How to hide command output in Bash

Question

I want to make my Bash scripts more elegant for the end user. How do I hide the output when Bash is executing commands?

For example, when Bash executes

yum install nano

The following will show up to the user who executed the Bash:

Loaded plugins: fastestmirror
base                                                     | 3.7 kB     00:00
base/primary_db                                          | 4.4 MB     00:03
extras                                                   | 3.4 kB     00:00
extras/primary_db                                        |  18 kB     00:00
updates                                                  | 3.4 kB     00:00
updates/primary_db                                       | 3.8 MB     00:02
Setting up Install Process
Resolving Dependencies
--> Running transaction check
---> Package nano.x86_64 0:2.0.9-7.el6 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

================================================================================
 Package         Arch              Version                Repository       Size
================================================================================
Installing:
 nano            x86_64            2.0.9-7.el6            base            436 k

Transaction Summary
================================================================================
Install       1 Package(s)

Total download size: 436 k
Installed size: 1.5 M
Downloading Packages:
nano-2.0.9-7.el6.x86_64.rpm                              | 436 kB     00:00
warning: rpmts_HdrFromFdno: Header V3 RSA/SHA256 Signature, key ID c105b9de: NOKEY
Retrieving key from file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6
Importing GPG key 0xC105B9DE:
 Userid : CentOS-6 Key (CentOS 6 Official Signing Key) <[email protected]>
 Package: centos-release-6-4.el6.centos.10.x86_64 (@anaconda-CentOS-201303020151.x86_64/6.4)
 From   : /etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
  Installing : nano-2.0.9-7.el6.x86_64                                      1/1
  Verifying  : nano-2.0.9-7.el6.x86_64                                      1/1

Installed:
  nano.x86_64 0:2.0.9-7.el6

Complete!

Now I want to hide this from the user and instead show:

    Installing nano ......

How can I accomplish this task? I will definitely help to make the script more user friendly. In case an error occurs then it should be shown to the user.

I would like to know how to show same message while a set of commands are being executed.

echo "Installing nano ......"; yum install nano &> /dev/null — user000001
– user000001, Commented Aug 5, 2013 at 16:12
Possible duplicate of How to suppress all output from a command using Bash? — Ulrich Eckhardt
– Ulrich Eckhardt, Commented Aug 26, 2019 at 6:08

Jeff Bowman · Accepted Answer · 2016-07-07 19:32:50Z

Use this.

{
  /your/first/command
  /your/second/command
} &> /dev/null

Explanation

To eliminate output from commands, you have two options:

Close the output descriptor file, which keeps it from accepting any more input. That looks like this:
```
your_command "Is anybody listening?" >&-
```
Usually, output goes either to file descriptor 1 (stdout) or 2 (stderr). If you close a file descriptor, you'll have to do so for every numbered descriptor, as &> (below) is a special BASH syntax incompatible with >&-:
```
/your/first/command >&- 2>&-
```
Be careful to note the order: >&- closes stdout, which is what you want to do; &>- redirects stdout and stderr to a file named - (hyphen), which is not what what you want to do. It'll look the same at first, but the latter creates a stray file in your working directory. It's easy to remember: >&2 redirects stdout to descriptor 2 (stderr), >&3 redirects stdout to descriptor 3, and >&- redirects stdout to a dead end (i.e. it closes stdout).

Also beware that some commands may not handle a closed file descriptor particularly well ("write error: Bad file descriptor"), which is why the better solution may be to...
Redirect output to /dev/null, which accepts all output and does nothing with it. It looks like this:
```
your_command "Hello?" > /dev/null
```
For output redirection to a file, you can direct both stdout and stderr to the same place very concisely, but only in bash:
```
/your/first/command &> /dev/null
```

Finally, to do the same for a number of commands at once, surround the whole thing in curly braces. Bash treats this as a group of commands, aggregating the output file descriptors so you can redirect all at once. If you're familiar instead with subshells using ( command1; command2; ) syntax, you'll find the braces behave almost exactly the same way, except that unless you involve them in a pipe the braces will not create a subshell and thus will allow you to set variables inside.

{
  /your/first/command
  /your/second/command
} &> /dev/null

See the bash manual on redirections for more details, options, and syntax.

Hi, I know it's an old question but can the same be done conditionally? Like I want to hide the output under certain condition? I know I can replicate the same part under if-else but is there a better way to do so?
@UsamaZafar I would do that by setting a variable ("shell parameter"), which you set to either /dev/null or /dev/stdout (or /path/to/a/logfile) conditionally earlier in the script, and then redirecting to that destination by using &> $output_dest (or whatever you name it). If you don't want to combine stdout and stderr in that case, you could redirect them separately like > $output_dest 2> $errors_dest.
What if I have command && command? Do I have to append &>/dev/null after each command?
@Rafs Yes. Note in bash that echo A && echo B &> /dev/null shows "A". Braces work for it though, like { echo A && echo B; } &> /dev/null. The semicolon is necessary if you don't have a line break before the } as I do in the post.

ktm5124 · Accepted Answer · 2013-08-05 16:34:12Z

51

You can redirect stdout to /dev/null.

yum install nano > /dev/null

Or you can redirect both stdout and stderr,

yum install nano &> /dev/null.

But if the program has a quiet option, that's even better.

edited Aug 5, 2013 at 16:34

answered Aug 5, 2013 at 16:14

ktm5124

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Comments

LeOn - Han Li · Accepted Answer · 2022-06-15 16:32:05Z

40

A process normally has two outputs to screen: stdout (standard out), and stderr (standard error).

Normally informational messages go to sdout, and errors and alerts go to stderr.

You can turn off stdout for a command by doing

MyCommand >/dev/null

and turn off stderr by doing:

MyCommand 2>/dev/null

If you want both off, you can do:

MyCommand >/dev/null 2>&1

The 2>&1 says send stderr to the same place as stdout.

edited Jun 15, 2022 at 16:32

answered May 31, 2017 at 16:10

LeOn - Han Li

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1 Comment

Brad Over a year ago

The suggestion for suppressing both doesn't work for me. But this does > /dev/null 2>&1

Giuseppe Pes · Accepted Answer · 2013-08-05 16:26:16Z

You can redirect the output to /dev/null. For more info regarding /dev/null read this link.

You can hide the output of a comand in the following ways :

echo -n "Installing nano ......"; yum install nano > /dev/null; echo " done.";

Redirect the standard output to /dev/null, but not the standard error. This will show the errors occurring during the installation, for example if yum cannot find a package.

echo -n "Installing nano ......"; yum install nano &> /dev/null; echo " done.";

While this code will not show anything in the terminal since both standard error and standard output are redirected and thus nullified to /dev/null.

Great share ....dude can you show me how to output the same message only once for a set of commands

Quanlong · Accepted Answer · 2015-06-16 16:16:24Z

6

>/dev/null 2>&1 will mute both stdout and stderr

yum install nano >/dev/null 2>&1

answered Jun 16, 2015 at 16:16

Quanlong

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Comments

kkeller · Accepted Answer · 2014-02-25 22:02:54Z

4

You should not use bash in this case to get rid of the output. Yum does have an option -q which suppresses the output.

You'll most certainly also want to use -y

echo "Installing nano..."
yum -y -q install nano

To see all the options for yum, use man yum.

answered Feb 25, 2014 at 22:02

kkeller

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1 Comment

Hyperion Over a year ago

Thanks, I assumed yum had one since apt-get used -qq as well to suppress. This was helpful for what I am doing.

DeanSinaean · Accepted Answer · 2021-04-20 13:51:05Z

0

you can also do it by assigning its output to a variable, this is particularly useful when you don't have /dev/null.

Yes, I came across a situation when I can't use /dev/null.

The solution I found was to assign the output to a variable which I will never use there after:

hide_output=$([[ -d /proc ]] && [[ mountpoint -q /proc ]] && umount -l /proc)

answered Apr 20, 2021 at 13:51

DeanSinaean

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Comments

Brad · Accepted Answer · 2022-03-11 06:56:34Z

0

This: command > /dev/null Or this: (to suppress errors as well) command > /dev/null 2>&1

Similar to lots of other answers but they didn't work for me with 2> being in front of dev/null.

answered Mar 11, 2022 at 6:56

Brad

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