UNIX for Dummies Questions & Answers

#!/usr/bin/ksh
#------------------------------------------------------------------------------------
# Program: query_by_column_name
# Author: Srinivas Y.
# This program takes filename, the delimiter, the column names to be output and the desired output delimiter
# and prints the output in that format
#------------------------------------------------------------------------------------

if [ $# -lt 4 ]
then
  echo "Invalid number of arguments" 1>&2
  echo "Usage: b_column_name <input delimiter> <output delimiter> <filename> <col1> <col2> ...."  1>&2
  exit 1
fi

INP_DLMTR=$1
OUT_DLMTR=$2
INP_FILE_NM=$3
POSLIST=""
COUNT=""

#echo "Input Delimiter : ${INP_DLMTR}"
#echo "output Delimiter: ${OUT_DLMTR}"
#echo "Input File Name : ${INP_FILE_NM}"

shift 3;

while (($#))
do

  COL_NM=$1
  #echo "Column name : ${COL_NM}"

  head -1 ${INP_FILE_NM} | tr ${INP_DLMTR} '\n' | grep -n "^${COL_NM}$" > /tmp/null
  RC=$?
  if [ $RC -ne 0 ]
  then
     echo "Column ${COL_NM} is not found. Aborting ..." 1>&2
     exit $RC
  fi

  COUNT=`head -1 ${INP_FILE_NM} | tr ${INP_DLMTR} '\n' | grep -n "^${COL_NM}$" | wc -l`
  if [ $COUNT -gt 1 ]
  then
     echo "Multiple columns with name ${COL_NM} found. Aborting ..." 1>&2
     exit 1
  fi

  FLD=`head -1 ${INP_FILE_NM} | tr ${INP_DLMTR} '\n' | grep -n "^${COL_NM}$" | cut -d ':' -f 1`
  if [ ! -n "$POSLIST" ]
  then
    POSLIST='$'"$FLD"
  else
    POSLIST="$POSLIST OFS "'$'"$FLD"
  fi
  
  #echo "POSLIST: $POSLIST"
  
  shift
done

echo "awk -F '${INP_DLMTR}' '{print $POSLIST}' OFS='${OUT_DLMTR}' ${INP_FILE_NM}"| sh
RC=$?

exit $RC