Bash While Loop Examples

while [ condition ]
do
   command1
   command2
   command3
done

while [ condition ]; do commands; done
while control-command; do COMMANDS; done

#!/bin/bash
x=1
while [ $x -le 5 ]
do
  echo "Welcome $x times"
  x=$(( $x + 1 ))
done

#!/bin/bash
counter=$1
factorial=1
while [ $counter -gt 0 ]
do
   factorial=$(( $factorial * $counter ))
   counter=$(( $counter - 1 ))
done
echo $factorial

#!/bin/bash
FILE=$1
# read $FILE using the file descriptors
exec 3<&0
exec 0<$FILE
while read line
do
	# use $line variable to process line
	echo $line
done
exec 0<&3

......
..
while getopts ae:f:hd:s:qx: option
do
        case "${option}"
        in
                a) ALARM="TRUE";;
                e) ADMIN=${OPTARG};;
                d) DOMAIN=${OPTARG};;
                f) SERVERFILE=$OPTARG;;
                s) WHOIS_SERVER=$OPTARG;;
                q) QUIET="TRUE";;
                x) WARNDAYS=$OPTARG;;
                \?) usage
                    exit 1;;
        esac
done
.......
..

#!/bin/bash
 
# Script name: block_ips.sh
 
# Set the Internal Field Separator to an octothorpe '#'
IFS='#'
 
# Set input file name here
INPUT="bad-guys.ips.txt"
 
# Read file line-by-line to get an IP and comment to block it using the iptables 
while read -r ip comment
do
	/sbin/iptables -A INPUT -s "$ip" -m comment --comment "$comment" -j DROP
 
done < "$INPUT"

#!/bin/bash
while :
do
	echo "infinite loops [ hit CTRL+C to stop]"
done

while [ condition ]
do
   statements1      #Executed as long as condition is true and/or, up to a disaster-condition if any.
   statements2
  if (disaster-condition)
  then
	break       	   #Abandon the while lopp.
  fi
  statements3          #While good and, no disaster-condition.
done

#!/bin/bash
 
while :
do
	read -p "Enter two numnbers ( - 1 to quit ) : " a b
	if [ $a -eq -1 ]
	then
		break
	fi
	ans=$(( a + b ))
	echo $ans
done

while [ condition ]
do
  statements1      #Executed as long as condition is true and/or, up to a disaster-condition if any.
  statements2
  if (condition)
  then
	continue   #Go to next iteration of I in the loop and skip statements3
  fi
  statements3
done