Beefy Boxes and Bandwidth Generously Provided by pair Networks
Don't ask to ask, just ask
 
PerlMonks  

Comment on

( #3333=superdoc: print w/ replies, xml ) Need Help??
How is this better than unix "cut"? I know it's different: "cut" uses 1-based column numbers instead of 0-based, and column selection requires a "-f" option flag, and when "-f" is not provided, it exits with usage instructions, instead of listing the fields on the first tab-delimited line of input. But to make it better:
  • you might consider allowing options for selecting a delimiter other than tab (like "cut" does) -- e.g. the delimiter could be a regex (which is something "cut" can't do)
  • you might also consider allowing the output field delimiter to be different from the input field delimiter (something else "cut" can't do)

I notice that you can output fields in arbitrary orders, and even output a given column more than once, and these are handy improvements over cut. But why stop there?

Minor nit-picks:

  • don't use "chop" ("chomp" is better, but see below)
  • given that it's only useful with piped input, die with usage instructions when STDIN is a tty (read about the "-t" function in "perldoc -f -X")
  • it might also be nice to die with instructions when @ARGV contains things that aren't digit strings
  • I like POD. Don't you?
  • given a set of digit strings in @ARGV, your process could be expressed in less code:
    while (<STDIN>) { tr/\r\n//d; # even better than chomp! print join( "\t", ( split /\t/ )[@ARGV] ), "\n"; }
  • (added as an update) BTW, this construct: until ($line=~/\t/) { $line=<STDIN>; } will be an infinite loop if the piped input never contains a tab character. I think you'll want this instead:
    while(<STDIN>) { last if /\t/; } die "No tab-delimited fields found\n" unless ( /\t/ );

In reply to Re: xcol by graff
in thread xcol by sflitman

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":



  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.
  • Log In?
    Username:
    Password:

    What's my password?
    Create A New User
    Chatterbox?
    and the web crawler heard nothing...

    How do I use this? | Other CB clients
    Other Users?
    Others chilling in the Monastery: (7)
    As of 2015-07-31 01:02 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?

      The top three priorities of my open tasks are (in descending order of likelihood to be worked on) ...









      Results (274 votes), past polls