Shell Programming and Scripting

#!/bin/sh
# Beep ip address trough internal pc speaker
# Tested on Debian Linux @NSLU2
# Author: Sebastiaan Giebels, 2007

# Retreive dot-separated ipv4 address from the ifconfig information, using grep and cut:
IPADDRESS=`/sbin/ifconfig | grep -A1 "eth0" | grep "inet" | cut -d: -f 2 |cut -d" " -f1`

# Enable next line for debugging:
#echo $IPADDRESS

#Uncomment this for an example with zeroes in the ip address:
#IPADDRESS="10.0.0.1"

# For all characters in dotted ipv4 address:
for ((a=0; a < ${#IPADDRESS} ; a++))
do
  # Get the next character to process:
  NUMBER=${IPADDRESS:$a:1}

  if [ "." == "$NUMBER" ]
  then
    # Different note to signal a '.' in the address:
    `/usr/bin/beep -l 20 -f 25 -d 20`
  else if [[ "$NUMBER" -ge "0" && "$NUMBER" -le "9" ]]
    then
      # Beep 'NUMBER' times, except for 0 (=beep 10 times):
      if [ "$NUMBER" == "0" ]
      then
        NUMBER=10
      fi
      `/usr/bin/beep -l 45 -f 15 -d 150 -r $NUMBER`

    fi
  fi
  sleep 1
done

for x in $(seq 0 ${#IPADDRESS}); do
    echo $x
done

#for ((a=0; a < ${#IPADDRESS} ; a++))
#while is answer for previous need
a=0
cnt=${#IPADDRESS}
while ((a<cnt))
do
        ....
        ((a+=1))
done

#!/usr/bin/env bash

# @(#) s1	Demonstrate bash extended for syntax.

# Uncomment to run script as external user.
# export PATH="/usr/local/bin:/usr/bin:/bin"
# Infrastructure details, environment, commands for forum posts. 
set +o nounset
pe() { for i;do printf "%s" "$i";done; printf "%s\n"; }
LC_ALL=C ; LANG=C ; export LC_ALL LANG
pe ; pe "Environment: LC_ALL = $LC_ALL, LANG = $LANG"
pe "(Versions displayed with local utility \"version\")"
c=$( ps | grep $$ | awk '{print $NF}' )
version >/dev/null 2>&1 && s=$(_eat $0 $1) || s=""
[ "$c" = "$s" ] && p="$s" || p="$c"
version >/dev/null 2>&1 && version "=o" $p
set -o nounset

pe
pe " Results:"
IPADDRESS="10.0.0.1"

# For all characters in dotted ipv4 address:
for ((a=0; a < ${#IPADDRESS} ; a++))
do
  # Get the next character to process:
  NUMBER=${IPADDRESS:$a:1}
  echo $NUMBER
done

exit 0

% ./s1

Environment: LC_ALL = C, LANG = C
(Versions displayed with local utility "version")
OS, ker|rel, machine: Linux, 2.6.26-2-amd64, x86_64
Distribution        : Debian GNU/Linux 5.0 
GNU bash 3.2.39

 Results:
1
0
.
0
.
0
.
1