/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 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 the use of dev Null?
Usage. 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 is dev Null in bash?
/dev/null is the bit-bucket: the place where you dump anything you don’t need. So, the STDOUT is redirected to the bit-bucket(trash) and the STDERR is redirected to where the STDOUT is located: the bit-bucket.
What does 2 dev Null mean?
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.
Can you 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.
How do I send data 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.
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.
What creates Dev Null?
So let’s break it down with step-by-step examples. 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.
Is Dev Null a text file?
It’s a special file that’s present in every single Linux system. However, unlike most other virtual files, instead of reading, it’s used to write. Whatever you write to /dev/null will be discarded, forgotten into the void. It’s known as the null device in a UNIX system.
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.