New to linux and have a question about a shell script I'm attempting to write

trace_effect · 12-01-2009, 01:39 AM

Hello,

I am taking a beginning linux class as part of my BS and I had been advised to have a go at making a shell script. The example states:
Create a script that prompts a user to guess a number (that the script creator selects beforehand and enters in the script), if the user guesses the number they are notified and if not the program terminates.

So, i messed around a bit with my limited knowledge and a reference book and came up with a non-working script that im not sure how to fix.

Here is the google doc link:

http://docs.google.com/Doc?docid=0AT...cXNid2dk&hl=en

Any helpful advice/fixes would be most appreciated.

Web31337 · 12-01-2009, 01:56 AM

well, main idea is to use /dev/urandom to generate a random number and then prompt for user input, then compare it with value.
i suggest you'd better read shell-scripting how-to's before you start. (in same google search)

Didier Spaier · 12-01-2009, 02:18 AM

@ http://tldp.org you will find all what you need.

Suggested readings:
http://tldp.org/HOWTO/Bash-Prog-Intro-HOWTO.html

and from this page:
- Introduction to Linux - A Hands on Guide from Machtel Garrels
- Bash Guide for Beginners from Machtel Garrels
- Advanced Bash-Scripting Guide from Mendel Cooper

konsolebox · 12-01-2009, 02:19 AM

You might as well play around with the $RANDOM variable in bash.

... and read: http://www.tldp.org/LDP/abs/html/

-- edit --

in bash, to make the generated output limited to a range of numbers 0 to N - 1 , do something like this:

Code:

NUMBERTOGUESS=$(( RANDOM % N ))
# or
(( NUMBERTOGUESS = RANDOM % N ))

most of the time, 'man bash' should suit everything you need

trace_effect · 12-01-2009, 03:32 AM

Thanks, i'll check those out.

Also, what can i use to keep a count of the amount of guesses?

chrism01 · 12-01-2009, 05:37 PM

A variable.... bash (Unix shells in general) are just a procedural prog lang; nothing fancy, but it does have access to any installed program.
Have a read of those guides; should be fairly straightforward.
Come back with your code if you get stuck.

Welcome to LQ

konsolebox · 12-07-2009, 03:00 AM

Quote:

Originally Posted by chrism01

A variable.... bash (Unix shells in general) are just a procedural prog lang; nothing fancy, but it does have access to any installed program.

Not just that. Bash can do more things: http://sf.net/projects/playshell

You can also *hack* its not-so-obvious capabilities to make it more powerful.. less procedural and more modular

.

catkin · 12-07-2009, 03:41 AM

Quote:

Originally Posted by trace_effect

Also, what can i use to keep a count of the amount of guesses?

That's outside the specification's "if the user guesses the number they are notified and if not the program terminates" but could be done by putting the guess read-and-test code in a loop with a counter

Code:

count=0
while true
do
    <read guess>
    <compare guess and terminate with message detailing $count if correct>
    let count=count+1    
done

konsolebox · 12-10-2009, 12:54 AM

following catkin's suggestion, although less simpler, in bash it can be done like:

Code:

# constants
GUESSRANGE=10
MAXGUESSES=3

# variables
GUESSED=false
NUMBERTOGUESS=$(( ( RANDOM % GUESSRANGE ) + 1 ))   # () may be opt.

# enable extended globbing
shopt -s extglob  # supported starting bash 3.0

# ask
echo "Please guess a number. The range is from 1 to ${GUESSRANGE}."

for (( I = 1; I <= MAXGUESSES; )); do
    read -p "Your number ($(( MAXGUESSES - I + 1 )) tries left): " GUESS

    if [[ "$GUESS" != +([[:digit:]]) ]]; then
        echo "Reply was not a number."
    elif [[ GUESS -lt 1 || GUESS -gt GUESSRANGE ]]; then
        echo "Number was not in range."
    elif [[ GUESS -ne NUMBERTOGUESS ]]; then
        echo "Wrong guess. Please try again."
        (( ++I ))        
    else
        echo "Congratulations. You're correct."
        GUESSED=true
        break
    fi
done

if [[ "$GUESSED" = true ]]; then
    <do some things when user has successfully guessed the number.>
else
    echo "Sorry. Maximum number of guess attempts was reached."
    <do some things when user failed to guess the number.>
fi

-- edit --

The result was obviously a bad programming practice. I just tried to use 'for (( ;; ))' but we can find that it's better to use 'while :; do'.

trace_effect · 12-11-2009, 01:23 AM

Very helpful posts i must say. I'm enjoying learning it.