Inside a ruby script I want to:
- redirect STDERR to /dev/null
- Issue a system call (e.g. system(tar xf tarfile file) )
- revert to normal STDERR output
I have a script that issues 3-4 system calls that are returning the
following message to STDERR:
warning: Insecure world writable dir /opt, mode 040777
I’d like to suppress these messages (Let’s assume that I can’t change
the permissions on /opt).
An example of one of the lines that is throwing the error is:
x = tar tf mytar.tar # envoke the unix tar command
print x
I can suppress the messages by:
$stderr.reopen(’/dev/null’, ‘w’) # send STDERR to /dev/null
STDERR.puts “can you see me?” # message is suppressed
But I haven’t been able to figure out how to revert STDERR back to
before the the reopen. I only want to suppress this particular
message, but not others that may prove to be useful such as error
messages from the ruby interpreter.
I’ve tried variations of:
stderr = $stderr # save current STDERR IO instance
$stderr.reopen(’/dev/null’, ‘w’) # send STDERR to /dev/null
STDERR.puts “can you see me?” # message is suppressed
$stderr.reopen(stderr) # revert to default behavior (doesn’t
work)
STDERR.puts "what about me? # I want to see this but I don’t
Any suggestions?
On Fri, 25 Aug 2006 12:27:35 -0700, bradjpeek wrote:
$stderr.reopen(‘/dev/null’, ‘w’) # send STDERR to /dev/null
$stderr.reopen(‘/dev/null’, ‘w’) # send STDERR to /dev/null
STDERR.puts “can you see me?” # message is suppressed
$stderr.reopen(stderr) # revert to default behavior (doesn’t
work)
STDERR.puts "what about me? # I want to see this but I don’t
Any suggestions?
Tar is being run in a shell, so you could run:
system(“tar xf mytar.tar 2>/dev/null”)
You could also use the open3 library (from the standard library)
documented on p708 of Pickaxe or at
http://www.ruby-doc.org/stdlib/libdoc/open3/rdoc/index.html
–Ken
On Sat, 26 Aug 2006, bradjpeek wrote:
I’d like to suppress these messages (Let’s assume that I can’t change
the permissions on /opt).
An example of one of the lines that is throwing the error is:
x = tar tf mytar.tar # envoke the unix tar command
print x
the warning is from ruby.
$VERBOSE = nil
will shut it up
if you want it shut up only sometimes do
def quiet
v = $VERBOSE
yield
ensure
$VERBOSE = v
end
then
x = quietly{ tar tf mytar.tar }
print x
Any suggestions?
if you really want fine control over stdin/stdout/stderr of executed
commands
check out my session and open4 libs
http://codeforpeople.com/lib/ruby/session/session-2.4.0/README
http://codeforpeople.com/lib/ruby/open4/open4-0.5.1/README
in particular the Open4::spawn command. both are available as
gem install session
gem install open4
regards.
-a
On 06-08-25, at 15:30, bradjpeek wrote:
$stderr.reopen(’/dev/null’, ‘w’) # send STDERR to /dev/null
$stderr.reopen(’/dev/null’, ‘w’) # send STDERR to /dev/null
STDERR.puts “can you see me?” # message is suppressed
$stderr.reopen(stderr) # revert to default behavior
(doesn’t
work)
STDERR.puts "what about me? # I want to see this but I don’t
Any suggestions?
Modify that slightly:
$stderr_backup = $stderr.dup
$stderr.reopen("/dev/null", “w”)
STDERR.puts “should not see this”
$stderr = $stderr_backup.dup
STDERR = $stderr # can safely ignore the warning
STDERR.puts “foo” # will print foo to the screen
I make no guarantees that this is the best way to do it, infact I can
safely say it’s probably not.
On Sat, 26 Aug 2006, Ken B. wrote:
Tar is being run in a shell, so you could run:
system(“tar xf mytar.tar 2>/dev/null”)
You could also use the open3 library (from the standard library)
documented on p708 of Pickaxe or at
http://www.ruby-doc.org/stdlib/libdoc/open3/rdoc/index.html
it’s ruby that prints the message, not the command
jib:~/shared > ruby -e’ system “true” ’
-e:1: warning: Insecure world writable dir
/dmsp/moby-1-1/ahoward/shared/.,
mode 040777
fyi.
cheers.
-a
You, sir, are a scholar and a gentleman. Worked like a charm.