2021-04-05 - SpaceLaunch space program
-------------------------------------------------------------------
A while ago i was playing around with the Spacelaunch program on
this ~team server. The sl command is a really nice little program
which allows users to shoot rockets up over the terminal screen.
The rockets consist of small rocket-sections made by all the other
users on the server. And users are invited of course to also draw
their own section.
This neat program is made by cmccabe for the Zaibatsu server, and
can be found over here [0]. It is apparently based on an old 'steam
locomotive' Unix prank (which i assumed is called after mistyping
the ls command)
Anyhow, of course i started designing the most beautiful rocket
section i could think of:
======================
| # # ## ### |
| ## # # # # # |
| # ## # # ### |
| # # ## # |
\_________________ /
\ ~TEAM /
| o o o o o o o|
( TO GOPHER )
\ SPACE /
`----------`
==| [ NN ] |==
==|====[ OO ]====+==
==| [ PP ] |==
/~~~~~~~~\
/ ____ \
/ | | \
( |(oo)|__hey!
./ |m()m| \.
/ \
| o o O O O o o|
|====================|
After drawing this rocket section, i tested my .vroom file with the
'sl -t' command, but unfortunately, it seemed to fail every time :(
The program would give a fairly "cryptic" output saying that my
file wouldn't pass the requirements:
nop:~$./sl.sh -t
==========================================================
Testing your .vroom file...
FAIL! Your .vroom file does not meet one or more of the
following requirements:
* Each line in the .vroom file must be exactly 22
characters in length.
* The .vroom file may contain no more than 22 lines.
==========================================================
I double, tripple and quadruple-checked my .vroom file, but
couldn't see why it wouldn't conform to the requirements. It had 22
lines of exactly 22 characters wide.
Strangely enough, when shooting up rockets in the air with the 'sl'
command, my rocket section passed by occasionally as well. So my
rocket section was working, but was reported to fail by
the 'sl -t' function. So something strange was happending.
To check it out i downloaded the spacelaunch program [0], and found
out the whole program was actually a masterfully written
bash-script by cmccabe. (I kinda expected a c program or so)
I've never really written bash scripts, so i didn't know you could
all these things with bash even. So after some figuring out how
everything works, i found that the error was caused by a 'read'
command, which was throwing away the leading spaces in my .vroom
lines.
This is apparently default behaviour of the read program. If i
input a string with many leading spaces, the spaces get trimmed
away by the read program.
==============================
nop:~$ read; echo ${REPLY}
<- Leading spaces
<- Leading spaces
=============================
But somehow, this only happened when the 'sl -t' function was run,
and not when the 'sl' program was run.
Turns out, this was caused by the IFS (Input File Seperator) which
was not (un)set for the portion of the script that ran the 'sl -t'
function.
Normally the IFS is set to <space><tab><newline> or so, but for
this script it has to be set to blank '', for everything to
function properly. This was done for the function that launched the
rocket, but not for the function that checked the rocket.
While i was testing this, i added debug lines to the function that
tested the .vroom files; VALIDATE_VROOM().
As i found the 'sl -t' output to be rather cryptic earlier, (it
didn't say exactly what was wrong with my rocket section), i
decided to use my debug lines and add a 'verbose' mode to the
function.
This way, the 'sl -t' function would give a lot more verbose
information on what is wrong with a .vroom file. Which is helpful
for people like me... :)
So now in the modified program, the output looks like this:
nop:~$./sl.sh -t
==========================================================
Performing rocket section diagnostics...
Analyzing your .vroom file...
01:====================== Width:22 chars. PASS
02:| # # ## ### | Width:22 chars. PASS
03:| ## # # # # # | Width:22 chars. PASS
04:| # ## # # ### | Width:22 chars. PASS
05:| # # ## # | Width:22 chars. PASS
06: \_________________ / Width:22 chars. PASS
07: \ ~TEAM / Width:22 chars. PASS
08: | o o o o o o o| Width:21 chars. FAIL
09: ( TO GOPHER ) Width:22 chars. PASS
10: \ SPACE / Width:22 chars. PASS
11: `----------` Width:22 chars. PASS
12:==| [ NN ] |== Width:22 chars. PASS
13:==|====[ OO ]====+== Width:22 chars. PASS
14:==| [ PP ] |== Width:22 chars. PASS
15: /~~~~~~~~\ Width:22 chars. PASS
16: / ____ \ Width:22 chars. PASS
17: / | | \ Width:22 chars. PASS
18: ( |(oo)|__hey! Width:22 chars. PASS
19: ./ |m()m| \. Width:22 chars. PASS
20:/ \ Width:22 chars. PASS
21:| o o O O O o o| Width:22 chars. PASS
22:|====================| Width:22 chars. PASS
==========================================================
Rocket section height: 22 lines. PASS
FAIL! Your .vroom file does not meet one or more of the
following requirements:
* Each line in the .vroom file must be exactly 22
characters in length.
* The .vroom file may contain no more than 22 lines.
==========================================================
This way, you can see exactly on which line the .vroom file fails
(in the above example on line 08, due to a too small width)
Hopefully, with the small IFS bug fixed, and the improved
diagnostics output, even more rockets will be launched over the
console with cmccabe's awesome script.
I will forward the modified script to cmccabe for review. I've
never modified bash scripts before, so it's very possible i've
missed some things when changing the script.
The modified sl.sh script can also be found over at [1] for the
time being.
[0]
gopher://zaibatsu.circumlunar.space/1/software/spacelaunch
[1]
gopher://tilde.team/0/~nop/misc/sl.txt
