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What is Dev Null in UNIX?

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.

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 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.

Why do we use dev Null?

The most common use of /dev/null is to get rid of standard out, standard error, or both. Selecting which data source you want to squelch is easy. Get rid of standard output with commands like echo hello > /dev/null or echo hello 1> /dev/null. Get rid of errors with commands like touch file 2> /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.

What does 2 Dev Null mean in Linux?

The N> syntax in Bash means to redirect a file descriptor to somewhere else. 2 is the file descriptor of stderr , and this example redirects it to /dev/null . What this means in simple terms: ignore error output from the command.

What is the null command?

The null command is a THEN or ELSE command that is not followed by a command continuation character. If THEN or ELSE is not followed by either a continuation character or by a command in the same record, the THEN or ELSE results in no action.

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 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.

Can you tail dev Null?

To answer your question under what circumstances tail -f /dev/null might finish and therefore continue to the next line in something like a shell script: /dev/null (as with everything in Linux) is a file. When executing tail onto any file, the file must be opened using a filedescriptor.

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.

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