You can send output to /dev/null, by using command >/dev/null syntax. However, this will not work when command will use the standard error (FD # 2).
| Tutorial details | |
|---|---|
| Difficulty | Easy (rss) |
| Root privileges | No |
| Requirements | bash/ksh |
| Time | 1m |
Syntax to redirect error and output messages to /dev/null
The syntax discussed below works with Bourne-like shells, such as sh, ksh, and bash:
$ command > /dev/null 2>&1 $ ./script.sh > /dev/null 2>&1 $ ./example.pl > /dev/null 2>&1
OR
command &>/dev/null job arg1 arg2 &>/dev/null /path/to/script arg1 &>/dev/null
You can also use the same syntax for all your cronjobs to avoid emails and output / error messages:
@hourly /scripts/backup/nas.backup >/dev/null 2>&1
OR
@hourly /scripts/backup/nas.backup &>/dev/null
Redirect both standard error and standard out messages to a log file
You can always redirect both standard error (stdin) and standard out (stdout) text to an output file or a log file by typing the following command:
command > file 2>&1 /path/to/my/cool/appname > myapp.log 2>&1
Want to close stdout and stderr for the command being executed on a Linux/Unix/BSD/OSX bash shell?
Try the following syntax:
## Thanks http://www.cyberciti.biz/faq/how-to-redirect-output-and-errors-to-devnull/#comment-40252 ## command 1>&- 2>&- ## Note: additional '&' at the end of job to put it in backgrounds ## job 1>&- 2>&- & command 1>&- 2>&- &
See man pages: ksh(1)
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Another way to do it:
$ command &>/dev/null
Or you can close stdout and stderr for the command being executed:
$ command 1>&- 2>&-
Remember to add an additional & at the end of the statement to run the command in the background. Thank you Giuseppe for the tip.
What do you mean by “close stdout and stderr” ?
Thanks
Thanks! I was searching how resolve this problem, and your solution work perfect for me!
need a command in my bash script to remove some (not all) of the contents of directory2.
The script does NOT run as root, which works because it removes the correct files but not the root-level stuff in directory2 (that I don’t want to remove).
Problem is users get confused by the “permission denied” msgs output by the “rm”. 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-
Will the recommended approaches allow me to redirect to /dev/null without messing it up for others?
You could use find instead to filter out the files you don’t want to delete, or only delete files matching a patter:
Delete all files except those with “attachments” in the name:
# find . ! -name '*attachments*' -exec rm -v {} \;Delete all files with “attachments” in the name:
# find . -name '*attachments*' -exec rm -v {} \;Find is very versitile, it’s pretty cool what you can acheive with find.
how does one redirect output from text file processing to a script file that uses the command line variable $1.
file iplist has a long list of IP’s on the network and i need to send this to a script that creates a file with the ping info.
script says: ping $1 > $1
Please assist if possible
How reliable, if that’s the word I’m looking for, is ending a particular command in a script with a redirect like “2>/dev/null” ? What have folks’ experiences been with the different commands and bash/sh versions when trying it this way?
I know it’s not recommended, but for someone like myself, with scripts they either run daily or don’t run for months and then go through a spate of executing them two and three times a day (only to go back to seldom running them until the next time it happens), it would be very convenient and not too too anxiety-producing to run a script and know that whatever passable or critical errors it comes up with are being suppressed.
I’m much more inclined to put up with circumstances after the fact, and I seldom write anything that’s too destructive (on the system or OS/hardware install and performance level, at any rate) for a little error like Exiv2 complaining about some JPG file’s Photoshop IFD entry being out of bounds.
So share up, coders and newbies. :)
BZT
Thank you :))
Hi,
how can I redirect output to /dev/null BUT errors on sdout.
I mean: I want to launch a command:
– if all goes good —> no output
– if something goes wrong —> output of errors
Thanks,
Ciccio
ciccio –
I think it would be the opposite of sending errors to the bucket.
Something like:
(your_command) 1>/dev/null
should leave errors alone, that is, going to stout where you can see them. I’m sure you have something in mind where both good and bad output would normally go to stdout.
BZT
ciccio, the order of the redirection counts.
use:
command 2>&1 1>/dev/null
No, it does not matters. So following two are the same command:
AND
Hello,
The order is important :
$ ls non_existing_folder 1>/dev/null 2>&1
(no output)
$ ls non_existing_folder 2>&1 1>/dev/null
ls: non_existing_folder: No such file or directory
echo “open 192.168.1.10 8080″| telnet | grep –color=auto “Connected to”
gives the following output:
——————————————————-
Connection closed by foreign host.
Connected to 192.168.1.10 (192.168.1.10)
——————————————————-
How can I get rid of “Connection closed by foreign host.” ?
@smilyface
you can close (omit) the stderr output from telnet command
echo “open 192.168.1.10 8080″| telnet 2>&- | grep –color=auto “Connected to”
Hi
I tried like below
ping 127.0.0.1 > /dev/null 2>&1
“but i am getting out as ” Ambiguous output redirect”
Please suggest me
Put in bash script:
exec 2>/dev/null
before your commands. And avoid redirection in the command itself.
l often do the following and I do not want an error (just a 0 length file)
You get a valid output if the command works, otherwise the error is sent to /dev/null
file=`ls doesthisfileexist 2>/dev/null`
if [ -n $file ] ; then
do something
fi
Why not:
if [ ! -f $FILE ] then echo "File does not exist" fiI just stumbled upon this article… FYI ‘command > /dev/null 2>&1` won’t work in every scenario. For example, this will still output an error message:
ps -ef | grep | grep ps > /dev/null 2>&1
Try:
That is a pretty slick little trick. Didn’t know that one. Thanks!
How to get the error help in shell window
Thanks!
Exactly what i wanted!
Hi,
Please tell me how to redirect the output from a script to a log file so that i can save all the details which i am capturing in the script using read command.
Here is a snippet of my code:
echo “Enter the number”
read $N > text
….
If i open text in vi i am getting blank lines and i have saved my script as number.sh and done chmod on the script to give it user permissions as well.
Add the following at the top of your script:
Example:
16011772255fc281187f93a_000004
FYI to use standard out AND error out in a bash script, you cannot have a space between > and &. It’ll give you some wacky error. Just like written on his page, be sure to use >& so that they are together. I just figured this out after battling with the error I previously mentioned. Good luck!