stdout_issue.rb

class FixDHCP
  attr_reader :line,
              :old_server,
              :new_server
  
  def initialize(line, opts)
    @line = line
    @old_server = opts[:old_server]
    @new_server = opts[:new_server]
  end
  
  def negate_line
    line.sub(/^set/,'delete')
  end
  
  def replace_line
    line.sub(/#{old_server}/,new_server)
  end
  
  def process_line
    "#{negate_line}\n#{replace_line}\n"
  end
end

old_srv = '10.10.10.10'
new_srv = '10.0.0.1'

ssh = Net::SSH.start(Creds[:host], Creds[:uid], password: Creds[:pwd])
sw = Net::SSH::Telnet.new( 'Timeout' => 10,
                           'Prompt'  => /([#>]\s|-)\z/n,
                           'Session' => ssh )

sw.cmd('edit')

Hosts.keys.each do |host|  
  File.open(OutDir + "#{host}.conf","w") do |f|
    output = sw.cmd('show | no-more')
    f.print output
    sleep 3 ### stupid attempt to get stdout to flush
  end
  
  output = []
  sw.cmd("show system services dhcp | display set | match #{old_srv}") do |c|
    next unless c.match(/^(set|delete) /)
    output.push(c.chomp)
  end
  File.open(OutDir + "#{host}.dhcp", "w") do |f|
    output.each do |l|
      fd = FixDHCP.new(l, old_server: old_srv, new_server: new_srv)
      f.print fd.process_line
    end
    sleep 3 ### stupid attempt to get stdout to flush
  end
end

### SAMPLE screwed up output from "*.dhcp" file
 display set | match 10.10.
dev@tma-lab-3300-1# ...cp | display set | match 10.10.1                      0.10 
delete system services dhcp pool 10.0.0.0/8 boot-server 10.10.10.10
set system services dhcp pool 10.0.0.0/8 option 150 array ip-address 10.10.10.10

{master:0}[edit]
dev@tma-lab-3300-1# 
 display set | match 10.10.
dev@tma-lab-3300-1# ...cp | display set | match 10.10.1                      0.10 
set system services dhcp pool 10.0.0.0/8 boot-server 10.0.0.1
set system services dhcp pool 10.0.0.0/8 option 150 array ip-address 10.10.10.10

{master:0}[edit]
dev@tma-lab-3300-1#