How do I redirect only stderr to dev Null?

In Unix, how do I redirect error messages 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 >/ 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 .

How do I redirect everything to dev Null?

Redirect All Output to /dev/null There are two ways to do this. The string >/dev/null means “send stdout to /dev/null,” and the second part, 2>&1 , means send stderr to stdout. In this case you have to refer to stdout as “&1” instead of simply “1.” Writing “2>1” would just redirect stdout to a file named “1.”

What is dev Null in shell script?

/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 do you use to forward errors to a null?

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. /dev/null is the standard Linux device where you send output that you want ignored.

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.

What is 2 >/ dev null in Unix?

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.

Why do we use 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.

Can you tail dev null?

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.

What do you use to forward errors to a file?

2 Answers

1. Redirect stdout to one file and stderr to another file: command > out 2>error.
2. Redirect stdout to a file ( >out ), and then redirect stderr to stdout ( 2>&1 ): command >out 2>&1.

Why does stderr redirect to / dev / null?

STDERR redirects to THE ADDRESS of STDOUT (File descriptor 1 in that moment, or /proc/self/fd/1), and then STDOUT redirects to /dev/null , but STDERR keeps redirecting to fd1!! As a result the normal output from STDOUT is discarded, but the errors coming from STDERR are still being written onto the console.

How to set stdout to / dev / null?

Well, that’s because you can’t. STDOUT and STDERR are just two files, represented by file descriptors, which are just integers, specifically 1 and 2. What you’re asking is to set descriptor 2 to /dev/null, then set descriptor 3 to the same file descriptor 2 and have that output go somewhere else.

What does 2 > / dev / null mean in the command line?

In short, it redirects stderr (fd 2) to the black hole (discards the output of the command). Run command and append stdout and stderr to a log file. Is there a good reason to use > /dev/null 2>&1 instead of &> /dev/null? – Craig McQueen Nov 30 ’15 at 6:43

How to send output 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. The syntax discussed below works with Bourne-like shells, such as sh, ksh, and bash: