
if ! dir(`"$ROOT/kitchen/fridge"`) {
expect("rm -rf fridge")
break
}
}
"Good, and now compress the so-called \"tar ball\" with a compression
method of your choice."
prompt {
if file(`"$ROOT/kitchen/fridge.tar.gz"`) ||
file(`"$ROOT/kitchen/fridge.tar.bz2"`) {
expect("gzip fridge.tar")
break
}
}
"You can now pick up the compressed fridge with the compressed elephants,
put it in your pocket and take it with you. :-)"
"And eventually, we want to get the elephants back. Reverse your steps
and put both elephants back into the kitchen."
"Use the commands `gunzip` and `bunzip2`, as well as `tar` with the
arguments `-x -f name_of_the_archive.tar` (`-x` means \"extract\")."
prompt {
if file(`"$ROOT/kitchen/elephant"`) &&
file(`"$ROOT/kitchen/elephant2"`) {
expect("tar xzf fridge.tar.gz; gunzip fridge/elephant.gz;
bunzip2 fridge/elephant2.bz2")
break
}
}
}
"Enjoy your meal! When you're ready to complete the lesson, say \"done\"!"
prompt {
if done {
expect("echo done")
break
}
}