Bash에서 명령 출력을 숨기는 방법

Bash에서 명령 출력을 숨기는 방법

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최종 사용자를 위해 bash 스크립트를 더 우아하게 만들고 싶습니다. bash가 명령을 실행할 때 출력을 숨기는 방법 예를 들어 bash가 실행될 때

yum install nano

다음은 bash를 실행 한 사용자에게 표시됩니다.

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) <centos-6-key@centos.org>
 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!

이제 사용자에게 이것을 숨기고 대신 표시하고 싶습니다.

Installing nano ......

이 작업을 어떻게 수행 할 수 있습니까? 스크립트를보다 사용자 친화적으로 만드는 데 확실히 도움이 될 것입니다. 오류가 발생하면 사용자에게 표시되어야합니다.

편집 명령 집합이 실행되는 동안 동일한 메시지를 표시하는 방법을 알고 싶습니다.

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이것을 사용하십시오.

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

설명

명령에서 출력을 제거하려면 두 가지 옵션이 있습니다.

• 더 이상 입력을받지 않도록 출력 설명자 파일을 닫습니다. 다음과 같이 보입니다.

  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.

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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.

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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 2>&1 >/dev/null

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

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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.

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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.

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

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

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.SILENT:

Type " .SILENT: " in the beginning of your script without colons.

참고URL : https://stackoverflow.com/questions/18062778/how-to-hide-command-output-in-bash