/dev/null in Linux is a null device file. This will discard anything written to it, and will return EOF on reading. This is a command-line hack that acts as a vacuum, that sucks anything thrown to it.
What is dev null used for?
The null device is typically used for disposing of unwanted output streams of a process, or as a convenient empty file for input streams. This is usually done by redirection. The /dev/null device is a special file, not a directory, so one cannot move a whole file or directory into it with the Unix mv command.
What means dev null?
/dev/null is the null file. Anything written to it is discarded. Together they mean “throw away any error messages“.
What does >/ dev null 2 >& 1 mean?
2>&1 redirects standard error to standard output. &1 indicates file descriptor (standard output), otherwise (if you use just 1 ) you will redirect standard error to a file named 1 . [any command] >>/dev/null 2>&1 redirects all standard error to standard output, and writes all of that to /dev/null .
What is 2 >/ dev null in Linux?
Specifying 2>/dev/null will filter out the errors so that they will not be output to your console. In more detail: 2 represents the error descriptor, which is where errors are written to. By default they are printed out on the console. > redirects output to the specified place, in this case /dev/null.
Is Dev null a file?
To begin, /dev/null is a special file called the null device in Unix systems. Colloquially it is also called the bit-bucket or the blackhole because it immediately discards anything written to it and only returns an end-of-file EOF when read.
Can I read from Dev Null?
You write to /dev/null every time you use it in a command such as touch file 2> /dev/null. You read from /dev/null every time you empty an existing file using a command such as cat /dev/null > bigfile or just > bigfile. Because of the file’s nature, you can’t change it in any way; you can only use it.
Is writing to dev Null faster?
If a script or program produces lots of output, generally, a reduction of the amount of output will make things run faster. The most radical reduction often seen at the command line is a redirection to /dev/null . However, this can be done in various ways with rather varying results.
How do I send stderr to dev Null?
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). So you need to modify >/dev/null as follows to redirect both output and errors to /dev/null.
What happens when you write to Dev Null?
1 Answer. The null device acts like a black hole. Anything written to it is discarded, and if you try to read from it you receive an end-of-file immediately. It is used to discard unwanted output and to provide null input.
What does 2 mean in Linux?
38. File descriptor 2 represents standard error. (other special file descriptors include 0 for standard input and 1 for standard output). 2> /dev/null means to redirect standard error to /dev/null . /dev/null is a special device that discards everything that is written to it.
How do I redirect a cron job?
To do this, modify the crontab entry and add the output and error redirection as shown below. In the above: > /home/john/logs/backup. log indicates that the standard output of the backup.sh script will be redirected to the backup.
How do you null a file in Linux?
5 Ways to Empty or Delete a Large File Content in Linux
- Empty File Content by Redirecting to Null. …
- Empty File Using ‘true’ Command Redirection. …
- Empty File Using cat/cp/dd utilities with /dev/null. …
- Empty File Using echo Command. …
- Empty File Using truncate Command.
How do I use find in Linux?
The find command is used to search and locate the list of files and directories based on conditions you specify for files that match the arguments. find command can be used in a variety of conditions like you can find files by permissions, users, groups, file types, date, size, and other possible criteria.
What is 2 NUL?
Standard output is going to nul and standard error output (file descriptor 2) is being sent to standard output (file descriptor 1) so both error and normal output go to the same place. In Windows, nul is a null device, which means the output is just flushed and you don’t see it.