Shell Programming and Scripting

$> while read I; do if (( $I < 24 )); then echo ok; else echo err; fi; done
22
ok
25
err
28
err

#!/bin/bash

COUNTER=0
MAX=5

while read INPUT; do
   if (( $INPUT > 24 )); then
      if (( $COUNTER < $MAX)); then
         COUNTER=$(($COUNTER + 1))
         echo "Increasing COUNTER to $COUNTER."
      else
         echo "Reached the maximum tries was $COUNTER, aborting."
         break
      fi
   else
      echo "Doing nothing"
   fi
done

exit 0

1
Doing nothing
2
Doing nothing
3
Doing nothing
24
Doing nothing
25
Increasing COUNTER to 1.
26
Increasing COUNTER to 2.
27
Increasing COUNTER to 3.
28
Increasing COUNTER to 4.
10
Doing nothing
30
Increasing COUNTER to 5.
12
Doing nothing
31
Reached the maximum tries was 5, aborting.

#!/bin/ksh
typeset -i i=100          # Set as integer

until [ $i -ge 0 -a $i -le 24 ]
do
  read input?"Please enter a value zero to 24:- "
  i=$input
  if [ "$i" != "$input" ]
  then
     i=100
  fi
done

# Whatever comes next