open
open( aString [, aMode [ perm ] ] ) -> anIO or nil
open( aString [, aMode [ perm ] ] ) {| anIO | block }

-> nil


Creates an IO object connected to the given stream, file, or subprocess.

If aString does not start with a pipe character (``|''), treat it as the name of a file to open using the specified mode defaulting to ``r'' (see the table of valid modes on page 326). If a file is being created, its initial permissions may be set using the integer third parameter.

If a block is specified, it will be invoked with the File object as a parameter, and the file will be automatically closed when the block terminates. The call always returns nil in this case.

If aString starts with a pipe character, a subprocess is created, connected to the caller by a pair of pipes. The returned IO object may be used to write to the standard input and read from the standard output of this subprocess. If the command following the ``|'' is a single minus sign, Ruby forks, and this subprocess is connected to the parent. In the subprocess, the open call returns nil. If the command is not ``-'', the subprocess runs the command. If a block is associated with an open("|-") call, that block will be run twice---once in the parent and once in the child. The block parameter will be an IO object in the parent and nil in the child. The parent's IO object will be connected to the child's $stdin and $stdout. The subprocess will be terminated at the end of the block.

open("testfile") do |f|
print f.gets
end

produces:

This is line one

Open a subprocess and read its output:

cmd = open("|date")
print cmd.gets
cmd.close

produces:

Sun Jun 9 00:19:39 CDT 2002

Open a subprocess running the same Ruby program:

f = open("|-", "w+")
if f == nil
puts "in Child"
exit
else
puts "Got: #{f.gets}"
end

produces:

Got: in Child

Open a subprocess using a block to receive the I/O object:

open("|-") do |f|
if f == nil
puts "in Child"
else
puts "Got: #{f.gets}"
end
end

produces:

Got: in Child

__________________
Shaalini.S
Be the Best of Whatever you are...