sed replace pattern with newline character

Question

I'm trying to replace a specific "AllowOverride None" to "AllowOverride All" in the httpd.conf file.

Given the file has multiple line with the same pattern I thought I would do a multiline pattern to replace it... Unless sed has a way to choose when it should replace the pattern.

#
# AllowOverride controls what directives may be placed in .htaccess files.
# It can be "All", "None", or any combination of the keywords:
#   Options FileInfo AuthConfig Limit
#
AllowOverride None

to:

#
# AllowOverride controls what directives may be placed in .htaccess files.
# It can be "All", "None", or any combination of the keywords:
#   Options FileInfo AuthConfig Limit
#
AllowOverride All

I was replacing single lines with:

sudo sed -i 's|DocumentRoot "/var/www/html"|DocumentRoot "/var/www/html/test"|' /etc/httpd/conf/httpd.conf

But I'm not sure how to do it if there's multiple lines

Thanks

Answer 1

sed has many ways to do this. For example, with the change command:

sed --in-place '/^AllowOverride All/c\
AllowOverride None\n' httpd.conf

Or, with a better use of substitute:

sed --in-place '/^AllowOverride/s/All/None/'

The latter can be transliterated as 'On lines which begin with AllowOverride, replace the first instance of All with None'.

Answer 2

Turn out you can specify a line number to replace a string:

sudo sed -i '151s/AllowOverride None/AllowOverride All/' httpd.conf

works perfectly.