#!/bin/bash
 
# The need is to only replace $pattern inside $whole_text, and return the rest
# of the input untouched. But currently is only returning the matched line.
 
# I'm not sure if it's needed, but as @EdMorton recommends, it may be good idea
# to import the variables in a safer way, as explained here:
#     http://c...content-available-to-author-only...n.com/shell/cus-faq-2.html#Q24
#
# Form "d" seems to be the best for compatibility and features:
#
#     awk 'BEGIN{avar=ARGV[1];ARGV[1]=""}$0 == avar' "$svar" file
 
# The following variables really can contain ANY printable character.
# But in order to simplify, here they don't support single quotes.
pattern='<!-- %cmd: for F in $(find ../[0-9]* -maxdepth 0 -type d | sed "s/^\.\.\///"); do echo "<li><a href=\"$F\">$F</a></li>"; done -->'
container='
    <h2>Title</h2>
    <ul>
        <!-- %cmd: for F in $(find ../[0-9]* -maxdepth 0 -type d | sed "s/^\.\.\///"); do echo "<li><a href=\"$F\">$F</a></li>"; done -->
    </ul>
'
container2="line 1\nline 2\n$pattern\nline3\nline4"
 
echo "-------- A: anuhava proposal d22"
echo "-------- problem: doesn't print non-matched lines"
 
awk -v repl="newtext" 'FNR==NR {
	a = a $0; next
}
n = index($0, a) {
	print substr($0, 1, n-1) repl substr($0, n+length(a))
}' <(printf "%s\n" "$pattern") <(echo "$container")
 
 
 
echo "-------- B: anubhava proposal d29 15:30"
echo "-------- It seems to work, need to check receiving text through variable (see C)"
 
awk -v repl="newtext" 'FNR==NR {
	a = a $0; next
} n = index($0, a) {
	$0 = substr($0, 1, n-1) repl substr($0, n+length(a))
} 1' <(printf "%s\n" "$pattern") <(printf 'line 1\nline 2\nbefore %s after\nline 3\nline 4\n' "$pattern")
 
 
echo "-------- C: modified last proposal to receive container text through variable"
echo "-------- IT WORKS!"
 
awk -v repl="newtext" 'FNR==NR {
	a = a $0; next
} n = index($0, a) {
	$0 = substr($0, 1, n-1) repl substr($0, n+length(a))
} 1' <(printf "%s\n" "$pattern") <(printf '%s' "$container")
 

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