From: Robert Klemme <bob.news@...>
Date: 2004-08-19T18:00:54+09:00
Subject: Re: Ruby way to update file lines


"Mark Probert" <probertm@nospam-acm.org> schrieb im Newsbeitrag
news:Xns9549BE97C59B0probertmnospamacmorg@198.161.157.145...
> Hi.
>
> I have a need to update a config file.  It uses '#' as a line comment
> marker.  The config file looks like:
>
>  # file comment
>  #
>  name1:foo1:bar:other
>  name2:foo2:bar:other
>  name3:foo3:bar:other
>  name4:foo4:bar:other
>
> The name:foo combination is unique.
>
> What is the most efficient way to read in the file, update the line, and
> then write it back to the file.  One update would be to place a '#' in col
> 1
>
>  #name3:foo3:bar:other
>
> Any thoughts appreciated.
>
> -mark.

Some code thoughts below

Regards

    robert


# match keys
COMMENT = lambda {|key, val| "# #{key}:#{val}"}
DELETE  = lambda { nil }

tasks = {
  "foo:bar" => COMMENT,
  "foo1:bar1" => DELETE,
}

conf = File.readlines("conf.txt")

# manipulate
conf.map! do |line|
  if /^([^:]+:[^:]+):(.*)$/ =~ line && (fun = tasks[$1])
    fun.call $1, $2
  else
    line
  end
end

# remove deleted lines
conf.compact!

File.open("conf-1.txt", "w") {|io| io.puts conf }

#
# alternative -----------------------------------------
#

# use regexp as line matcher
tasks = {
  /^foo1:bar1:/ => lambda {|line| "# #{line}"},
  /^\s*#\s*foo.bar:/ => lambda {|line| line.sub(/^\s*#\s*/, '' )},
}


conf = File.readlines("conf-1.txt")

# manipulate
conf.map! do |line|
  p,f = tasks.find {|patt, fun| patt =~ line}
  f ? f.call( line ) : line
end

# remove deleted lines
conf.compact!

File.open("conf-2.txt", "w") {|io| io.puts conf }