I need to temporarily redirect standard output to nowhere. Not sure how to do.
Suggestions?
Thanks,
-t0
Assuming you run some *IX:
STDOUT.reopen "/dev/null", "w"
will redirect the standard output (including not just Ruby output,
but even the output of subprocesses) to /dev/null.
Reimer Behrends
···
T. Onoma (transami@runbox.com) wrote:
I need to temporarily redirect standard output to nowhere. Not sure
how to do.
But it also loses the original STDOUT, and M Onoma did say that the
redirection was to be temporary. You can accomplish that by saving
the original value and restoring it later, like this:
old_stdout = STDOUT.dup
STDOUT.reopen( PLATFORM =~ /mswin/ ? "NUL" : "/dev/null" )
. . .
STDOUT.reopen(old_stdout)
Or, if you aren’t invoking any processes external to ruby, you can leave
STDOUT alone and just change $stdout:
$stdout = File.open( PLATFORM =~ /mswin/ ? "NUL" : "/dev/null" )
. . .
$stdout = STDOUT
-Mark
···
On Mon, Nov 24, 2003 at 03:49:21PM +0000, Reimer Behrends wrote:
T. Onoma (transami@runbox.com) wrote:
I need to temporarily redirect standard output to nowhere. Not sure
how to do.Assuming you run some *IX:
STDOUT.reopen “/dev/null”, “w”
will redirect the standard output (including not just Ruby output,
but even the output of subprocesses) to /dev/null.
Minor correction: forgot the mode on my open calls.
Add , “w” to both of the below:
STDOUT.reopen( PLATFORM =~ /mswin/ ? “NUL” : “/dev/null” )
STDOUT.reopen( PLATFORM =~ /mswin/ ? “NUL” : “/dev/null”, “w” )
$stdout = File.open( PLATFORM =~ /mswin/ ? “NUL” : “/dev/null” )
$stdout = File.open( PLATFORM =~ /mswin/ ? “NUL” : “/dev/null”, “w” )
-Mark
···
On Mon, Nov 24, 2003 at 04:37:13PM +0000, Mark J. Reed wrote:
“Mark J. Reed” markjreed@mail.com writes:
Or, if you aren’t invoking any processes external to ruby, you can leave
STDOUT alone and just change $stdout:
Okay, this hints at the answer to a question I’ve been wondering about
for a while now: what’s the difference between STDOUT/STDERR/STDIN and
$stdout/$stderr/$stdin?
It seems your message implies that STDOUT/STDERR/STDIN are IO objects
that when changed, the changes are passed on to children, but if you
change $stdout and friends, those changes are not passed on to
children.
If so, this confuses me greatly, since $stdout prints to stdout, and
if open filehandles (including the magic 3) are inherited by children
(as they are on most *nices), then how can I reopen $stdout without
changing stdout? Why is there such a (to me) confusing and needless
distinction?
Of course, if I inferred incorrectly, disregard the previous
paragraph. 
-=Eric
···
–
Come to think of it, there are already a million monkeys on a million
typewriters, and Usenet is NOTHING like Shakespeare.
– Blair Houghton.
[…]
But it also loses the original STDOUT, and M Onoma did say that the
redirection was to be temporary.
Good catch. I missed that one.
You can accomplish that by saving
the original value and restoring it later, like this:old_stdout = STDOUT.dup
STDOUT.reopen( PLATFORM =~ /mswin/ ? “NUL” : “/dev/null” )
. . .
STDOUT.reopen(old_stdout)
You need
old_stdout.close
here. Otherwise you have a file descriptor leak. Similarly:
Or, if you aren’t invoking any processes external to ruby, you can leave
STDOUT alone and just change $stdout:$stdout = File.open( PLATFORM =~ /mswin/ ? “NUL” : “/dev/null” )
. . .
$stdout.close
$stdout = STDOUT
(And, of course, add the “w” flag to the open call, as you had already
mentioned.)
Reimer Behrends
···
Mark J. Reed (markjreed@mail.com) wrote:
Perfecto!
You are an astute reader, Mark.
Thank you,
-T0
···
On Monday 24 November 2003 05:42 pm, Mark J. Reed wrote:
Minor correction: forgot the mode on my open calls.
Add , “w” to both of the below:On Mon, Nov 24, 2003 at 04:37:13PM +0000, Mark J. Reed wrote:
STDOUT.reopen( PLATFORM =~ /mswin/ ? "NUL" : "/dev/null" )STDOUT.reopen( PLATFORM =~ /mswin/ ? “NUL” : “/dev/null”, “w” )
$stdout = File.open( PLATFORM =~ /mswin/ ? "NUL" : "/dev/null" )$stdout = File.open( PLATFORM =~ /mswin/ ? “NUL” : “/dev/null”, “w” )
-Mark
Right back at you for catching the fd leaks in my examples. Whups.
Thanks.
-Mark
···
On Wed, Nov 26, 2003 at 12:32:02AM +0000, Reimer Behrends wrote:
Mark J. Reed (markjreed@mail.com) wrote:
[…]But it also loses the original STDOUT, and M Onoma did say that the
redirection was to be temporary.Good catch. I missed that one.
Thanks!
-t0
···
On Monday 24 November 2003 05:42 pm, Mark J. Reed wrote:
Minor correction: forgot the mode on my open calls.
Add , “w” to both of the below:On Mon, Nov 24, 2003 at 04:37:13PM +0000, Mark J. Reed wrote:
STDOUT.reopen( PLATFORM =~ /mswin/ ? "NUL" : "/dev/null" )STDOUT.reopen( PLATFORM =~ /mswin/ ? “NUL” : “/dev/null”, “w” )
$stdout = File.open( PLATFORM =~ /mswin/ ? "NUL" : "/dev/null" )$stdout = File.open( PLATFORM =~ /mswin/ ? “NUL” : “/dev/null”, “w” )
-Mark