Unix - Replace column value inside while loop

Question

I have comma separated (sometimes tab) text file as below:

parameters.txt:

STD,ORDER,ORDER_START.xml,/DML/SOL,Y
STD,INSTALL_BASE,INSTALL_START.xml,/DML/IB,Y

with below code I try to loop through the file and do something

while read line; do
if [[ $1 =  "$(echo "$line" | cut -f 1)" ]] && [[ "$(echo "$line" | cut -f 5)" = "Y"  ]] ; then
//do something...
if [[ $? -eq 0 ]] ; then
// code to replace the final flag
fi
fi
done < <text_file_path>

I wanted to update the last column of the file to N if the above operation is successful, however below approaches are not working for me:

sed 's/$f5/N/'
'$5=="Y",$5=N;{print}'
$(echo "$line" | awk '$5=N')

Update: Few considerations which need to be considered to give more clarity which i missed at first, apologies!

The parameters file may contain lines with last field flag as "N" as well.
Final flag needs to be update only if "//do something" code has successfully executed.
After looping through all lines i.e, after exiting "while loop" flags for all rows to be set to "Y"

karakfa · Accepted Answer · 2018-09-25 19:06:23Z

3

perhaps invert the operations do processing in awk.

$ awk -v f1="$1" 'BEGIN             {FS=OFS=","}
                  f1==$1 && $5=="Y" { // do something
                                      $5="N"}1'  file

not sure what "do something" operation is, if you need to call another command/script it's possible as well.

answered Sep 25, 2018 at 19:06

karakfa

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1 Comment

Vinod Over a year ago

thanks, I have to change the flag only if "do something" command has successfully executed so the order would be as in code

glenn jackman · Accepted Answer · 2018-09-25 20:18:27Z

1

with bash:

(
IFS=,
while read -ra fields; do
    if [[ ${fields[0]} == "$1" ]] && [[ ${fields[4]} == "Y" ]]; then
        # do something
        fields[4]="N"
    fi
    echo "${fields[*]}"
done < file | sponge file
)

I run that in a subshell so the effects of altering IFS are localized.

This uses sponge to write back to the same file. You need the moreutils package to use it, otherwise use

done < file > tmp && mv tmp file

Perhaps a bit simpler, less bash-specific

while IFS= read -r line; do
    case $line in 
        "$1",*,Y) 
            # do something
            line="${line%Y}N"
            ;; 
    esac
    echo "$line"
done < file

edited Sep 25, 2018 at 20:18

answered Sep 25, 2018 at 20:10

glenn jackman

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2 Comments

Vinod Over a year ago

I tried this but after the execution the lines which already has "N" as the flag are missed out completely in the final file, perhaps i should have mentioned that file may contain lines with "N" as well, if its already "N" it should ignore it. Edited the question

Vinod Over a year ago

I added else condition to your code and result is as expected,thanks.

SLePort · Accepted Answer · 2018-09-25 19:06:50Z

0

To replace ,N at the end of the line($) with ,Y:

sed 's/,N$/,Y/' file

answered Sep 25, 2018 at 19:06

SLePort

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