Bash programing isue

[ethan26]

Hi people, i am new to this form as this is my first post on this fourm or any other fourm for that matter but i find fourms useful when learning new programing launguages and so to get to the problem i am having:
I am atempting to write a code that will echo a random number untill a key is pressed. When a key is pressed it should echo on the same line DONT TOUCH THE KEYBOARD. its not going well. so far i have this:

#!/bin/bash
while true; do
while true; do echo -n $RANDOM; & read -n1 -s VAR
echo "DONT TOUCH THE KEYBOARD"
to break down what i was trying to do the while true; do was supost to echo $RANDOM forever untill a key was pressed then the & was supost to execute the two commands (do echo -n $RANDOM and read -n1 -s VAR) at the same time. If any key was pressed the read command would break and it would echo DONT TOUCH THE KEYBOARD. now that i look at the code again i realize that i should have added the -n option to the echo command and made a loop around all of it but if you guys could help me out i would really apriciate that.
Thanks

[bardo2]

in my own understanding, the choice to use bash for that purpose is a weird one. Bash is not a programming language, it is a shell scripting language, best used to glue a couple of commands into a script.

That said, first thing to investigate/learn, i'd suggest the trap command, which prevents unexpected interruption of the script. i frequently use it to clean up after something got interrupted, but you can also just ignore events.

Next, read (a.k.a. readline) doesnt see keypresses, only waiting for a line terminator. I am certain, there will be some alternative too, but let's be clear: nothing is ever going make bash a good choice for the purpose. If you were my son, i'd recommend to have a look at python, which can be easy as "BASIC" used to be, yet modern (object-oriented), versatile (nothing you couldnt do with it), and very many libraries around to make your task easier by incorporating other peoples work.

just my 2 cents

[ethan26]

Thanks for your input. I have a freind who knows python and im shure he could help me to learn it. But does python require dowloading somthine special to run the program because I want to avoid that at all costs. Wich is why I havent learned java. so what would you sugest bash for?
thanks again!

[bardo2]

on most 'nix standard installs (you didnt mention yours), there is some version of python already installed, especially in ubuntu, because parts of ubuntu are effectively written in python. You can check by issuing

python -V
from a commandline

[ethan26]

I just checked the command you gave me and i got

*****@*****-E6610:~$ python -V
Python 2.7.6
wich means that i do have python installed! :KS
also my computer is runing ubuntu 14.04 LTS
and what is the extention for puthon script (the equivelent of .sh to be clear
and how would you write this type of script in python.
thanks

[bardo2]

ask google, it turned up plenty of examples

[ethan26]

ok

[ethan26]

I like the input that have given me but you still did not answer my original question or provide any help about the code that i provided. i do apriciate you taking your time and responding but I was really looking for help with bash not python.
thanks, and happy easter!:p

[bardo2]

??? read again my post #2

edit: i use keywords "bash keypress" and find answers right away, you should be more involved. complaining wont help

[ethan26]

sorry, didnt understand what you were saying at the time. i thought you were giving commands in python to test.

[bardo2]

it's ok.
again, if you were my son, i'd say: "you seem to be interested in playing a song. That is nice. But up till now, you are using the drums only. But maybe, to learn the piano is too difficult on your own. I understand that. Go get a teacher (which i am not)."

[ethan26]

coincidentely i do play the piano

[bardo2]

great! :KS

[ethan26]

im going to leave this thread open as i am open to sugestions

[bardo2]

very happy to have seen this: http://ubuntuforums.org/showthread.php?t=2272247
indicating, you found an excellent way to make progress.

Well done!

[steeldriver]

Not sure exactly what you're looking for, but based on your attempt to use a while loop in your original post, perhaps something like this?



#!/bin/bash

msg='DON'\''T TOUCH THE KEYBOARD'

while :
do
if read -s -t1 -n1 input; then
printf "%s\r" "$msg"
else
printf "%-*s\r" "${#msg}" "$RANDOM"
fi
done


I'll leave you to study it - you should find



help read

help printf

man 3 printf


useful.

[ethan26]

Thanks this is basicly what i was hoping for however i wanted th output to look somthing like


64132311832876431790721271176614429140191096123011 96512090212827116188998228534252882011272632618401 11652952147591000226889932317115224481215473525
62919020794481181241030289527021696147772862225900 28929937943121090245022290228629106173051018940245 39221142530081603065895892963032734662028400356
23051682629401203131305711094311031693927742239211 82182979111885144912709321888288672033318275138128 22717657286701604191249820394817409192376279682
96662962261754098133731462441962915229783167121529 62459113965281026241311803233797986608226342986826 16517085201481791818052200931865921591225192891
75966119692350313948139212868030233242683731437200 87161262157114830309282517123200308699015550989726 97750341986712398250828062498184892710124070101
67135251776716286233152050603307991675342481394820 25111777576588831529DONT TOUCH THE KEYBOARD832363218095122191992151981584725026929422 935166
56587726518313331704022420227042055541101708321788 16059579721633924512873134919278604011193770321837 27890167932455521162992718138203605942690532137
31423126623181212922168712591798341012313475270273 29171301328619229323236672020816464272901928332033 12461241821330238612490319460265171579091023135
32705621973146497905105322725101541200216209803421 38263337681047621739200102217817123271591206659823 14171041223016064300665342167722022210802574311
But thank you so much. i am doing homework but when i am done i will tweak the code and post it back here
thank you again. this forum is so helpful!
and to (http://ubuntuforums.org/member.php?u=1975410)bardo2 (http://ubuntuforums.org/member.php?u=1975410):
i am so glad you endorse my efort to engage the commutiy to help me learn python. in all honisty i was hesitant to post that tread as i thought that you would get mad if you saw it.
Thanks to all and happy easter!:p

[ethan26]

ok so i edited it and got this

#!/bin/bash

msg='DON'\''T TOUCH THE KEYBOARD'

while :
do
if read -s -t1 -n1 input; then
echo "$msg"
else
echo -n "$RANDOM"
fi
done
but it gives me this:

139721741720565DON'T TOUCH THE KEYBOARD
15329451820933107308571176093655807164332078772079 110032224732423252521577462171526411493160166
if you could sho me how to make it echo the random number directly after $msg that would be terific!
except its a litte slow, lol. i need help with that too.
thanks in advance!

[steeldriver]

Did you read any of the documentation I suggested?

Obviously I misunderstood what you meant by "on the same line" - you seem to have discovered the 'echo' command's -n option (although you could have simply removed the '\r' carriage return from the printfs), so think about how that affects your output

For the speed, I really do suggest you read the documentation for the 'read' built-in ('help read' - or 'man bash' if you want more detail) and make sure you understand the usage of its command line options

[ethan26]

lol! i completely missed that! then when i tried to edit the code and took out the -t1 opyion it didnt work but i figured it out:

#!/bin/bash

while :
do
if read -t0.02 -s -n1 input; then
echo -n "D"
sleep 0.02
echo -n "O"
sleep 0.02
echo -n "N"
sleep 0.02
echo -n "T"
sleep 0.02
echo -n " "
sleep 0.02
echo -n "T"
sleep 0.02
echo -n "O"
sleep 0.02
echo -n "U"
sleep 0.02
echo -n "C"
sleep 0.02
echo -n "H"
sleep 0.02
echo -n " "
sleep 0.02
echo -n "T"
sleep 0.02
echo -n "H"
sleep 0.02
echo -n "E"
sleep 0.02
echo -n " "
sleep 0.02
echo -n "K"
sleep 0.02
echo -n "E"
sleep 0.02
echo -n "Y"
sleep 0.02
echo -n "B"
sleep 0.02
echo -n "O"
sleep 0.02
echo -n "A"
sleep 0.02
echo -n "R"
sleep 0.02
echo -n "D"
else
echo -n "$RANDOM"
fi
done
i figured i didnt need the hasle of the printf command and the apostraphe as i saw they would cause me trouble in the future
thank you all so much and i will leave this thread open for sugestions

[ethan26]

Update:
i edited the code to make it look for the package beep and install it if need be and play fun beep sounds and i got this:

#!/bin/bash
echo "some of the commands used in this script reqire the sudo command witch requiers "$USER"s password"
PKG_OK=$(dpkg-query -W --showformat='${Status}\n' beep|grep "install ok installed")
echo Checking for stuff: $PKG_OK
if [ "" == "$PKG_OK" ]; then
echo "No packege Setting up some stuff."
sudo apt-get --force-yes --yes install beep
fi
sudo modprobe pcspkr
while :
do
if read -t0.01 -s -n1 input; then
echo -n " "
beep -f 200
echo -n "D"
beep -f 300
echo -n "O"
beep -f 400
echo -n "N"
beep -f 500
echo -n "T"
beep -f 600
echo -n " "
beep -f 700
echo -n "T"
beep -f 800
echo -n "O"
beep -f 900
echo -n "U"
beep -f 1000
echo -n "C"
beep -f 900
echo -n "H"
beep -f 800
echo -n " "
beep -f 700
echo -n "T"
beep -f 600
echo -n "H"
beep -f 500
echo -n "E"
beep -f 400
echo -n " "
beep -f 200
echo -n "K"
beep -f 300
echo -n "E"
beep -f 400
echo -n "Y"
beep -f 500
echo -n "B"
beep -f 600
echo -n "O"
beep -f 700
echo -n "A"
beep -f 800
echo -n "R"
beep -f 900
echo -n "D"
beep -f 1000
echo -n " "
beep -r 3 -f 200
else
echo -n "$RANDOM"
beep -l 15 -f 261.63
fi
done
and i love the result thanks to everyone who helped me on this thread and i hope to hear from you soon
thanks again!

[bardo2]

cute drum solo there ;-)

...but...

a whole lot of things, that could be improved upon, but hey: that is how learning goes...

Just a few hints from me:

use comments (you yourself might find them useful - or funny - later)
it is considered bad style to incorporate a one-time installation into a (hopefully) many times to be called script - those are mostly kept separate - or to change a user systems config without his consent
you could also straighten things somewhat (when you find many repetitions in a program, those give a clue for a higher abstraction level to be likely available)
i am sure, you could even change the frequencies used by beep to make them play a bunch of real notes/a tune
--force-yes is WAY too much (read the documentation/man apt-get) you would STOP a surgery, if you were asked: "you are about to cut into vital functions, do you want to continue anyway?"


Still, hey! you are on your way discovering some of the things you can do with an Ubuntu system :-) =d>

[ethan26]

Thank you for the input! the code i used for the installation was from the internet and all i did with that is change the packege name to beep so it would work for my perposes but i am going to make a song play and post it back here again!
if you have any song sugestions let me know.
thank you so much youve really been a big help!

[fugu2]

you might also want to check out
http://stackoverflow.com/questions/5297638/bash-how-to-end-infinite-loop-with-any-key-pressedmight help you along your way
However, I would add this to the top of that script
trap "if [ -t 0 ]; then stty sane; fi" EXIT so that if your script exits early, it will automatically make you stty sane again

[ethan26]

Thank you but what do you mean by:

so that if your script exits early, it will automatically make you stty sane again
thak you again

[fugu2]

so the command
stty -echo -icanon -icrnl time 0 min 0 basically stops normal operation of pressing a key and printing a character. instead it can listen for keys to be pressed and make a decision based on if it detects a key pressed. if you didn't set it back to sane when your program ends, then you might notice non-normal behavior in the console (like no characters showing up when you type). when the script exits, you want to undo this non-blocking effect in the console. the "trap" command is useful for running something later when some condition is met, in our case when the program EXIT. when the program exits it will reset the blocking behavior of the console. You may have noticed the Crtl-C command already which will stop your script before it finishes. If you were to Crtl-C on the middle of the demo script on stackoverflow, it would never execute the stty sane part of the script. the trap would make sure even if you exit early, it will still run stty sane.