sed command inside while loop is not working for ubuntu - linux

Question

I have two files; the first includes patterns ( file.txt) that I want to search for in the second file (file.cfg).
Once the patter is found in "file.cfg" I want to remove it + whatever comes after it until next Hello that comes at the beginning of the line.
I have created the below script but its not working :
#! /bin/bash
cat file.txt | while read LINE; do
echo $LINE
sed -i "/^$LINE$/,/^Hello/{//p;d;}" "file.cfg"
sed -i "/^$LINE$/d" "file.cfg"
done
It was working fine yesterday on test files, Today I have modified the file's name, and It stopped working.
I am not sure If I changed something by mistake, but if I will use the below from Ubuntu command line, it works :
sed -i "/^Hello World$/,/^Hello/{//p;d;}" "file.cfg"
Also, I added echo in the loop, and I can see each line in "file.txt"
To provide further information, I will give an example of what I need to achieve with this code :
"file.txt" contains patterns I need to find a match in "file.cfg" once the pattern is found, I need to remove it, and anything comes after it until next Hello.
sed -i "/^$LINE$/,/^Hello/{//p;d;}" "file.cfg" -- > this line should remove anything in between.
sed -i "/^$LINE$/d" "file.cfg" --- > remove the pattern itself.
+++++++++
See the below example :
the File.cfg is divided into sections; each section starts with Hello
File.txt contains random sections name; I need a script to read the section's name from File.txt and see if it's available in file.cfg , then remove the section name and all of its contents
File.txt :
Hello World
Hello Mohammad
Hello Scripting
File.cfg :
Hellow xyz
a
b
c
Hello World
v
b
n
Hello stack
q
w
e
The final results should be :
Hellow xyz
a
b
c
Hello stack
q
w
e
Once the section name is found, I need to remove everything until the next "Hello" that comes at the beginning of a line ( new section ).
None of the lines start with Hello except the sections name.

Answer 1

$ awk 'NR==FNR{names[$0]; next} $1=="Hello"{f=($0 in names)} !f' File.txt File.cfg
Hellow xyz
a
b
c
Hello stack
q
w
e
If you want to do "inplace" editing then just like GNU sed, which you're currently using, has -i, GNU awk has -i inplace but note that you're working with 2 input files so you need to write to both of them:
awk -i inplace 'NR==FNR{names[$0]; print; next} $1=="Hello"{f=($0 in names)} !f' File.txt File.cfg
or only activate inplace editing for the 2nd one, see the gawk man page for how to control that. IMHO just using a temp output file is simpler:
tmp=$(mktemp) &&
awk 'NR==FNR{names[$0]; next} $1=="Hello"{f=($0 in names)} !f' File.txt File.cfg > "$tmp" &&
mv -- "$tmp" File.cfg

Answer 2

I like #tripleee's suggestion to create a sed script from the patterns file. It results in a single pass and sed making sed appeals to my sense of humor :)
The first step is to generate the sed script:
sed 's|.*|/^&$/, /^Hello/ {\n\t/^&$/ d\n\t/^Hello/! d\n}|' file.txt
/^Hello World$/, /^Hello/ {
/^Hello World$/ d
/^Hello/! d
}
/^Hello Mohammad$/, /^Hello/ {
/^Hello Mohammad$/ d
/^Hello/! d
}
/^Hello Scripting$/, /^Hello/ {
/^Hello Scripting$/ d
/^Hello/! d
}
In a nut shell, for each address range we want to delete everything except the ending pattern.
I'll generate the above sed using bash process substitution and treat it like a sed program file (or it could be put in a temp file):
#!/bin/bash
sed -f <(
sed 's|.*|/^&$/, /^Hello/ {\n\t/^&$/ d\n\t/^Hello/! d\n}|' file.txt
) file.cfg
I left out the -i in place edit option for testing.
For non-destructive testing, compare the expected results with the output of the script:
diff expect <(./remove.sh) && echo ok