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 -- gt  Running transaction check --- gt  Package nano x86 64 0 2 0 9-7 el6 will be installed -- gt  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   lt centos-6-key centos org gt   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

User · Answer

gt  dev null 2 gt  amp 1 will mute both stdout and stderr  yum install nano  gt  dev null 2 gt  amp 1

User · Answer

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  gt   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  amp  gt   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

User · Answer

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

User · Answer

SILENT    Type     SILENT    in the beginning of your script without colons

User · Answer

You can redirect stdout to  dev null   yum install nano  gt   dev null  Or you can redirect both stdout and stderr   yum install nano  amp  gt   dev null   But if the program has a quiet option  that s even better

User · Answer

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  gt  dev null   and turn off stderr by doing   MyCommand 2 gt  dev null   If you want both off  you can do   MyCommand 2 gt  amp 1  gt  dev null   The 2 gt  amp 1 says send stderr to the same place as stdout

User · Answer

Use this        your first command    your second command    amp  gt   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    gt  amp -   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  amp  gt   below  is a special BASH syntax incompatible with  gt  amp -    your first command  gt  amp - 2 gt  amp -   Be careful to note the order   gt  amp - closes stdout  which is what you want to do   amp  gt - 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   gt  amp 2 redirects stdout to descriptor 2  stderr    gt  amp 3 redirects stdout to descriptor 3  and  gt  amp - 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    gt   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  amp  gt   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    amp  gt   dev null   See the bash manual on redirections for more details  options  and syntax

[bash] How to hide command output in Bash

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