Basic number checking problem

Hello all

I am having problems using a bash script to read the input from the user and checking that its a valid number. I only want the user to input a maximum of a 3 number string (321 , 521 , 871 etc.). Anything longer or that includes a chararcter or symbol will display an error message.

heres what i have got so far

 
read input
 
        for ((x=1;x<4;x++)){
        v=`echo $input | cut -c $x`
        if [ $v !-eq (0-9) ]
        then
        echo "error"
        else
        continue
        fi
        }

 

works in bash:

for (( i=1 ; i<4 ; i++))
 do  
  read a 
  echo $a | egrep -w "[0-9]{1,3}" || echo "wrong input"
 done

Hi ChrisHoogie,

grep will make it much easier!

read input
if egrep -q '^[0-9]{1,3}$' <<< "$input"; then
    your command here
else
    echo error
fi

---------- Post updated at 11:14 ---------- Previous update was at 11:09 ----------

Hi funksen,
Watch for your command, it will still accept the following inputs:
1 e24
abc 123

yep you are right, I expected an input of one string without space

the loop is not necessary, thought he want to check three inputs

Cheers for that chebarbudo, works a treat

Funksen the for loop was there to break up the input into characters and check them one by one. Sorry for the confusion but thank you anyway

Hey ChrisHoogie,

Depending on the rest of your script, you can put everything in one line :

read input
egrep -q '^[0-9]{1,3}$' <<< "$input" || { echo "$(basename "$0"): Wrong input" >&2; exit 1; }
the
rest
of
your
script

cheers chebarbudo learning new stuff everday, slowly becoming a script junkie

I have been doing some reading on redirection and still can not find any clear meaning of <<< Can you explain what the third < does

Is there any other reason than to be cool for not using `if (x>999)'? =P

(And that's my first post, talking about something i have no clue about... Doh.)

Hi TaylanUB,

What exactly do you want to check with that?
The proper syntax in shell would be:

if ($x>999); then
    something
fi

and it will fail in most cases.
Have you only tried your command?

terminal80:~# x=abc
terminal80:~# if ($x>999); then echo wrong; else echo right; fi
-bash: rty: command not found
right
terminal80:~# x=123
terminal80:~# if ("$x">999); then echo wrong; else echo right; fi
-bash: 123: command not found
right