4 ms·

Neither Python nor Ruby are best suited for one-liners that the author is emphasising. One liners are bash-fu or commandline-fu. Anything above 100 lines (just

• bad_user 15y ago
  Last 10 lines in a file? 'tail -10 filename.txt' A lot uglier, but you can do a one liner ... ruby -e 'lines=[]; while gets(); lines << $_; \ lines = lines[-10,10] unless $. < 10; end; \ puts lines' < filename.txt The problem with using "the right tool for the right job" is that there are many tools and many jobs, and a general purpose language helps you get things done in case you're stuck. In general I use Ruby for doing string manipulation before piping to other commands. Here's an (ugly) one liner that shows the biggest tables in a MySQL database: mysql -u root godzilla -s -e 'show tables' \ | ruby -ne '$_.strip!; puts %Q{SELECT count(*) \ as cnt, "#$_" as tbl FROM #$_; }' \ | mysql -u root godzilla -s \ | sort -nr \ | ruby -ne 'parts = $_.split /\s+/; \ puts "%40s : %s" % parts.reverse' \ | head -10 You can probably come up with something more clever, but I barely gave that one any thought.
  • jbert 15y ago
    > A lot uglier, but you can do a one liner ... Yeah, but that one-liner reads the whole file. 'tail' can be more clever (and is). 'strace' output: open("a", O_RDONLY) = 3 fstat(3, {st_mode=S_IFREG|0644, st_size=545975512, ...}) = 0 lseek(3, 0, SEEK_CUR) = 0 lseek(3, 0, SEEK_END) = 545975512 lseek(3, 545972224, SEEK_SET) = 545972224 read(3, "tu 11.04 \\n \\l\n\nUbuntu 11.04 \\n "..., 3288) = 3288 'tail' is seeking to the end, then reading backwards. The point being, these 'little tools' can contain important optimisations - they aren't necessarily equivalent to a naive reimplementation.
    • lloeki 15y ago
      Reminds me on that article on GNU grep doing some speedy magic: http://lists.freebsd.org/pipermail/freebsd-current/2010-August/019310.html http://lists.freebsd.org/pipermail/freebsd-current/2010-Augu...
• dramaticus3 15y ago
  tac filename.txt | sed 10q | tac
• nabb 15y ago
  tail can be done in ruby can be quite succinctly with the $< (ARGF) variable: ruby -e'$><<$<.map.last(10)' For the rest of the ruby one-liners in the page the author references, most can be done more easily with standard command line tools (although most people aren't well-versed in sed, so 'ruby -pe puts' might be better than 'sed G').
  • viraptor 15y ago
    There's one big problem with code like that. If you're doing devops-y stuff, then you really, really don't want to debug something like that when your pager goes off at 3am. The cleaner the solution the better, because after you wake up `$><<$<` is just a blurred thing with no meaning...
  • davnola 15y ago
    Cool. That hurts my eyes. ruby -e "print ARGF.readlines.last(10)"
    • rytis 15y ago
      on, say, a 5GB log file?.. If I read this correctly (http://www.ruby-doc.org/core/classes/IO.html#M000914 http://www.ruby-doc.org/core/classes/IO.html#M000914) it'll read the whole file into an array, then spit out last 10 entries?
      • davnola 15y ago
        Yes it does - good point, but the sigil-tastic snippet in the parent reads the whole file into an array, too - it's just harder to tell. Plus the parent snippet is not Ruby 1.9 compatible. Anyways, my version was just to illustrate that sysadmin scripting in Ruby does not have illegible.
• prolepunk 15y ago
  Not that you can't do this in python: python -c "print '\n'.join(open('LICENSE.txt','r').read().split('\n')[:-10])" But this is besides the point.
  • jodrellblank 15y ago
    Your split and join seem redundnant, and open defaults to read-only. print open('whatever.file').readlines()[:-10] But still, don't do that on any log too big to read into memory.