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".
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
echo foo > $(tty) in a script and run ./test.sh &> /dev/null - The output is still printed to the terminal. Of course this is not a problem if you're writing a script which uses no such commands.
/dev/null exists in Cygwin, you don't need to use nul.
Something like
script > /dev/null 2>&1
This will prevent standard output and error output, redirecting them both to /dev/null.
2>/dev/nullAn 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
Try
: $(yourcommand)
: is short for "do nothing".
$() is just your command.
0 (success). Let's see an example using command false that always returns 1 (failure). For instance ( echo foo | tee file ; false ) && echo bar displays foo. Using your trick to suppress the output: ( : $(echo foo | tee file ; false) ) && echo bar. But it displays bar meaning the return status code is 0 (this is not the returned status code from false). Please update your answer providing this limitation. Cheers
DUMMY=$(yourcommand)? It do not have the limitation you have mentioned. :)DUMMY=$( echo foo | tee file ; false ) && echo bar does not display anything. And the command DUMMY=$( echo foo | tee file ; true ) && echo bar displays bar. Let me know if your provide an answer to upvote it ;-) Cheers
command | : which maybe easier to typeLike 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
> nul on Windows with cygwin or git bash and now you are stuck with a nul file that can't be deleted, please do give a try to this answer, it worked like a charm.This is another option
scriptname |& :
: discards its input, so it works like /dev/null, but you are needlessly creating a pipe where none is necessary or useful.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
>&- closes the filedescriptor without even redirecting to /dev/null
foo 2>&- >&-
Can close stdin too
foo 2>&- >&- <&-
If you're running a command in the background and want to suppress its output, the syntax is the following:
(my_command > /dev/null &)
or
(my_command > /dev/null 2>&1 &)
2>&1 part, which is redirection of stderr to stdout. The first command will only suppress stdout but not stderr; the 2nd will suppress both.
I know this question is 15 years old, but it's the top result for searches for preventing output from a script, and there is (to my mind, at least) no valid answer given. The question specifically asks for something similar to the Windows "echo off" command. "echo off" is a command that is (or at least was, in the old cmd.com days) often put at the top of the script. It's a way to silence the script FROM WITHIN THE SCRIPT itself. All of the answer here seem to be addressing silencing the script from the command line when you run it, or silencing the output of specific lines within the script. I was looking for a way to silence all output from the script from within the script, and that's not found here.
The answer I found was to put this at the top of the script:
exec > /dev/null 2>&1
and at the bottom:
exec &>/dev/tty
Obviously, this prevents any errors from being seen and isn't appropriate for all use cases. If the script fails before restoring output in a session, you would see no output until you manually restored it.
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
>>)?