Three things scripts wanted, and they are one thing: a machine that can
have a face.
/System/Boot/startup.sh runs before anybody can type. Every way of reaching
the prompt for the first time goes through it, including the one where
there is no disk - in which case there is nothing to find and nothing is
said. A MISSING one is ordinary and silent, because a clean install has
none and a machine that complained every boot about a file nobody wrote
would be teaching its owner to ignore it. One that is THERE and does not
begin with #! is the other case entirely: somebody meant that to run.
#quiet stops each line being echoed, #loud puts it back. The prompt and the
echo go together, because together they are what makes a script look like
typing, so a quiet script gets neither and what it prints is all that
appears. A nested script inherits quiet - a build that asked for it meant
its helpers too - and gets its own setting back when the helper returns.
Anything else beginning with # is handed to the shell, which does not know
it and stops the script, because a script that asked for something this
shell cannot do should not carry on as though it had been given it.
clear empties the screen, which the console has been able to do since
before there was a screen to do it on.
THE PROMPT IS NOW SAID BY WHOEVER SUPPLIES THE LINE. It used to be said at
the top of the loop, which is a decision made before the line is read and
an answer not known until after - and it was wrong at both ends. #quiet is
itself a line, so its prompt went out before anything knew to stay silent;
and the line after a quiet script's last one comes from the console, having
already been denied one. Off by exactly one line in opposite directions. A
first attempt at this remembered whether the prompt had been skipped, which
worked and was a flag standing in for a structure. The monitor's assembler
prints a prompt of its own, so it reads through shellReadRaw, which is the
same source without one.
One admission. Handing the console its prompt back when a quiet script
ended was a real fix when I wrote it and stopped being one an hour later,
because the restructure above means the console's own path prompts whatever
the flag holds. The comment claimed it fixed something. Breaking it on
purpose changed nothing, which is how that was found, and it is now a
comment saying so instead of a line pretending to work.
The startup fixture ends QUIET on purpose: nothing puts the flag back when
the outermost script finishes, so a script ending #loud would have tested
the easy half.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW
Say.sbx has printed words since long before there were scripts, and is the
wrong shape for one. It is a program: it has to be found on the disk,
loaded and started, it prefixes what it was told with "it says:", and the
system prints "finished" after it. Three lines of noise around one line of
narration, and a load off the disk to produce them.
echo is a command, so it costs a comparison. With nothing after it, a blank
line - which is what anybody expects and is worth having to space a long
script out.
Not called "say", although that is the better word. Built-in commands are
tried before the disk and always win, so a built-in say would shadow Say.sbx
and quietly change what every existing script and test meant by it.
Also puts "do" in the help, which the commit that added it forgot, and
splits the help text: the new lines pushed it over the assembler's 255
character limit for one string. That failure was hidden for a few minutes
by a 'make' whose errors were going to /dev/null - the build kept the disk
it already had, and the machine cheerfully reported "I do not know: echo"
from a system assembled before echo existed.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW
The prompt is the working directory's path, worked out each time by walking
the chain of parents up to the root. The names arrive deepest first, so
they are written backwards from the end of a 127 byte buffer - and nothing
bounded that walk.
Nothing bounds the depth either. A path given to one operation is capped at
95 characters and a 22 character name, but "mkdir a" and "cd a" are each
far inside that and can be repeated forever. Six directories of 22
characters is 132 characters of path, and at that point the walk wrote down
past the front of CwdText and into what the assembler had laid out below
it: the shell's own command names. ExitName sits five bytes under, so the
word "exit" went first and the shell stopped recognising the command for
leaving. Measured, not deduced: fine at five levels, gone at six.
The walk now counts the room it has left, byte by byte, and stops. What is
already written is the DEEP end of the path, which is the end worth
showing, so it is cut at the front and three dots say so - out of three
bytes held back from the count, so there is always somewhere to put them.
Twenty levels deep the prompt shows the last five and every command still
works.
cosmosDeep records that, and records it by running help, cd and exit from
down there rather than by looking at the prompt: a wrong prompt is
cosmetic, and this was writing into other variables. It fails with the
bound removed. The tree is built by SplitDisk because a path that long
cannot be given to mkdir in one piece - which is the same fact that makes
the depth unbounded.
The three path limits are written down in the README now, including which
one actually binds. The other two do not: the longest path on a full
install is 21 characters.
AnachronautandClaude Opus 5