cat on steroids (or cat on a hot ruby roof)

I got to thinking about SuperIO and how it could be used as a swiss army chainsaw to open files, whereever they might be on the net. From there, my fevered mind got to thinking about cat and how the two could be used together. That said, I present ucat — a universal cat, if you will, which does not need to be herded, but rather will do as you ask. It’s expecting to be able to find SuperIO, so you’ll need to make it available.

Other than SuperIO, everything which ucat uses is part of the standard ruby distribution. I’ll admit that this was a good opportunity for me to learn OptionParser — I’ll touch on some of what I’ve learned below.

SuperIO handles the opening of the files, so I first wanted to find the arguments and behaviours I was going to support.

$ cat --help
Usage: cat [OPTION] [FILE]...
Concatenate FILE(s), or standard input, to standard output.

  -A, --show-all           equivalent to -vET
  -b, --number-nonblank    number nonblank output lines
  -e                       equivalent to -vE
  -E, --show-ends          display $ at end of each line
  -n, --number             number all output lines
  -s, --squeeze-blank      never more than one single blank line
  -t                       equivalent to -vT
  -T, --show-tabs          display TAB characters as ^I
  -u                       (ignored)
  -v, --show-nonprinting   use ^ and M- notation, except for LFD and TAB
      --help     display this help and exit
      --version  output version information and exit

With no FILE, or when FILE is -, read standard input.

Report bugs to .

$ cat --help

Usage: cat [OPTION] [FILE]...

Concatenate FILE(s), or standard input, to standard output.

-A, --show-all equivalent to -vET

-b, --number-nonblank number nonblank output lines

-e equivalent to -vE

-E, --show-ends display $ at end of each line

-n, --number number all output lines

-s, --squeeze-blank never more than one single blank line

-t equivalent to -vT

-T, --show-tabs display TAB characters as ^I

-u (ignored)

-v, --show-nonprinting use ^ and M- notation, except for LFD and TAB

--help display this help and exit

--version output version information and exit

With no FILE, or when FILE is -, read standard input.

Report bugs to .

Ok, I have a list of behaviours. Now let’s get parsing the options:

options = {}
OptionParser.new do |opts|
  opts.banner = "Usage: ucat.rb [options]"
  opts.on("-A", "--show-all", "equivalent to -vET") do |opt|
    options[:ends] = true
    options[:non_printing] = true
    options[:tabs] = true
  end
  opts.on("-b", "--number-non-blank", "number nonblank output lines") do |opt|
    options[:non_blank] = true
  end
  opts.on("-e", "equivalent to -vE") do |opt|
    options[:ends] = true
    options[:non_printing] = true
  end
  opts.on("-E", "--show-ends", "display $ at end of line") do |opt|
    options[:ends] = true
  end
  opts.on("-n", "--number", "number all output lines") do |opt|
    options[:number] = true
  end
  opts.on("-s", "--squeeze-blank", "never more than one single blank line") do |opt|
    options[:squeeze_blank] = true
  end
  opts.on("-t", "equivalent to -vT") do |opt|
    options[:non_printing] = true
    options[:tabs] = true
  end
  opts.on("-T", "--show-tabs", "display TAB characters as ^I") do |opt|
    options[:tabs] = true
  end
  opts.on("-u", "(ignored)") do |opt|
  end
  opts.on("-v", "--show-nonprinting", "use ^ and M- notation, except for LFD and TAB") do |opt|
    options[:non_printing] = true
  end
  opts.on_tail("--version", "output version information and exit") do |opt|
    puts Ucat.version.join(".")
    exit
  end
  opts.on_tail("--license", "output license information and exit") do |opt|
    puts "Unless where otherwise noted, Copyright 2008, by Matthew K Williams."
    puts "Released under an MIT License."
    exit
  end
end.parse!

options = {}

OptionParser.new do |opts|

opts.banner = "Usage: ucat.rb [options]"

opts.on("-A", "--show-all", "equivalent to -vET") do |opt|

options[:ends] = true

options[:non_printing] = true

options[:tabs] = true

end

opts.on("-b", "--number-non-blank", "number nonblank output lines") do |opt|

options[:non_blank] = true

end

opts.on("-e", "equivalent to -vE") do |opt|

options[:ends] = true

options[:non_printing] = true

end

opts.on("-E", "--show-ends", "display $ at end of line") do |opt|

options[:ends] = true

end

opts.on("-n", "--number", "number all output lines") do |opt|

options[:number] = true

end

opts.on("-s", "--squeeze-blank", "never more than one single blank line") do |opt|

options[:squeeze_blank] = true

end

opts.on("-t", "equivalent to -vT") do |opt|

options[:non_printing] = true

options[:tabs] = true

end

opts.on("-T", "--show-tabs", "display TAB characters as ^I") do |opt|

options[:tabs] = true

end

opts.on("-u", "(ignored)") do |opt|

end

opts.on("-v", "--show-nonprinting", "use ^ and M- notation, except for LFD and TAB") do |opt|

options[:non_printing] = true

end

opts.on_tail("--version", "output version information and exit") do |opt|

puts Ucat.version.join(".")

exit

end

opts.on_tail("--license", "output license information and exit") do |opt|

puts "Released under an MIT License."

exit

end

end.parse!

One of the things which I learned is that anything which is to be considered an argument can be put in the opts.on method call preceeded by a ‘-‘ — ‘-a’ or ‘–absolutely-nothing’ are both examples. The usage explanation follows the arguments. Unlike the example which OptionParser provides, you don’t need to give both a “-” and “–” type of option for each one.

Ok, let’s start the class.

class Ucat
  @@line_number = 0
  def self.version
    [0,0,1]
  end
  def initialize(arg, options)
    @options = {
      :ends => false,
      :non_printing => false,
      :tabs => false,
      :non_blank => false,
      :number => false,
      :squeeze_blank => false
    }.merge(options)
    arg = STDIN if arg == "-"
    cat(arg)
  end

  def cat(arg)
    prev_line = nil
    f = SuperIO(arg)
    begin
      while (line = f.readline.chop)
        if @options[:squeeze_blank]
         next if (line == "") && (prev_line == "")
        end
        prev_line = line

        # handle the newline
        line = "#{line}$" if @options[:ends]

        # handle tabs
        line.gsub!(/\t/, "^I") if @options[:tabs]

        # handle show non-printing characters
        line = non_printing(line) if @options[:non_printing]

        # line numbering
        line = numbering(line) if (@options[:number] || @options[:non_blank])
        puts line
      end
    rescue EOFError
      f.close
    end
  end
end

class Ucat

@@line_number = 0

def self.version

[0,0,1]

end

def initialize(arg, options)

@options = {

:ends => false,

:non_printing => false,

:tabs => false,

:non_blank => false,

:number => false,

:squeeze_blank => false

}.merge(options)

arg = STDIN if arg == "-"

cat(arg)

end

def cat(arg)

prev_line = nil

f = SuperIO(arg)

begin

while (line = f.readline.chop)

if @options[:squeeze_blank]

next if (line == "") && (prev_line == "")

end

prev_line = line

# handle the newline

line = "#{line}$" if @options[:ends]

# handle tabs

line.gsub!(/\t/, "^I") if @options[:tabs]

# handle show non-printing characters

line = non_printing(line) if @options[:non_printing]

# line numbering

line = numbering(line) if (@options[:number] || @options[:non_blank])

puts line

end

rescue EOFError

f.close

end

Yes, I know, not all the code is there; we’ll add the missing methods in a moment.

We’re keeping line_number as a class variable because we want to be able to keep our count through more than one file without resetting it.

The initializer just sets things up for processing. One thing that is kind of interesting — we have options which have been set up based on the command line options, and we merge them with the defaults so that we always have a “safe” value. Also, we’re using ‘-‘ as the unix standard for STDIN, so if Ucat is passed that string, it does the modification to handle it properly.

cat is where the majority of the work occurs. It opens, via SuperIO a file, then reads it line by line. For each line it does the following:

Remove the newline character
Checks to see if we need to squeeze the blanks.
Handles newline if required.
Handles tabs if required
Handles the non-printing characters if required
Handles line numbering
Finally outputs the result

Of interest is the non_printing method:

  def non_printing(line)
    proc = ""
    line.each_byte do |c|
      proc += case c
              when (0 .. 8): "^#{(c + 64).chr}"
              when (10 .. 11): "^#{(c + 64).chr}"
              when (13 .. 26): "^#{(c + 64).chr}"
              when (27 .. 31): "^#{%w([ \\ ] ^ _)[c - 27]}"
              when 127: "^?"
              when ((c & 128) == 128): "M-0#{c.to_s(8)}"
              else c.chr
              end
    end
    proc
  end

def non_printing(line)

proc = ""

line.each_byte do |c|

proc += case c

when (0 .. 8): "^#{(c + 64).chr}"

when (10 .. 11): "^#{(c + 64).chr}"

when (13 .. 26): "^#{(c + 64).chr}"

when (27 .. 31): "^#{%w([ \\ ] ^ _)[c - 27]}"

when 127: "^?"

when ((c & 128) == 128): "M-0#{c.to_s(8)}"

else c.chr

end

proc

end

It looks at each byte and determines if anything special needs to be done with it. I suggest looking at an ascii character set reference to determine what characters are output. I am ignoring TAB and LFD, per the spec. For anything above 127, I’m outputting “M-” followed by the octal value of the character.

Taking something with a number of control characters, you can see it in action:

$ man man > manpg
$ head manpg | ruby ucat.rb -vn
000001  man(1)                                                                 man(1)
000002
000003
000004
000005  N^HNA^HAM^HME^HE
000006         man - format and display the on-line manual pages
000007
000008  S^HSY^HYN^HNO^HOP^HPS^HSI^HIS^HS
000009         m^Hma^Han^Hn  [-^H-a^Hac^Hcd^Hdf^HfF^HFh^Hhk^HkK^HKt^Htw^HwW^HW]  [-^H--^H-p^Hpa^Hat^Hth^Hh] [-^H-m^Hm _^Hs_^Hy_^Hs_^Ht_^He_^Hm] [-^H-p^Hp _^Hs_^Ht_^Hr_^Hi_^Hn_^Hg] [-^H-C^HC _^Hc_^Ho_^Hn_^Hf_^Hi_^Hg_^H__^Hf_^Hi_^Hl_^He]
000010         [-^H-M^HM _^Hp_^Ha_^Ht_^Hh_^Hl_^Hi_^Hs_^Ht] [-^H-P^HP _^Hp_^Ha_^Hg_^He_^Hr] [-^H-S^HS _^Hs_^He_^Hc_^Ht_^Hi_^Ho_^Hn_^H__^Hl_^Hi_^Hs_^Ht] [_^Hs_^He_^Hc_^Ht_^Hi_^Ho_^Hn] _^Hn_^Ha_^Hm_^He _^H._^H._^H.
$

$ man man > manpg

$ head manpg | ruby ucat.rb -vn

000001 man(1) man(1)

000002

000003

000004

000005 N^HNA^HAM^HME^HE

000006 man - format and display the on-line manual pages

000007

000008 S^HSY^HYN^HNO^HOP^HPS^HSI^HIS^HS

000009 m^Hma^Han^Hn [-^H-a^Hac^Hcd^Hdf^HfF^HFh^Hhk^HkK^HKt^Htw^HwW^HW] [-^H--^H-p^Hpa^Hat^Hth^Hh] [-^H-m^Hm _^Hs_^Hy_^Hs_^Ht_^He_^Hm] [-^H-p^Hp _^Hs_^Ht_^Hr_^Hi_^Hn_^Hg] [-^H-C^HC _^Hc_^Ho_^Hn_^Hf_^Hi_^Hg_^H__^Hf_^Hi_^Hl_^He]

000010 [-^H-M^HM _^Hp_^Ha_^Ht_^Hh_^Hl_^Hi_^Hs_^Ht] [-^H-P^HP _^Hp_^Ha_^Hg_^He_^Hr] [-^H-S^HS _^Hs_^He_^Hc_^Ht_^Hi_^Ho_^Hn_^H__^Hl_^Hi_^Hs_^Ht] [_^Hs_^He_^Hc_^Ht_^Hi_^Ho_^Hn] _^Hn_^Ha_^Hm_^He _^H._^H._^H.

Or, passing in a url:

$ ruby ucat.rb http://www.google.com
Google<!--
body,td,a,p,.h{font-family:arial,sans-serif}.h{font-size:20px}.h{color:#3366cc}.q{color:#00c}.ts td{padding:0}.ts{border-collapse:collapse}#gbar{height:22px;padding-left:2px}.gbh,.gbd{border-top:1px solid #c9d7f1;font-size:1px}.gbh{height:0;position:absolute;top:24px;width:100%}#gbi,#gbs{background:#fff;left:0;position:absolute;top:24px;visibility:hidden;z-index:1000}#gbi{border:1px solid;border-color:#c9d7f1 #36c #36c #a2bae7;z-index:1001}#guser{padding-bottom:7px !important}#gbar,#guser{font-size:13px;padding-top:1px !important}@media all{.gb1,.gb3{height:22px;margin-right:.73em;vertical-align:top}#gbar{float:left}}.gb2{display:block;padding:.2em .5em}a.gb1,a.gb2,a.gb3{color:#00c !important}.gb2,.gb3{text-decoration:none}a.gb2:hover{background:#36c;color:#fff !important}
--><script type="text/javascript"><!--mce:0--></script>
<div id="gbar"><strong class="gb1">Web</strong> <a class="gb1" onclick="gbar.qs(this)" href="http://images.google.com/imghp?hl=en&tab=wi">Images</a> <a class="gb1" onclick="gbar.qs(this)" href="http://maps.google.com/maps?hl=en&tab=wl">Maps</a> <a class="gb1" onclick="gbar.qs(this)" href="http://news.google.com/nwshp?hl=en&tab=wn">News</a> <a class="gb1" onclick="gbar.qs(this)" href="http://www.google.com/prdhp?hl=en&tab=wf">Shopping</a> <a class="gb1" href="http://mail.google.com/mail/?hl=en&tab=wm">Gmail</a> <a class="gb3" onclick="this.blur();gbar.tg(event);return !1" href="http://www.google.com/intl/en/options/"><span style="text-decoration: underline;">more</span> <small>?</small></a>
<div id="gbi"><a></a> <a class="gb2" onclick="gbar.qs(this)" href="http://video.google.com/?hl=en&tab=wv">Video</a> <a class="gb2" onclick="gbar.qs(this)" href="http://groups.google.com/grphp?hl=en&tab=wg">Groups</a> <a class="gb2" onclick="gbar.qs(this)" href="http://books.google.com/bkshp?hl=en&tab=wp">Books</a> <a class="gb2" onclick="gbar.qs(this)" href="http://scholar.google.com/schhp?hl=en&tab=ws">Scholar</a> <a class="gb2" onclick="gbar.qs(this)" href="http://finance.google.com/finance?hl=en&tab=we">Finance</a> <a class="gb2" onclick="gbar.qs(this)" href="http://blogsearch.google.com/?hl=en&tab=wb">Blogs</a>

<a></a> <a class="gb2" onclick="gbar.qs(this)" href="http://www.youtube.com/?hl=en&tab=w1">YouTube</a> <a class="gb2" href="http://www.google.com/calendar/render?hl=en&tab=wc">Calendar</a> <a class="gb2" onclick="gbar.qs(this)" href="http://picasaweb.google.com/home?hl=en&tab=wq">Photos</a> <a class="gb2" href="http://docs.google.com/?hl=en&tab=wo">Documents</a> <a class="gb2" href="http://www.google.com/reader/view/?hl=en&tab=wy">Reader</a> <a class="gb2" href="http://sites.google.com/?hl=en&tab=w3">Sites</a>

<a></a> <a class="gb2" href="http://www.google.com/intl/en/options/">even more »</a></div>
</div>
<div id="guser" style="font-size:84%;padding:0 0 4px"><a href="/url?sa=p&pref=ig&pval=3&q=http://www.google.com/ig%3Fhl%3Den%26source%3Diglk&usg=AFQjCNFA18XPfgb7dKnXfKz7x7g1GDH1tg">iGoogle</a> | <a href="https://www.google.com/accounts/Login?continue=http://www.google.com/&hl=en">Sign in</a></div>
<br id="lgpd" /><a href="/search?q=Large+Hadron+Collider&hl=en"><img title="Large Hadron Collider (LHC)" src="/logos/lhc.gif" border="0" alt="Large Hadron Collider (LHC)" width="330" height="125" /></a>
<form action="/search">
<table border="0" cellspacing="0" cellpadding="0">
<tbody>
<tr valign="top">
<td width="25%"></td>
<td align="center"><input name="hl" type="hidden" value="en" /><input name="ie" type="hidden" value="ISO-8859-1" /><input title="Google Search" maxlength="2048" name="q" size="55" />
<input name="btnG" type="submit" value="Google Search" /><input name="btnI" type="submit" value="I'm Feeling Lucky" /></td>
<td width="25%"><span>  <a href="/advanced_search?hl=en">Advanced Search</a>
  <a href="/preferences?hl=en">Preferences</a>
  <a href="/language_tools?hl=en">Language Tools</a></span></td>
</tr>
</tbody></table>
</form>

<span><a href="/aclk?sa=L&ai=B_Zkz8EPISJ-8F4PwefW44KAH_bH2dJno_6QJwdmc2RPQhgMQARgBIMFUOABQwbGBu_z_____AWDJBg&num=1&sig=AGiWqtwnx0RpL_ua6vjw5jfFxLo04SiemA&q=http://www.google.com/help/ig/art/">Make your homepage beautiful</a> with art by leading designers</span>

<span><a href="/intl/en/ads/">Advertising Programs</a> - <a href="/services/">Business Solutions</a> - <a href="/intl/en/about.html">About Google</a></span>

<span>©2008 - <a href="/intl/en/privacy.html">Privacy</a></span>

<script type="text/javascript"><!--mce:1--></script><script type="text/javascript"><!--mce:2--></script><script type="text/javascript"><!--mce:3--></script>

$ ruby ucat.rb http://www.google.com

Google<!--

body,td,a,p,.h{font-family:arial,sans-serif}.h{font-size:20px}.h{color:#3366cc}.q{color:#00c}.ts td{padding:0}.ts{border-collapse:collapse}#gbar{height:22px;padding-left:2px}.gbh,.gbd{border-top:1px solid #c9d7f1;font-size:1px}.gbh{height:0;position:absolute;top:24px;width:100%}#gbi,#gbs{background:#fff;left:0;position:absolute;top:24px;visibility:hidden;z-index:1000}#gbi{border:1px solid;border-color:#c9d7f1 #36c #36c #a2bae7;z-index:1001}#guser{padding-bottom:7px !important}#gbar,#guser{font-size:13px;padding-top:1px !important}@media all{.gb1,.gb3{height:22px;margin-right:.73em;vertical-align:top}#gbar{float:left}}.gb2{display:block;padding:.2em .5em}a.gb1,a.gb2,a.gb3{color:#00c !important}.gb2,.gb3{text-decoration:none}a.gb2:hover{background:#36c;color:#fff !important}

--><script type="text/javascript"></script>

<div id="gbar"><strong class="gb1">Web</strong> <a class="gb1" onclick="gbar.qs(this)" href="http://images.google.com/imghp?hl=en&tab=wi">Images</a> <a class="gb1" onclick="gbar.qs(this)" href="http://maps.google.com/maps?hl=en&tab=wl">Maps</a> <a class="gb1" onclick="gbar.qs(this)" href="http://news.google.com/nwshp?hl=en&tab=wn">News</a> <a class="gb1" onclick="gbar.qs(this)" href="http://www.google.com/prdhp?hl=en&tab=wf">Shopping</a> <a class="gb1" href="http://mail.google.com/mail/?hl=en&tab=wm">Gmail</a> <a class="gb3" onclick="this.blur();gbar.tg(event);return !1" href="http://www.google.com/intl/en/options/"><span style="text-decoration: underline;">more</span> <small>?</small></a>

<div id="gbi"><a></a> <a class="gb2" onclick="gbar.qs(this)" href="http://video.google.com/?hl=en&tab=wv">Video</a> <a class="gb2" onclick="gbar.qs(this)" href="http://groups.google.com/grphp?hl=en&tab=wg">Groups</a> <a class="gb2" onclick="gbar.qs(this)" href="http://books.google.com/bkshp?hl=en&tab=wp">Books</a> <a class="gb2" onclick="gbar.qs(this)" href="http://scholar.google.com/schhp?hl=en&tab=ws">Scholar</a> <a class="gb2" onclick="gbar.qs(this)" href="http://finance.google.com/finance?hl=en&tab=we">Finance</a> <a class="gb2" onclick="gbar.qs(this)" href="http://blogsearch.google.com/?hl=en&tab=wb">Blogs</a>

<a></a> <a class="gb2" onclick="gbar.qs(this)" href="http://www.youtube.com/?hl=en&tab=w1">YouTube</a> <a class="gb2" href="http://www.google.com/calendar/render?hl=en&tab=wc">Calendar</a> <a class="gb2" onclick="gbar.qs(this)" href="http://picasaweb.google.com/home?hl=en&tab=wq">Photos</a> <a class="gb2" href="http://docs.google.com/?hl=en&tab=wo">Documents</a> <a class="gb2" href="http://www.google.com/reader/view/?hl=en&tab=wy">Reader</a> <a class="gb2" href="http://sites.google.com/?hl=en&tab=w3">Sites</a>

</div>

<div id="guser" style="font-size:84%;padding:0 0 4px"><a href="/url?sa=p&pref=ig&pval=3&q=http://www.google.com/ig%3Fhl%3Den%26source%3Diglk&usg=AFQjCNFA18XPfgb7dKnXfKz7x7g1GDH1tg">iGoogle</a> | <a href="https://www.google.com/accounts/Login?continue=http://www.google.com/&hl=en">Sign in</a></div>

<tbody>

<td width="25%"><span> <a href="/advanced_search?hl=en">Advanced Search</a>

<a href="/preferences?hl=en">Preferences</a>

<a href="/language_tools?hl=en">Language Tools</a></span></td>

</tr>

</tbody></table>

</form>

<span><a href="/aclk?sa=L&ai=B_Zkz8EPISJ-8F4PwefW44KAH_bH2dJno_6QJwdmc2RPQhgMQARgBIMFUOABQwbGBu_z_____AWDJBg&num=1&sig=AGiWqtwnx0RpL_ua6vjw5jfFxLo04SiemA&q=http://www.google.com/help/ig/art/">Make your homepage beautiful</a> with art by leading designers</span>

<span><a href="/intl/en/ads/">Advertising Programs</a> - <a href="/services/">Business Solutions</a> - <a href="/intl/en/about.html">About Google</a></span>

You can download it: ucat.rb

Ramblings » Blog Archive » universal cat redux

September 11, 2008 at 2:39 pm (UTC -5) Link to this comment

[…] Amos King’s blog entry on Inject & Me – BFFs got me to thinking that ucat (see cat on steroids (or cat on a hot ruby roof)) could use inject as opposed to the each_byte. So, instead of def non_printing(line) proc = […]

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