Using sed to replace multiline

Question

I'm trying to replace the following section of a YAML file:

  ssl:
    enabled: false

to read

  ssl:
    enabled: true

I've tried this, which failed: sed -i s/ssl:\n enabled: false/ssl:\n enabled: true/g

Answer 1

You can use sed ranges:

sed '/^ *ssl:/,/^ *[^:]*:/s/enabled: false/enabled: true/' file

The range boundaries are /^ *ssl:/ (start of the ssl section) and /^ *[^:]*:/ (any other section).

The s is the usual substitution command.

Answer 2

Use a YAML-aware tool. For example, in Perl, you can

perl -MYAML=LoadFile,DumpFile -we '
    $y = LoadFile("file");
    $y->{ssl}{enabled} = "true" if $y->{ssl}{enabled} eq "false";
    DumpFile("file.new", $y);'

Answer 3

Sorry, but I will agree with @choroba and tell you to use a tool able to parse and write yaml. Sed parsing is not the right way. you might have different indentation, several continuous endlines. The regexp would get overly complicated and you would end up writing your own Yaml parser.

Here is a solution in ruby That you can use in Bash shell

echo "ssl:
enabled: false
" | bundle exec ruby -e "require 'psych';
 c = Psych.load(STDIN.read); c['ssl']['enabled'] = true;
 puts c.to_yaml" > updated_dest.yml

if you want a shell script that takes two params, its also easy

#!/usr/bin/env ruby

require 'psych'
c = Psych.load_file(ARGV.shift)
c['ssl']['enabled'] = true
File.open(ARGV.shift, 'wb+') {|f| f.write(c.to_yaml)}