Replace a string with sentence containing multiple newline characters [duplicate]

Question

I am trying to replace string with a sentence or paragraph contacting multiple newline characters using shell script. Replacement string will be generated run-time.

eg:

sed /string_to_be_replaced/Replacement(newline character) string (newline character)/g

Any inputs/ideas are welcome. Thanks!

Answer 1

Using GNU sed.

mline="this is\na line\nin multiple\nlines"
sed "s/PATTERN/${mline}/g" <<<"PATTERN here."
this is
a line
in multiple
lines here.

If your input contains / as special character or & which will match as pattern match in sed. Use global Pattern Substitution // to replace/escape all /es and replace back all PATTERNs with \&.

sed "s/PATTERN/${mline//\//\\/}/g; s/PATTERN/\&/" <<<"PATTERN here."

Or either better to use different sed's substation delimiter and escape & again.

sed "s:PATTERN:${mline//&/\\&}:g" <<<"PATTERN here."

And finally if you want it works on actual Enter, first we need to replace all \n with \\n to let them feed to sed as \n. So

Input in multiple lines with actual enter.

mline="th&is is
a line
in mul/tiple
line/s"

The command:

aline="$(sed -z 's:\n:\\n:g;$s:\\n$::' <<<"$mline")
sed "s:PATTERN:${aline//&/\\&}:g" <<<"PATTERN here."

The output is:

th&is is
a line
in mul/tiple
line/s here.