sed multiple replacements with line range - bash

Question

I have a file with below records
user1,fuser1,luser1,user1#test.com,data,user1
user2,fuser2,luser2,user2#test.com,data,user2
user3,fuser3,luser3,user3#test.com,data,user3
I wanted to perform some text replacements from
user1,fuser1,luser1,user1#test.com,data,user1
to
New_user1,New_fuser1,New_luser1,New_user1#test.com,data,New_user1
so I wrote below sed script.
sed -i -e 's/user/New_user/g; s/fuser/New_fuser/g; s/luser/New_luser/g' file
This works perfect. Now I have a requirement that I want to replace in specific line range.
start=2
end=3
sed -i -e ''${start},${end}'s/user/New_user/g; s/fuser/New_fuser/g; s/luser/New_luser/g' file
but this command is replacing pattern in all lines. example output is,
user1,New_fuser1,New_luser1,user1#test.com,data,New_user1
user2,New_fuser2,New_luser2,user2#test.com,data,New_user2
user3,New_fuser3,New_luser3,user3#test.com,data,New_user3
Looks like range is getting applied only to first expression and remaining expressions are getting applied on whole file. How to apply this range to all expressions?

Answer 1

You can use awk variables to use for this functionality, controlling the row and column numbers used for replacing
awk -vFS="," -vOFS="," -v columnStart=2 -v columnEnd=3 -v rowStart=1 -v rowEnd=2 \
'NR>=rowStart&&NR<=rowEnd{for(i=columnStart; i<=columnEnd; i++) \
$i="New_"$i; print }' file
where the awk variables columnStart, columnEnd, rowStart and rowStart determine which columns and rows to replace with , as the de-limiter adopted.
For your input file:-
$ cat input-file
user1,fuser1,luser1,user1#test.com,data,user1
user2,fuser2,luser2,user2#test.com,data,user2
user3,fuser3,luser3,user3#test.com,data,user3
Assuming I want to do replacement in lines 2 and 3 from columns 3-4, I can set-up my awk as
awk -vFS="," -vOFS="," -v columnStart=3 -v columnEnd=4 -v rowStart=2 -v rowEnd=3 \
'NR>=rowStart&&NR<=rowEnd{for(i=columnStart; i<=columnEnd; i++) \
$i="New_"$i; print }' file
user2,fuser2,New_luser2,New_user2#test.com,data,user2
user3,fuser3,New_luser3,New_user3#test.com,data,user3
To apply on the say the last column, set the columnStart and columnEnd to the same value e.g. say on column 6 and on last line only.
awk -vFS="," -vOFS="," -v columnStart=6 -v columnEnd=6 -v rowStart=3 -v rowEnd=3 \
'NR>=rowStart&&NR<=rowEnd{for(i=columnStart; i<=columnEnd; i++) \
$i="New_"$i; print }' file
user3,fuser3,luser3,user3#test.com,data,New_user3

Answer 2

When using GNU Sed (present on Ubuntu, probably Debian, and probably others).
There is a feature which makes this easy:
https://www.gnu.org/software/sed/manual/sed.html#Common-Commands
A group of commands may be enclosed between { and } characters. This
is particularly useful when you want a group of commands to be
triggered by a single address (or address-range) match.
Example: perform substitution then print the second input line:
$ seq 3 | sed -n '2{s/2/X/ ; p}'
X
Given the original question, this should do the trick:
sed -i -e '2,3 {s/user/New_user/g; s/fuser/New_fuser/g; s/luser/New_luser/g}' file

Answer 3

The following works for me:
START=2
NUM=1
sed -i -e "$START,+${NUM} s/user/New_user/g; $START,+${NUM} s/fuser/New_fuser/g; $START,+${NUM} s/luser/New_luser/g" file
As you can see, there are several changes:
The line range has to be present at each expression
The range should be represented (in this case) as the start line number and number of lines (the number of affected lines is NUM+1)
You put extra apostrophe symbols.

Answer 4

Using a single s command:
start=1
end=2
sed -e "$start,$end s/\([fl]*\)user/New_\1user/g" file
[fl]*user will match user with optional f or l first letter
output:
New_user1,New_fuser1,New_luser1,New_user1#test.com,data,New_user1
New_user2,New_fuser2,New_luser2,New_user2#test.com,data,New_user2
user3,fuser3,luser3,user3#test.com,data,user3