These three file descriptors (you can think of them as “data pipes”) are often called STDIN, STDOUT, and STDERR. By default, if you don’t name or number one explicitly, you’re talking about STDOUT. Standard in, out, and error There are three standard sources of input and output for a program. 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? Source
Does the Iron Man movie ever establish a convincing motive for the main villain? Cannot patch Sitecore initialize pipeline (Sitecore 8.1 Update 3) Does the way this experimental kill vehicle moves and thrusts suggest it contains inertia wheels? Warning: the order of redirection matters: >/dev/null 2>&1 is not the same as 2>&1 >/dev/null Try these two commands with a non-privileged user: ls >/dev/null 2>&1 ls 2>&1 >/dev/null Indeed, in 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 http://askubuntu.com/questions/350208/what-does-2-dev-null-mean
Conventionally, file descriptor '1' is standard output (a.k.a. Does WiFi traffic from one client to another travel via the access point? Both outputs are now on the same chanel (1). >/dev/null: means that the standard output (and the standard error output) is sent to /dev/null. /dev/null is a special file: Data written 1 Dev Null Draw an hourglass Does the Iron Man movie ever establish a convincing motive for the main villain?
no, do not subscribe yes, replies to my comment yes, all comments/replies instantly hourly digest daily digest weekly digest Or, you can subscribe without commenting. Redirect Stderr To Dev Null And Stdout To File Some of the forms of redirection for the Bourne shell family are: Character Action > Redirect standard output 2> Redirect standard error 2>&1 Redirect standard error to standard output < Redirect Could IOT Botnets be Stopped by Static IP addressing the Devices? This answer seems to belong to another question. –sivann Sep 26 at 15:27 add a comment| Your Answer draft saved draft discarded Sign up or log in Sign up using
C Shell Family Some of the forms of redirection for the C shell family are: Character Action > Redirect standard output >& Redirect standard output and standard error < Redirect standard Find 2 Dev Null So why does that also go to /dev/null? 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 I've not dealt much with other shells outside of csh and tcsh.
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 http://askubuntu.com/questions/350208/what-does-2-dev-null-mean This site is not affiliated with Linus Torvalds or The Open Group in any way. Redirect Stdout And Stderr To Dev Null What does the "stain on the moon" in the Song of Durin refer to? Redirect Stderr To Dev Null C These 2 are equivalents: > file and >file.
By default, standard input is connected to the terminal keyboard and standard output and error to the terminal screen. http://supercgis.com/dev-null/redirect-std-error-to-dev-null.html But so there's no performance difference or some such with 2>&- vs 2>/dev/null (other than that some "poorly" written programs don't undrestand 2>&- correctly)? –Det Apr 6 '13 at 14:38 1 Other file descriptor numbers are assigned sequentially to other open files, or can be explicitly referenced in the shell scripts. Should I define the relations between tables in database or just in code? Redirect Stderr To Null Windows
Why do composite foreign keys need a separate unique constraint? Exactly what i wanted! The length of the null device is always zero. /dev/null 2 &1 In Linux What is way to eat rice with hands in front of westerners such that it doesn't appear to be yucky?
cron will only email you if there is some output from you job. So, you discard the output and cron has nothing to send. It redirects file descriptor 2 (STDERR) and descriptor 1 (STDOUT) to /dev/null. >/dev/null This is just an abbreviation for 1>/dev/null. always forces the file to be overwritten.
It can be used to suppress any output. Another way (more convenient?) to disable mail is to use the '-m off' option, i.e. Nobody I asked could tell me what the funny greater-thans, ampersands and numbers after the commands meant, and search engines never turned up anything but examples of it being used without Using >!
Privacy - Terms of Service - Questions or Comments ≡ Menu Home About Linux Shell Scripting TutoriaL RSS/Feed nixCraft Linux and Unix tutorials for new and seasoned sysadmin. Are illegal immigrants more likely to commit crimes? A file descriptor can be a file name of the address of a stream. '&' is the address operator as in the C language.