Shell Programming and Scripting

#! /usr/local/bin/bash

exec 4>/dev/tty

function readnum
{
        local prompt=$1
        local init=$2
        local backspace=$(echo -e \\b\\c)
        local enter=$(echo -e \\r\\c)
        local savesetting=$(stty -g)
        local keystroke data n i rest reading result
        n=0
        while (( ${#init})) ; do
                rest=${init#?}
                data[n]=${init%$rest}
                init=$rest
                ((n=n+1))
        done
        echo -e "${prompt}"\\c >&4
        while  ((i<n)) ; do
                echo -e ${data[i]}\\c >&4
                ((i=i+1))
        done
        stty -echo -icrnl -icanon min 1 time 0
        reading=1
        while ((reading)) ; do
                keystroke=$(dd bs=1 count=1 2>/dev/null)
                case $keystroke in
                $enter)
                        reading=0
                        ;;
                $backspace)
                        if ((n)) ; then
                                echo -e "${backspace} ${backspace}"\\c >&4
                                ((n=n-1))
                        fi
                        ;;
                *)
                        echo -e ${keystroke}\\c >&4
                        data[n]=$keystroke
                        ((n=n+1))
                esac
        done
        stty "$savesetting"
        echo >&4
        result=""
        i=0
        while  ((i<n)) ; do
                result="${result}${data[i]}"
                ((i=i+1))
        done
        echo $result
        return 0
}

final=$(readnum "well? " 0123)
echo the final number is $final
exit 0

#!/usr/bin/env sh

# @(#) s1       Demonstrate setting default value for read variable.

set -o nounset
echo

debug=":"
debug="echo"

## Use local command version for the commands in this demonstration.

echo "(Versions displayed with local utility \"version\")"
version >/dev/null 2>&1 && version bash

echo

default=9900


read -p "Port number (default is $default): " -e t1
if [ -n "$t1" ]
then
  port_number="$t1"
else
  port_number="$default"
fi

echo
echo " Port number is \"$port_number\""

exit 0

% ./s1

(Versions displayed with local utility "version")
GNU bash 2.05b.0

Port number (default is 9900):

 Port number is "9900"
leap user-problem/220 % ./s1

(Versions displayed with local utility "version")
GNU bash 2.05b.0

Port number (default is 9900): 2001

 Port number is "2001"