Using sed with a substitution variable that may have curly braces - bash

Question

I'm writing a script for looping over a set of files in a directory searching for a string (stringA) in one file (srcFile), copying the line that follows it (stringToCopy), and pasting it on the line after another search string (stringB) in another file (outputFile). The copy/paste script that I have so far is as follows
stringA="This is string A"
stringB="This is string B"
srcFile=srcFile.txt
outpuFile=outputFile.txt
replacement="/$stringA/{getline; print}"
stringToCopy="$(awk "$replacement" $srcFile)"
sed -i "/$stringB/!b;n;c${stringToCopy}" $outputFile
The script works great, except when stringToCopy ends up containing curly braces. Example is
srcFile.txt:
This is string A
text to copy: {0}
outputFile.txt:
This is string B
line to be replaced
Once the script is done, I would expect outputFile.txt to be
This is string B
text to copy: {0}
But sed chokes with
sed: -e expression #1, char 106: unknown command: `m'
I've tried hardcoding the problematic string and trying different variations of escaping the curlies and quoting the string, but haven't found a winning combination and I'm at a loss for how to make it work.
EDIT
I had a derp moment and forgot that my stringA also has curly braces, that happened to cause my awk command to math multiple lines. This caused my stringToCopy to have newlines in it which is my real issue, not the curly braces. So the real question is, how to make awk treat curly braces as literal characters so that
srcFile.txt
This is string A: {0}
text to copy: {0}
This is string A:
Other junk
And stringA="This is string A: {0}"
Doesn't set stringToCopy to
text to copy: {0}
Other junk

Answer 1

A bit of a kludge in that we're going to add some extra coding specifically for braces ...
Current situation:
$ awk '/This is string A: {0}/{getline; print}' srcFile.txt
text to copy: {0} # this is the line we want
Other junk # we do not want this line
We can eliminate the second line by escaping the braces in the search pattern, eg:
$ awk '/This is string A: \{0\}/{getline; print}' srcFile.txt
text to copy: {0}
So, how to escape the braces? We can use some explicit parameter expansions to replace the braces with escaped braces in the $stringA variable, keeping in mind that we also need to escape the braces in the parameter expansion phase, too:
$ stringA="This is string A: {0}"
$ stringA="${stringA//\{/\\{}" # replace '{' with '\{'
$ stringA="${stringA//\}/\\}}" # replace '}' with '\}'
$ echo "${stringA}"
This is string A: \{0\}
We can then proceed with the rest of the code as is:
$ replacement="/$stringA/{getline; print}"
$ echo "${replacement}"
/This is string A: \{0\}/{getline; print}
$ stringToCopy="$(awk "$replacement" $srcFile)"
$ echo "${stringToCopy}"
text to copy: {0}
As for the final sed step I had to remove the ! to get it to work correctly:
$ sed -i "/$stringB/b;n;c${stringToCopy}" $outputFile
$ cat "${outputFile}"
This is string B
text to copy: {0}
NOTES:
if you preface your coding with set -xv you can see how variables are being interpreted at each step; use set +xv to turn off
obviously you'll probably run into issues if you do in fact have more than 1 matching row in $srcFile
if you find other characters that need to be escaped then you'll need to add additional parameter expansions for said characters