How can I suppress all output from a command using Bash?
BashShellScriptingEchoBash Problem Overview
I have a Bash script that runs a program with parameters. That program outputs some status (doing this, doing that...). There isn't any option for this program to be quiet. How can I prevent the script from displaying anything?
I am looking for something like Windows' "echo off".
Bash Solutions
Solution 1 - Bash
The following sends standard output to the null device (bit bucket).
scriptname >/dev/null
And if you also want error messages to be sent there, use one of (the first may not work in all shells):
scriptname &>/dev/null
scriptname >/dev/null 2>&1
scriptname >/dev/null 2>/dev/null
And, if you want to record the messages, but not see them, replace /dev/null with an actual file, such as:
scriptname &>scriptname.out
For completeness, under Windows cmd.exe (where "nul" is the equivalent of "/dev/null"), it is:
scriptname >nul 2>nul
Solution 2 - Bash
Something like
script > /dev/null 2>&1
This will prevent standard output and error output, redirecting them both to /dev/null.
Solution 3 - Bash
Try
: $(yourcommand)
: is short for "do nothing".
$() is just your command.
Solution 4 - Bash
An alternative that may fit in some situations is to assign the result of a command to a variable:
$ DUMMY=$( grep root /etc/passwd 2>&1 )
$ echo $?
0
$ DUMMY=$( grep r00t /etc/passwd 2>&1 )
$ echo $?
1
Since Bash and other POSIX commandline interpreters does not consider variable assignments as a command, the present command's return code is respected.
Note: assignement with the typeset or declare keyword is considered as a command, so the evaluated return code in case is the assignement itself and not the command executed in the sub-shell:
$ declare DUMMY=$( grep r00t /etc/passwd 2>&1 )
$ echo $?
0
Solution 5 - Bash
Like andynormancx' post, use this (if you're working in an Unix environment):
scriptname > /dev/null
Or you can use this (if you're working in a Windows environment):
scriptname > nul
Solution 6 - Bash
Take a look at this example from The Linux Documentation Project:
>3.6 Sample: stderr and stdout 2 file > >This will place every output of a program to a file. This is suitable sometimes for cron entries, if you want a command to pass in absolute silence. > rm -f $(find / -name core) &> /dev/null
That said, you can use this simple redirection:
/path/to/command &>/dev/null
Solution 7 - Bash
This is another option
scriptname |& :
Solution 8 - Bash
In your script you can add the following to the lines that you know are going to give an output:
some_code 2>>/dev/null
Or else you can also try
some_code >>/dev/null