From: Ernest Ellingson <erne@...>
Date: 2001-03-26T00:56:07+09:00
Subject: [ruby-talk:13198] Re: Reading a file backwards

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At 16:50 3/25/2001 +0900, you wrote:
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On Sun, 25 Mar 2001 14:10, I think Daniel Berger wrote:
 > Hi all,
 >
 > Old Perl programmer, new to Ruby.  Is there a method/module out there for
 > reading a file backwards?  This would be useful for logfiles, for example.
 >
 > Thanks in advance.
 >
 > Dan

Hi Dan,

perhaps something like this is what you want?

synack@eugene:~/tmp/fox-0.99.166/textedit$ cat > testFile
line 1
line 2
line 3
synack@eugene:~/tmp/fox-0.99.166/textedit$ irb
irb(main):001:0> f = File.new("testFile")
#<File:0x402281d4>
irb(main):002:0> f.readlines.reverse.each { |line| p line }
"line 3\n"
"line 2\n"
"line 1\n"
["line 3\n", "line 2\n", "line 1\n"]


Here's a little ruby script I use for watching a log file

if(!ARGV[0] || !ARGV[1])
      puts "usage  ruby tailReverse.rb Filename bytesToRead [interval in secs]"
      exit
end
x=ARGV[0]
y=ARGV[1]
z=ARGV[2]
tint=60
if !z
   tint=60
else
   tint=z.to_i
end
while tint > 0 do
   f=File.new(x)
   s=f.stat
   if s.size <= y.to_i
     f.each {|line| puts "#{line}"}
   else
     f.seek(-y.to_i, IO::SEEK_END)
     f.readlines.reverse.each {|line| puts "#{line}"}
   end
   f.close
   puts "--------------------------------------------------"
   sleep(tint)
end

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