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Redirect Standard Output And Standard Error To Null

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This site is not affiliated with Linus Torvalds or The Open Group in any way. Now we already have > /dev/null at the end of the script which means all the standard output (STDOUT) will be written to /dev/null. If so, why is it allowed? Reusable Matrix block types When a girl mentions her girlfriend, does she mean it like lesbian girlfriend? have a peek at this web-site

You can also use >> to append. When you run a script that gives you an output and if we add a > /dev/null 2>&1 at the end of the script, we are asking the script to write Redirection simply means capturing output from a file, command, program, script, or even code block within a script (see Example 3-1 and Example 3-2) and sending it as input By the way, you need to have a > in front of /dev/null 2>&1.

Redirect Error To Dev Null

How to slow down sessions? Another way (more convenient?) to disable mail is to use the '-m off' option, i.e. Disable Email By default cron jobs sends an email to the user account executing the cronjob.

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 you can put them before or after the command. By the way, you need to have a > in front of /dev/null 2>&1. Redirect Only Stdout To Dev Null But some programs can bail out with a failure code if write fails - usually block processors, programs using some careful library for I/O or logging to stdandard output.

asked 3 years ago viewed 126720 times active 1 year ago Blog Stack Overflow Podcast #92 - The Guerilla Guide to Interviewing Linked 3 Get current ssh session's originating IP without Redirect Stdout To Dev Null Browse other questions tagged bash redirect stdout or ask your own question. more hot questions question feed lang-sh about us tour help blog chat data legal privacy policy work here advertising info mobile contact us feedback Technology Life / Arts Culture / Recreation http://unix.stackexchange.com/questions/163352/what-does-dev-null-21-mean-in-this-article-of-crontab-basics Reply Link Frank June 30, 2009, 5:15 pm need a command in my bash script to remove some (not all) of the contents of directory2.

How to explain centuries of cultural/intellectual stagnation? Redirect Output To Null Windows I contribute to various database communities such as Oracle, PostgreSQL, Redis and MongoDB. command1 | command2 | command3 > output-file See Example 16-31 and Example A-14.

Multiple output streams may be redirected to one file. M>N # "M" is a file descriptor, which defaults to 1, if not explicitly set. # "N" is a filename. # File descriptor "M" is redirect to file "N." M>&N #

Redirect Stdout To Dev Null

bash chose &> (now also supported by zsh and some pdksh derivatives) though it clearly breaks POSIX compliance since foo &> file is perfectly valid POSIX syntax which means something completely Then stderr is then being redirected into stdout (2>&1), therefore, both stdout and stderr will go to /dev/null So placing this at the end of a crontab job will suppress all Redirect Error To Dev Null What works: Therefore, to obtain the desired effect, you just need to reverse the redirections. & Dev Null A file descriptor can be a file name of the address of a stream. '&' is the address operator as in the C language.

So share up, coders and newbies. :) BZT Reply Link Saartube January 19, 2011, 10:31 am Thank you :)) Reply Link ciccio October 2, 2011, 9:11 am Hi, how can I Check This Out Why is the bridge on smaller spacecraft at the front but not in bigger vessel? Are there any pan-social laws? script says: ping $1 > $1 Please assist if possible Reply Link SilversleevesX July 20, 2010, 4:16 am How reliable, if that's the word I'm looking for, is ending a particular 1 Dev Null

share|improve this answer answered Oct 21 '14 at 13:13 garethTheRed 16.2k23148 1 What if the command that I run in the crontab file do not output anything? So if it doesn't work remember that this is a likely cause and try /dev/null. Why were Native American code talkers used during WW2? Source So… I tried to redirect the stderror & stdout to /dev/null this way: rm * /directory1/directory2/ > 2&>1 /dev/null kept changing /dev/null form a special file & other users need crw-rw-rw-

Something like: (your_command) 1>/dev/null should leave errors alone, that is, going to stout where you can see them. Redirect Stderr To Dev Null And Stdout To File So when your cronjob executes uptime for instance the output of uptime is sent to the user by email. A mail is delivered only when there is output on stdout or stderr.

However, this is not how shell redirection works.

A little note for seeing this things: with the less command you can view both stdout (which will remain on the buffer) and the stderr that will be printed on the cron share|improve this question edited Oct 21 '14 at 13:31 Stéphane Chazelas 179k28289517 asked Oct 21 '14 at 12:59 Aw Qirui Guo 99861625 marked as duplicate by derobert, Braiam, slm♦ Oct Reply Link Martin June 2, 2014, 4:23 am You could use find instead to filter out the files you don't want to delete, or only delete files matching a patter: Delete What Is /dev/null In Linux For example something like rm -rf /home/somename/a.txt.

Now we already have > /dev/null at the end of the script which means all the standard output (STDOUT) will be written to /dev/null. If those answers do not fully address your question, please ask a new question. Is cardinality a well defined function? have a peek here So what your article suggests here is to produce no output, thus sending no mail.

exec 3<> File # Open "File" and assign fd 3 to it. Disable Email By default cron jobs sends an email to the user account executing the cronjob. Is cardinality a well defined function? Why were Native American code talkers used during WW2?

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 rise to the Using exec20.2. share|improve this answer answered Oct 21 '14 at 13:14 chaos 27.5k65095 add a comment| up vote 2 down vote From the manual cron(8): When executing commands, any output is mailed to Does WiFi traffic from one client to another travel via the access point?

Notation: SPACE(n) vs SPACE(O(n)) How to describe very tasty and probably unhealthy food How does a migratory species advance past the Stone Age? How to explain the use of high-tech bows instead of guns If the square root of two is irrational, why can it be created by dividing two numbers? 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 Whatever that is written to it, get discarded or disappears.

share|improve this answer answered Oct 21 '14 at 14:07 Ambrevar 13413 add a comment| up vote 1 down vote Redirection Bash's reference manual says: The operator [n]>&word is used [...] to