How to read one file and replace contents in another file

[Srinivas Palam]

Hi,

I have two files in unix. First file has only loan number and second file has lender number and loan number. I wanted to compare both loan numbers and update lender number with 909090. How do I do that.

Sample First File: First.txt
Loan Number
123456
333333
555555
888888
999999

Sample Second File: Second.txt
Lender Number,Loan Number
345900,123456
567209,888888
780909,345465

After executing the script output in Second.txt should be

Lender Number,Loan Number
909090,123456
909090,888888
780909,345465 ---> No change her, because loan number does not match from both the files.

Your help is grealy appreciated.

[Pat Farrell]

The general approach is to write to a temporary file, and when you are done, delete the original file and rename the temporary file to the original file's name.

[Sujoy Choudhury]

Try this:
Make sure your target file doesn't have space at the end of the line.

#!/usr/bin/ksh

CONST="909090"
LOAN_FILE=one.txt
TARGET_FILE=two.txt
cp $TARGET_FILE $TARGET_FILE.bk

while read line
    do
       if [[ (-z $line) || (`echo $line | grep "^[A-Z]" | wc -l` -eq 1 ) ]]; then
            echo "Skipping line:"$line
            continue;
       fi

       echo "Processing Line:${line}"
       LEN_NUM=`grep ",\$line$" $TARGET_FILE | awk -F"," '{print $1}'`
       echo "Lending Number:"$LEN_NUM
        sed -i "s/^$LEN_NUM\,$line$/$CONST,$line/" $TARGET_FILE  
  done < $LOAN_FILE

[Sujoy Choudhury]

Did this help you?? Are you following your post??