$ more master.sh
#!/bin/ksh
echo "Add new user account to master "
echo -n "masterlogin: " ;read masterlogin
Search_masterlogin=`grep -i $masterlogin passwd.master|awk -F: '{print $1}'`
echo "Value of Search_masterlogin :$Search_masterlogin"
if [ "$Search_masterlogin" = "$masterlogin" ] ;then
echo "master user account found"
exit 0
fi
####### Identify available free UID ###################
Available_UID=`grep -n "7000" passwd.master |awk -F":" '{print $1-3 "," $1+3 "p"}' |xargs -t -i sed -n {} passwd.master`
echo $Available_UID
echo -n "Enter the previous UID: " ; read previousUID
echo -n "Enter the master UID: " ;read masterUID
echo -n "Enter the master GID:" ;read masterGID
echo -n "Enter the user fullname :" ;read username
echo -n "Enter the home directory :" ;read homedirectory
echo -n "Enter the shell :" ;read shell
echo -n "Enter the server name :" ; read servername
finel_update=`$masterlogin:x:$masterUID:$masterGID:$username:$homedirectory:$shell:$servername
cat passwd.master |sed ' /$previousUID/ a\$finel_update '
$

$ more passwd.master
jamishra:x:6846:8579:jamishra:/app/home/jamishra:/bin/bash
ajaygupt:x:6847:8579:ajaygupt:/app/home/ajaygupt:/bin/bash
redwards:x:6848:8134:Edwards, Ronald :/home/users/redwards
krisvasu:x:6849:8360:Vasu, Krishnadas:/home/readgrp/krisvasu:/bin/ksh
malam:x:6850:9014:Alam, Mahfooz:/app/home/malam:/bin/ksh
#---- range 7000 - SysAdmin applications
cricka:x:7001:8011:AT:/atmdev/home/crickatm:/bin/ksh
cricki:x:7002:8012:Int:/infdev/home/crickinf:/bin/ksh
oracle:x:7003:2002:Oracle:/var/home/oracle:/bin/ksh
dba:x:7004:2002:Oracle DBA:/var/home/dba:/bin/ksh:
named:x:7005:7005:Named:/var/named:/bin/false

$

 Script :-

#!/bin/ksh
echo "Add new user account to master "
echo -n "masterlogin: " ;read masterlogin
Search_masterlogin=`grep -i $masterlogin passwd.master|awk -F: '{print $1}'`
echo "Value of Search_masterlogin :$Search_masterlogin"
if [ "$Search_masterlogin" = "$masterlogin" ] ;then
echo "master user account found"
exit 0
fi
####### Identify available free UID ###################
Available_UID=`grep -n "7000" passwd.master |awk -F":" '{print $1-3 "," $1+3 "p"}' |xargs -t -i sed -n {} passwd.master`
echo $Available_UID
echo -n "Enter the previous UID: " ; read previousUID
echo -n "Enter the master UID: " ;read masterUID
echo -n "Enter the master GID:" ;read masterGID
echo -n "Enter the user fullname :" ;read username
echo -n "Enter the home directory :" ;read homedirectory
echo -n "Enter the shell :" ;read shell
echo -n "Enter the server name :" ; read servername
finel_update="$masterlogin:x:$masterUID:$masterGID:$username:$homedirectory:$shell:$servername"
sed ' /'$previousUID'/ a\'$finel_update' ' passwd.master
$


Script output :-

Enter the previous UID: 6850
Enter the master UID: 6851
Enter the master GID:999
Enter the user fullname :susindran
Enter the home directory :/home/ssuruli
Enter the shell :/bin/ksh
Enter the server name :machard
jamishra:x:6846:8579:jamishra:/app/home/jamishra:/bin/bash
ajaygupt:x:6847:8579:ajaygupt:/app/home/ajaygupt:/bin/bash
redwards:x:6848:8134:Edwards, Ronald :/home/users/redwards:/bin/ksh
krisvasu:x:6849:8360:Vasu, Krishnadas:/home/readgrp/krisvasu:/bin/ksh
malam:x:6850:9014:Alam, Mahfooz:/app/home/malam:/bin/ksh
ssuruli:x:6851:999:susindran:/home/ssuruli:/bin/ksh:
#---- range 7000 - SysAdmin applications


But its not reflecting in file :-

$ more passwd.master
jamishra:x:6846:8579:jamishra:/app/home/jamishra:/bin/bash
ajaygupt:x:6847:8579:ajaygupt:/app/home/ajaygupt:/bin/bash
redwards:x:6848:8134:Edwards, Ronald :/home/users/redwards:/bin/ksh
krisvasu:x:6849:8360:Vasu, Krishnadas:/home/readgrp/krisvasu:/bin/ksh:
malam:x:6850:9014:Alam, Mahfooz:/app/home/malam:/bin/ksh