Sed Replace A Multi-Line String

Example

mkdir -p ${HOME}/Documents/sed_playground tee -a ${HOME}/Documents/sed_playground/000-default.conf >/dev/null <<EOF # #This is some test comments # Skip this # <Directory "/var/www/cgi-bin"> AllowOverride None Options +ExecCGI AddHandler cgi-script .cgi .pl Require all granted </Directory> EOF
APACHE_CONF_FILE="${HOME}/Documents/sed_playground/000-default.conf" DIRECTORY_FIND_LEAD_EXP='<Directory "\/var\/www\/cgi-bin">'
DIRECTORY_FIND_FULL_EXP=$(cat <<EOF ${DIRECTORY_FIND_LEAD_EXP}\n\ [ ]*AllowOverride None\n\ [ ]*Options +ExecCGI\n\ [ ]*AddHandler cgi-script \.cgi \.pl\n\ [ ]*Require all granted\n\ <\/Directory> EOF )	DIRECTORY_FILL_FULL_EXP=$(cat <<EOF #<Directory "\/var\/www\/cgi-bin">\n\ #AllowOverride None\n\ #Options +ExecCGI\n\ #AddHandler cgi-script \.cgi \.pl\n\ #Require all granted\n\ #<\/Directory> EOF )
Complex: echo "complex" echo "sedding" sed -i "/${DIRECTORY_FIND_LEAD_EXP}/{N;N;N;N;N;s|${DIRECTORY_FIND_FULL_EXP}|${DIRECTORY_FILL_FULL_EXP}|}" ${APACHE_CONF_FILE}
Simple: echo "simple" echo "sedding" sed -z "s|${DIRECTORY_FIND_FULL_EXP}|${DIRECTORY_FILL_FULL_EXP}|" -i ${APACHE_CONF_FILE}
${HOME}/Documents/sed_playground/000-default.conf # #This is some test comments # Skip this # <Directory "/var/www/cgi-bin"> AllowOverride None Options +ExecCGI AddHandler cgi-script .cgi .pl Require all granted </Directory>	${HOME}/Documents/sed_playground/000-default.conf # #This is some test comments # Skip this # #<Directory "/var/www/cgi-bin"> #AllowOverride None #Options +ExecCGI #AddHandler cgi-script .cgi .pl #Require all granted #</Directory>
sed separate | used to instead of / to avoid escaping of / and . EOF block used to avoid escaping of " Lets have a look:
DIRECTORY_FIND_FULL_EXP=$(cat <<EOF <Directory "/var/www/cgi-bin">\n\ [ ]*AllowOverride None\n\ [ ]*Options +ExecCGI\n\ [ ]*AddHandler cgi-script .cgi .pl\n\ [ ]*Require all granted\n\ </Directory> EOF )	DIRECTORY_FILL_FULL_EXP=$(cat <<EOF #<Directory "/var/www/cgi-bin">\n\ #AllowOverride None\n\ #Options +ExecCGI\n\ #AddHandler cgi-script .cgi .pl\n\ #Require all granted\n\ #</Directory> EOF )

Explanation

1. DIRECTORY_FIND_LEAD_EXP='<Directory "\/var\/www\/cgi-bin">' Special characters must be escaped with a backslash \.
2. [ ]* This will match 0 or many whitespaces. Standard RegEx notation
3. sed -i "/${DIRECTORY_FIND_LEAD_EXP}/{ This will search the file, line-by-line, for ${DIRECTORY_FIND_LEAD_EXP} <Directory "/var/www/cgi-bin">. Note that the search pattern must not contain newline. If, and only if, sed finds ${DIRECTORY_FIND_LEAD_EXP} in the file, then it will proceed with executing the sub-code within the curly braces {}. It will start from the pattern matching line of file.
4. N;N;N;N;N; N tells sed to read the next line after the pattern and attach it to current line. It is important to understand that sed is designed to replace only 1 line at a time, so N will basically force sed to read 2 lines and consider them as a single line with a single newline \n between the two. The newline in the second line will be ignored. By chaining 5 Ns, we are instructing sed to read 6 lines of the file starting with the pattern matching line.
5. s|${DIRECTORY_FIND_FULL_EXP}|${DIRECTORY_FILL_FULL_EXP}| Replace ${DIRECTORY_FIND_FULL_EXP} with ${DIRECTORY_FILL_FULL_EXP}. Note the presence of newlines in the variables. Understanding this part will take some trial and error.

References

Replace a Multi-Line String Using sed SSH Connection Hang Forever Regular Expression