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Redirect Error To Dev Null In Perl

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Perl Redirect Stdout To Null

Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 6.3 million programmers, just like you, perl stderr helping each other. Join them; it only takes a minute: Sign up Temporarily Redirect STDOUT to /dev/null - Not Working All The Time up vote 3 down vote favorite 1 I am using Server version: Apache/1.3.34 (Debian) mod_perl perl redirect stderr to file - 1.29 By refering to STDIN, STDOUT, and STDERR Streams #!/usr/bin/perl5 package main; use strict 'vars'; { # Our mighty holy legacy code love to print out message in the middle of operation. Shihh.... # Let's quietly redirect those message to /dev/null. my $nullfh = Apache::gensym( ); open $nullfh, '>/dev/null' or warn "Can't open /dev/null: $!"; local *STDOUT = $nullfh; print "BYE BYE WORLD"; # Shouldn't show in webpage. close $nullfh; } print "X BEGIN HELLO

Perl Redirect Stderr To Stdout

WORLD"; # Should show in webpage. I realize that it is not working all the time. For example, I refresh the page for 10 times. x times it will print out "X BEGIN HELLO WORLD". (10-x) time it just print out nothing. I cannot find any reason why it behave this way. May I know anyone of you encounter similar problem as me? perl printing buffer share|improve this question edited Jun 28 '09 at 10:38 J-16 SDiZ 18.2k4171 asked Jun 28 '09 at 9:10 Cheok Yan Cheng 15.9k56261500 add a comment| 4 Answers 4 active oldest votes up vote 4 down vote accepted I need to explicitly store and restore. It works for my case. But I am not sure why. # Take copies of the file descriptors open OLDOUT, '>&STDOUT'; my $returned_values = 0; { # Our mighty holy legacy code love to print out message in the middle of operation. Shihh.... # Let's quietly redirect those message to /dev/null. local *STDOUT; open STDOUT, '>/dev/null' or warn "Can't open /dev/null: $!"; print "BYE BYE WORLD"; # Shouldn't show in webpage. close STDOUT; } # Restore stdout. open STDOUT, '>&OLDOUT' or die "Can't restore stdout: $!"; # Avoid leaks by closing the independent copies. close OLDOUT or die "Can't close OLDOUT: $!"; share|improve this answer edited Jun 30 '09 at 2:34 answered Jun 30 '09 at 1:

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Perl Print To Dev Null

site for Ubuntu users and developers. Join them; it only takes a minute: Sign up Here's how it works: Anybody can ask a question Anybody can answer The best answers are voted up and http://stackoverflow.com/questions/1054579/temporarily-redirect-stdout-to-dev-null-not-working-all-the-time rise to the top What does 2>/dev/null mean…? up vote 54 down vote favorite 34 I want one or two line description about the following command line: grep -i 'abc' content 2>/dev/null command-line grep stdout share|improve this question edited Feb 26 '15 at 9:44 asked Sep 26 '13 at 8:21 Naive 68841322 add a comment| 4 Answers 4 active oldest votes up vote 85 down vote accepted The > http://askubuntu.com/questions/350208/what-does-2-dev-null-mean operator redirects the output usually to a file but it can be to a device. You can also use >> to append. If you don't specify a number then the standard output stream is assumed but you can also redirect errors > file redirects stdout to file 1> file redirects stdout to file 2> file redirects stderr to file &> file redirects stdout and stderr to file /dev/null is the null device it takes any input you want and throws it away. It can be used to suppress any output. share|improve this answer edited Sep 26 '13 at 13:55 answered Sep 26 '13 at 8:38 Warren Hill 10.4k104463 add a comment| up vote 10 down vote In short, it redirects stderr (fd 2) to the black hole (discard output of the command). Some more common use case command > /dev/null 2>&1 & run command in background, discard stdout and stderr command >> /path/to/log 2>&1 & run command and redirect stdout and stderr to log file share|improve this answer edited Dec 29 '14 at 12:51 Griwes 2191213 answered Sep 26 '13 at 8:32 Terry Wang 4,44921521 1 Is there a good reason to use > /dev/null 2>&1 instead of &> /dev/null? –Craig McQueen Nov 30 '15

Q&A Tutorials Poetry RecentThreads NewestNodes Donate What'sNew on Oct 08, 1999 at 00:29UTC ( #730=perlfaq nodetype: print w/replies, xml ) Need Help?? Current Perl documentation can be found at perldoc.perl.org. Here is our local, out-dated (pre-5.6) version: There are three basic ways of http://www.perlmonks.org/?node=How%20can%20I%20capture%20STDERR%20from%20an%20external%20command%3F running external commands: system $cmd; # using system() $output = `$cmd`; # using backticks https://www.novell.com/coolsolutions/feature/19859.html (``) open (PIPE, "cmd |"); # using open() With system(), both STDOUT and STDERR will go the same place as the script's versions of these, unless the command redirects them. Backticks and open() read only the STDOUT of your command. With any of these, you can change file descriptors before the call: open(STDOUT, ">logfile"); system("ls"); or perl redirect you can use Bourne shell file-descriptor redirection: $output = `$cmd 2>some_file`; open (PIPE, "cmd 2>some_file |"); You can also use file-descriptor redirection to make STDERR a duplicate of STDOUT: $output = `$cmd 2>&1`; open (PIPE, "cmd 2>&1 |"); Note that you cannot simply open STDERR to be a dup of STDOUT in your Perl program and avoid calling the shell to do the redirection. This doesn't work: open(STDERR, ">&STDOUT"); perl redirect stderr $alloutput = `cmd args`; # stderr still escapes This fails because the open() makes STDERR go to where STDOUT was going at the time of the open(). The backticks then make STDOUT go to a string, but don't change STDERR (which still goes to the old STDOUT). Note that you must use Bourne shell (sh(1)) redirection syntax in backticks, not csh(1)! Details on why Perl's system() and backtick and pipe opens all use the Bourne shell are in http://www.perl.com/CPAN/doc/FMTEYEWTK/versus/csh.whynot . To capture a command's STDERR and STDOUT together: $output = `cmd 2>&1`; # either with backticks $pid = open(PH, "cmd 2>&1 |"); # or with an open pipe while () { } # plus a read To capture a command's STDOUT but discard its STDERR: $output = `cmd 2>/dev/null`; # either with backticks $pid = open(PH, "cmd 2>/dev/null |"); # or with an open pipe while () { } # plus a read To capture a command's STDERR but discard its STDOUT: $output = `cmd 2>&1 1>/dev/null`; # either with backticks $pid = open(PH, "cmd 2>&1 1>/dev/null |"); # or with an open pipe while () { } # plus a read To exchange a command's STDOUT and STDERR in order to capture the STDERR but le

Asset Management ZENworks Configuration Management ZENworks Endpoint Security Management ZENworks Full Disk Encryption ZENworks Patch Management ZENworks Virtual Appliance Learn more about ZENworks File & Networking Services + File Management Suite Business Continuity Clustering Dynamic File Services File Reporter Filr Micro Focus iPrint Open Enterprise Server Storage Manager Looking for Linux? See our new home at SUSE.com Services & Support + Services Overview Help Yourself Knowledgebase Support Forums Documentation Product Support Lifecycle Let Us Help Open Service Request Entitlement & Access Premium Support Technical Support Handbook Download Patches Drivers Contribute Participate in Beta Report Bug Report Software Vulnerability Share a Tip, Trick, etc. Cool Solutions Consulting Customer Center My Profile My Products My Support My Training Partners Communities + Communities Blog—Expert Views Blog—Technical Free Tools Support Forums About Us + About Us Contact Us Our Customers Executive Management Job Search Events Media Gallery Industry Analysts Press Releases Subscribe How to Buy + How to Buy Overview Request a Call Find a Partner Shop for Training Volume Licensing & Buying Programs > cool solutions home /dev/null Novell Cool Solutions: FeatureBy Manoj Gupta Digg This - Slashdot This Posted: 30 Oct 2007 Technically /dev/null is defined as a null device. Anything written to it is lost forever. If you read the wiki description of /dev/null, you will get to know lots of jargons/metaphors written/referred by UNIX techies a lot. In this article, we will concentrate on the importance of /dev/null, why it is there, and how to use it. Importance When things written to it are lost forever, then why do we need it? This is a valid questions, but we need /dev/null/ to lose information. That's correct, to explain let's take an example: Example 1: Suppose, you want to list all files of directory /var/tmp/ having word "foo" in its content. To achieve the task, we will write something as: ]$ grep -l foo /var/tmp/* /var/tmp/storagedata /var/tmp/storagedata.0 grep: /var/tmp/td.log: Permission denied So we got two files having word "foo"; but we also an annoying error message which was part of STDERR. We were not i

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