Adding matched string plus additional string after match in same line

Question

I know the title sounds a little confusing, but hopefully my example will clarify my issue.

So I have a file with a list of names (names.txt), for example:

john
david
richard

I'm trying to use a loop to get to the following result:

john john.doe
david david.doe
richard richard.doe

Not sure if using sed is the right command or approach, but here's what I've tried:

for i in $(cat names.txt); do sed "s/$/ $i.doe/" names.txt; done

This 'sort of' works, but spits out an iterative list like this instead:

john john.doe
david john.doe
richard john.doe
john david.doe
david david.doe
richard david.doe
john richard.doe
david richard.doe
richard richard.doe

I've also tried a while IFS= read -r loop as well with similar results. Can't seem to just deal with each line without resulting above.

I'm likely completely off the mark here, but hoping someone can help here.

Apologies in advance. I've used sed before but for rather easier tasks.

General advice: Why is using a shell loop to process text considered bad practice? — G-Man Says 'Reinstate Monica', Apr 20 '22 at 19:19

score 1 · Accepted Answer · answered Apr 20 '22 at 05:39

1

One possible way is to use awk. Command like this can do the work:

awk '{print $1,$1 ".doe"}' names.txt

answered Apr 20 '22 at 05:39

Romeo Ninov

1

Thank you Romeo. I was stuck on using sed that I completely neglected to explore awk. This worked beautifully! – greenteagrasshopper Apr 20 '22 at 05:48
Romeo, if someone puts awk in a for loop, would you rather recommend to use sed instead or explain what is wrong with that approach? – Philippos Apr 20 '22 at 06:30
@Philippos, this depend of particular case. There no only one way to do the things. – Romeo Ninov Apr 20 '22 at 06:33

Philippos · Answer 2 · 2022-04-20T15:08:04.437

1

You midunderstand sed. You don't need to loop over sed, it loops over all lines anyhow. Simply do the replacement

sed 's/.*/& &.doe/' names.txt

.* matches the whole line, and & in the replacement inserts the whole match.

You don't need to switch the tool, just use the tool like it is meant to be.

edited Apr 20 '22 at 15:08

answered Apr 20 '22 at 06:27

Philippos

score 0 · Answer 3 · answered Apr 20 '22 at 05:56

0

Done through sed

sed -r -e  "s/\s+//g" -e "s/.*/& &.doe/g" file1

output

john john.doe
david david.doe
richard richard.doe

answered Apr 20 '22 at 05:56

Praveen Kumar BS

3

Please mention that your code will work with GNU sed only. And while the first part is superfluous for a name file without spaces, an explanation what was wrong with the OP's original attempt would not have been superfluous. – Philippos Apr 20 '22 at 08:06

3 Answers3