UNIX for Beginners Questions & Answers

#### here filename contain XXXX_YYYY_ZZZZ_DDD.txt as example
while read filename
#splitting a file without extension
full_filename=$filename
noextension=${full_filename%.*}
extension="${full_filename##*.}"

####assigning a patterns to different variable

echo "$noextension"|awk -F'_' '{ print NF-1 }' > countpattern

##### First fi######
if [ "$countpattern" -eq 5 ] ; then
A=$(echo $noextension|cut -d'_' -f1)
B=$(echo $noextension|cut -d'_' -f2)
C=$(echo $noextension|cut -d'_' -f3)
D=$(echo $noextension|cut -d'_' -f4)
E=$(echo $noextension|cut -d'_' -f5)
fi

####Second If########
if [ ! $extension=txt-a $A=HELP] || [ ! $extension=csv -a ! A =HELP ]
then
UPDATE TABLE ########################
rm full_filename
fi

####third if#####
if [ ! $C = "WE" ]
then
UPDATE TABLE ########################
rm full_filename
fi

TMP=csvtxt                                                                     # extension template
while read filename
  do    IFS="._" read -A IARR <<< $filename                                    # split filename into array containing elements and extension (${IARR[-1]})
        if [ ! "${TMP/${IARR[-1]}}" = "$TMP" -a ! "${IARR[0]}" = "HELP" ] ||   # first condition  - former $A is ${IARR[0]} now
           [ ! "${IARR[2]}" = "WE" ]                                           # second condition
          then  # update table                                                 # do whatever necessary
                echo rm $filename                                              # remove echo to remove file
        fi
  done < input

#### here filename contain XXXX_YYYY_ZZZZ_DDD.txt as example
while read filename
do

### split filename on "."
extension="${filename##*.}"
[ "$extension" = "$filename" ] && extension=""
noextension=${filename%.*}
[ "$noextension" = "$filename" ] && noextension=""

### split noextension on "_" to AR[0] AR[1] ... AR[lenAR-1]
## ksh93 takes:
# IFS="_" read -A AR <<< "$noextension"
##
## ksh88 needs:
oIFS=$IFS
IFS="_"
set -f
set -A AR $noextension
IFS=$oIFS
set +f
##
lenAR=${#AR[@]}

### Conditions...
if
  [ "$extension" != "txt" -a "${AR[0]}" = "HELP" ] ||
  [ "$extension" != "csv" -a "${AR[0]}" != HELP ] ||
  [ "$ARR[2]" != "WE" ]
then
# UPDATE TABLE ########################
   echo rm "$filename"
fi

done