Remove a specific part of string split by multiple-charater delimiter in bash - regex

Question

I'm trying to process my string and steps as below:
mytext='\\[[123 one (/)\n\\[[456 two (/)\n\\[[789 three (/)'
myvar=456
And I want to remove a part of string (and delimiter) that match myvar after split by delimiter \n, the result should be
\\[[123 one (/)\n\\[[789 three (/)
But I still not find out the solution.
If the delimiter is a single character like :, I can be done with sed command:
mytext2='\\[[123 one (/):\\[[456 two (/):\\[[789 three (/)'
myvar2=456
echo $mytext2 | sed -E "s/[^:]*${myvar}[^:]*(:|$)//g"
Result as expected: \\[[123 one (/):\\[[789 three (/)
How can be done if delimiter is a multiple-character in this case?
Thanks.

Answer 1

Even if you use sed -E, you still lack some support (?<=, ?!, ?=, ? etc). I suggest you use perl (Perl Compatible Regular Expressions).
mytext='\\[[123 one (/)\n\\[[456 two (/)\n\\[[789 three (/)';
myvar=456;
echo $mytext | perl -pe "s/(?<=\\\n).*${myvar}.*?(\\\n|$)//g";
Details:
(?<=\\\n): string starts after \n. \\ escape character \
.*${myvar}.*?(\\\n|$): get string which contains value of variable myvar and ends with \n or end of line.
Result.
\\[[123 one (/)\n\\[[789 three (/)

Answer 2

If you can find another delimiter to be used for example, :, you can first replace it with :,
echo $mytext | tr '\n' ':' | sed -E "s/[^:]*${myvar}[^:]*(:|$)//g"
The full script looks like this
mytext='\\[[123 one (/):\\[[456 two (/):\\[[789 three (/)'
myvar=456
v=$(echo $mytext | tr '\n' ':' | sed -E "s/[^:]*${myvar}[^:]*(:|$)//g")
echo $v
If the multiple character delimiter is something like abcd, you can try to use sed to replace it first instead of using tr.

Answer 3

I sugges awk in this case since you may specify the literal multichar delimiter pattern as the input/output field separator, iterate over the fields and discard all those not matching your value:
mytext='\\[[123 one (/)\n\\[[456 two (/)\n\\[[789 three (/)'
myvar=456
awk -v myvar=$myvar 'BEGIN{FS=OFS="\\\\n"} {s="";
for (i=1; i<=NF; i++) {
if ($i !~ myvar) {s = s (i==1 ? "" : OFS) $i;}
}
} END{print s}' <<< "$mytext"
# => \\[[123 one (/)\\n\\[[789 three (/)
See the online awk demo.
NOTES:
BEGIN{FS=OFS="\\\\n"} - sets the input/output field separator to \n
-v myvar=$myvar passes the myvar to awk
s="" - assigns s to an empty string
for (i=1; i<=NF; i++) {...} - iterates over all fields
if ($i !~ myvar) {...} - if the current field value matches myvar...
s = s (i==1 ? "" : OFS) $i;} - append either the current field value to s (if is the first field) or output separator and the current field value (if it is not the first)
END{print s} - prints s after the field checks.