Shell Programming and Scripting

IXTTIV110827 NANTH AM IKSHIT
ABCDEF  0617 IJAY NAND EENIG
ZXYWVU  0912 AP OOK OONG
PQRSTU100923  NASA  DISH TTY
ASDFG   0223  GHU UMA LAM
QWERT   0111  ATHE SH  THEW

IXTTIV110827 NANTH AM IKSHIT
ABCDEF120518    NAND EENIG  
ZXYWVU120912 AP OOK OON 
PQRSTU100923  NASA  DISH TTY
ASDFG 110223  GHU UMA LAM
QWERT 110111  ATHE SH  THEW

echo "Start"
d=$(date +%Y%m%d)
_yymmdd=${d#??}
_mmdd=${d#????}
_mm=$(date +%m)
_yy=`echo ${_yymmdd}|cut -c1-2`
_yy1=`expr ${_yy} - 1`

cut -c7-12 test.dat |
while read _dd ; do
 ln=`echo ${#_dd}`
 if [[ ${ln} -eq 4 ]] ;
 then
   _fmm=`echo ${_dd} | cut -c1-2`

 if [[ ${_mm} -ge ${_fmm} ]] ; then
      sed 's/  ${_dd}/${_yy}${_dd}/g' test.dat >> test_output.dat
     else
    sed "s/  ${_dd}/${_yy1}${_dd}/g" test.dat >> test_output.dat
   fi
  else
    echo false
 fi
done
echo "End"

 
m=$(date +%m);cy=$(date +%y);py=$(echo $(date +%y) - 1 | bc);awk -v m="$m" -v py="$py" -v cy="$cy" '{firstpart=substr($0,1,6);lastpart=substr($0,14,length($0));a=substr($0,7,6);gsub(" ","",a);if(length(a)<6){if(substr(a,1,2)<m){a=py""a;print firstpart""a""lastpart}else{a=cy""a;print firstpart""a""lastpart}}else{print}}' input.txt

[root@host dir]# cat input
IXTTIV110827 NANTH AM IKSHIT
ABCDEF  0617 IJAY NAND EENIG
ZXYWVU  0912 AP OOK OONG
PQRSTU100923 NASA DISH TTY
ASDFG   0223 GHU UMA LAM
QWERT   0111 ATHE SH THEW
[root@host dir]# 
[root@host dir]# cat test.sh
#! /bin/bash
while read x
do
    if [ "${x:6:2}" == "  " ]
    then
        if [ ${x:8:2} -ge $(date +%m) ]
        then
            echo "${x:0:6}$(date +%y)${x:8}"
        else
            echo "${x:0:6}$(date -d "-1 year" +%y)${x:8}"
        fi
    else
        echo $x
    fi
done < input
[root@host dir]#
[root@host dir]# ./test.sh
IXTTIV110827 NANTH AM IKSHIT
ABCDEF120617 IJAY NAND EENIG
ZXYWVU120912 AP OOK OONG
PQRSTU100923 NASA DISH TTY
ASDFG 110223 GHU UMA LAM
QWERT 110111 ATHE SH THEW
[root@host dir]#

#!/bin/ksh93

month=$(printf "%(%m)T" "now")
thisyear=$(printf "%(%y)T" "now")
lastyear=$(printf "%(%y)T" "last year")

while read x
do
    if [[ "${x:6:2}" == "  " ]]
    then
        if [[ ${x:8:2} -ge $month ]]
        then
            echo "${x:0:6}${thisyear}${x:8}"
        else
            echo "${x:0:6}${lastyear}${x:8}"
        fi
    else
        echo $x
    fi
done < infile