I have a program that outputs to stdout and would like to silence that output in a Bash script while piping to a file.
For example, running the program will output:
% myprogram
% WELCOME TO MY PROGRAM
% Done.
I want the following script to not output anything to the terminal:
#!/bin/bash
myprogram > sample.s
This question is related to
bash
Try with:
myprogram &>/dev/null
to get no output
This will redirect the stderr (which is descriptor 2) to the file descriptor 1 which is the the stdout.
2>&1
Now when perform this you are redirecting the stdout to the file sample.s
myprogram > sample.s
Combining the two commands will result in redirecting both stderr and stdout to sample.s
myprogram > sample.s 2>&1
Redirect to /dev/null
if you want to completely silent your application.
myprogram >/dev/null 2>&1
Note: This answer is related to the question "How to turn off echo while executing a shell script Linux" which was in turn marked as duplicated to this one.
To actually turn off the echo the command is:
stty -echo
(this is, for instance; when you want to enter a password and you don't want it to be readable. Remember to turn echo on at the end of your script, otherwise the person that runs your script won't see what he/she types in from then on. To turn echo on run:
stty echo
If you want STDOUT and STDERR both [everything], then the simplest way is:
#!/bin/bash
myprogram >& sample.s
then run it like ./script
, and you will get no output to your terminal. :)
the ">&" means STDERR and STDOUT. the &
also works the same way with a pipe: ./script |& sed
that will send everything to sed
If you are still struggling to find an answer, specially if you produced a file for the output, and you prefer a clear alternative:
echo "hi" | grep "use this hack to hide the oputut :) "
If it outputs to stderr as well you'll want to silence that. You can do that by redirecting file descriptor 2:
# Send stdout to out.log, stderr to err.log
myprogram > out.log 2> err.log
# Send both stdout and stderr to out.log
myprogram &> out.log # New bash syntax
myprogram > out.log 2>&1 # Older sh syntax
# Log output, hide errors.
myprogram > out.log 2> /dev/null
Useful in scripts:
Get only the STDERR in a file, while hiding any STDOUT even if the program to hide isn't existing at all (does not ever hang parent script), this alone was working:
stty -echo && ./programMightNotExist 2> errors.log && stty echo
Detach completely and silence everything, even killing the parent script won't abort ./prog
:
./prog </dev/null >/dev/null 2>&1 &
All output:
scriptname &>/dev/null
Portable:
scriptname >/dev/null 2>&1
Portable:
scriptname >/dev/null 2>/dev/null
For newer bash (no portable):
scriptname &>-
Source: Stackoverflow.com