From: Tanaka Akira <akr@...17n.org>
Date: 2004-12-06T16:08:29+09:00
Subject: Re: Obtaining mode information on a File object

In article <20041204195115.GA83981@lizzy.catnook.com>,
  Jos Backus <jos@catnook.com> writes:

> Another question... How do I access the File open mode ("w" in this case) on a
> File object?  Example:

% ruby -rfcntl -e '
open("/dev/null") {|f| p f.fcntl(Fcntl::F_GETFL) & Fcntl::O_ACCMODE }
open("/dev/null", "w") {|f| p f.fcntl(Fcntl::F_GETFL) & Fcntl::O_ACCMODE }
open("/dev/null", "r+") {|f| p f.fcntl(Fcntl::F_GETFL) & Fcntl::O_ACCMODE }
'
0
1
2

0 means O_RDONLY.  1 means O_WRONLY.  2 means O_RDWR.

I don't know this is portable enough.

Note that this doesn't work for duplex pipe.

% ruby -rfcntl -e '
open("|echo", "r+") {|f| p f.fcntl(Fcntl::F_GETFL) & Fcntl::O_ACCMODE }
'
0
-- 
Tanaka Akira