Command Line Processing / Pipes


I’m trying to create a script that that is flexible enough to accept
input that is read from a file whose filename is passed as a command
line argument, or from STDIN via a pipe.
(This is on a WinXP platform rather than Unix)

By way of a simple example, I want both of the following to produce the
same results:

1: 	myScript.rb *.txt

2: cat *.txt | myScript.rb

I have had some joy with the first approach…

	while line = ARGF.gets
		#-- Do the interesting stuff here... or just

print the line.
print line

However, I cannot get anything to work for the pipe approach. I thought
that this would handle piped along STDIN

	while gets()
		line = $_
		print line

but it chucks the following error:

	U:\dev\WM&CAPS\capsfiles>cat testfile.caps | caps.rb
	c:/scripts/caps.rb:1:in `gets': Bad file descriptor

from c:/scripts/caps.rb:1

It does work for STDIO that comes in from the console, but not the pipe.
Oddly (for me), this code works when you pass the filename on the
command line.
Apologies for my newbie stupidity. I’ve had a good half hours google for
help on this but haven’t had any luck.

Any help would be appreciated.

Stuart H.

Senior Analyst Developer / IT Technical Services - Baring Asset
Management (London)
Tel Direct: +44 (0)20-7214 1932 Fax Direct: +44 (0)20-7214 1634
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The following works on Win2k with ruby 1.8.2 (2004-12-25) [i386-mswin32]

type save_sql_env.txt | ruby -n -e “print”

I use ‘type’ as ‘cat’ is not a windows command in Win2k

2006/5/18, Stuart H. [email protected]:

    1:      myScript.rb *.txt

However, I cannot get anything to work for the pipe approach. I thought
c:/scripts/caps.rb:1:in `gets’: Bad file descriptor
from c:/scripts/caps.rb:1

Works for me:

17:02:50 [~]: ruby -e ‘while l=gets; p l; end’ x
17:03:07 [~]: cat x | ruby -e ‘while l=gets; p l; end’
17:03:12 [~]: uname -a
CYGWIN_NT-5.2-WOW64 PDBXPWSRK38 1.5.19(0.150/4/2) 2006-01-20 13:28 i686
17:03:16 [~]: ruby -v
ruby 1.8.4 (2005-12-24) [i386-cygwin]

I guess, you use the windows installer. I prefer the cygwin version as
it has better unix like behavior. Maybe that’s an option for you too.

Kind regards