Apologize if this is a really simple question, but I couldn't find anything on google for "redirect stdout and stderr to bash script" and "redirect bash script output to another bash script".
I know this will redirect stdout and stderr to log.txt, but I'm not sure how to redirect it to a bash script.
java -jar build/libs/bot-kt-1.1.3.jar > log.txt 2>&1
Ideally something that behaves like above and is like so
java -jar build/libs/bot-kt-1.1.3.jar > "./script.sh" 2>&1 # script.sh uses the $1 argument for input
You can use xargs to move data from a pipe into an argument:
java -jar build/libs/bot-kt-1.1.3.jar 2>&1 | xargs ./script.sh
to pass everything as a single argument:
java -jar build/libs/bot-kt-1.1.3.jar 2>&1 | xargs --null ./script.sh
You can use command substitution for that:
./script.sh $(java -jar build/libs/bot-kt-1.1.3.jar 2>&1)
In addition to perreal's answer, if your script could be changed to read from stdin instead of expecting a parameter, you could also use a pipe:
java -jar build/libs/bot-kt-1.1.3.jar 2>&1 | ./script.sh
Related
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
Something like
script > /dev/null 2>&1
This will prevent standard output and error output, redirecting them both to /dev/null.
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
Try
: $(yourcommand)
: is short for "do nothing".
$() is just your command.
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
This is another option
scriptname |& :
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 $(find / -name core) &> /dev/null
That said, you can use this simple redirection:
/path/to/command &>/dev/null
In your script you can add the following to the lines that you know are going to give an output:
some_code 2>>/dev/null
Or else you can also try
some_code >>/dev/null
I want to copy stdout to a log file from within a bash script, meaning I don't want to call the script with output piped to tee, I want the script itself to handle it. I've successfully used this answer to accomplish this, using the following code:
#!/bin/bash
exec > >(sed "s/^/[${1}] /" | tee -a myscript.log)
exec 2>&1
# <rest of script>
echo "hello"
sleep 10
echo "world"
This works, but has the downside of output being buffered until the script is completed, as is also discussed in the linked answer. In the above example, both "hello" and "world" will show up in the log only after the 10 seconds have passed.
I am aware of the stdbuf command, and if running the script with
stdbuf -oL ./myscript.sh
then stdout is indeed continuously printed both to the file and the terminal.
However, I'd like this to be handled from within the script as well. Is there any way to combine these two solutions? I'd rather not resort to a wrapper script that simply calls the original script enclosed with "stdbuf -oL".
You can use a workaround and make the script execute itself with stdbuf, if a special argument is present:
#!/bin/bash
if [[ "$1" != __BUFFERED__ ]]; then
prog="$0"
stdbuf -oL "$prog" __BUFFERED__ "$#"
else
shift #discard __BUFFERED__
exec > >(sed "s/^/[${1}] /" | tee -a myscript.log)
exec 2>&1
# <rest of script>
echo "hello"
sleep 1
echo "world"
fi
This will mostly work:
if you run the script with ./test, it shows unbuffered [] hello\n[] world.
if you run the script with ./test 123 456, it shows [123] hello\n[123] world like you want.
it won't work, however, if you run it with bash test - $0 is set to test which is not your script. Fixing this is not in the scope of this question though.
The delay in your first solution is caused by sed, not by tee. Try this instead:
#!/bin/bash
exec 6>&1 2>&1>&>(tee -a myscript.log)
To "undo" the tee effect:
exec 1>&6 2>&6 6>&-
I run the following command in shell:
sh myscript.sh > test.txt
The output is displayed on shell. I was expecting that the output would be put into test.txt.
The output isn't displayed on the shell, instead it's the STDERR that's displayed on the shell.
If you want both the STDOUT and STDERR to be redirected to the log file, say:
sh myscript.sh > test.txt 2>&1
Since you've tagged the question bash, you could also say:
bash myscript.sh >& test.txt
Printed output maybe be standard error output.
Using following, you can also redirect standard error (file descriptor 2):
sh myscript.sh > test.txt 2>&1
In bash, you can also use following forms:
sh myscript.sh &> test.txt # This is preferred according to bash(1).
sh myscript.sh >& test.txt
I'm looking for a solution (similar to the bash code below) to copy both stdout and stderr to a file in addition to the screen within ksh on Solaris.
The following code works great in the bash shell:
#!/usr/bin/bash
# Clear the logfile
>logfile.txt
# Redirect all script output to a logfile as well as their normal locations
exec > >(tee -a logfile.txt)
exec 2> >(tee -a logfile.txt >&2)
date
ls -l /non-existent/path
For some reason this is throwing a syntax error on Solaris. I assume it's because I can't do process substitution, and I've seen some posts suggesting the use of mkfifo, but I've yet to come up with a working solution.
Does anyone know of a way that all output can be redirected to a file in addition to the default locations?
Which version of ksh are you using? The >() is not supported in ksh88, but is supported in ksh93 - the bash code should work unchanged (aside from the #! line) on ksh93.
If you are stuck with ksh88 (poor thing!) then you can emulate the bash/ksh93 behaviour using a named pipe:
#!/bin/ksh
# Clear the logfile
>logfile.txt
pipe1="/tmp/mypipe1.$$"
pipe2="/tmp/mypipe2.$$"
trap 'rm "$pipe1" "$pipe2"' EXIT
mkfifo "$pipe1"
mkfifo "$pipe2"
tee -a logfile.txt < "$pipe1" &
tee -a logfile.txt >&2 < "$pipe2" &
# Redirect all script output to a logfile as well as their normal locations
exec >"$pipe1"
exec 2>"$pipe2"
date
ls -l /non-existent/path
The above is a second version to enable stderr to be redirected to a different file.
How about this:
(some commands ...) 2>&1 | tee logfile.txt
Add -a to the tee command line for subsequent invocations to append rather than overwrite.
In ksh, the following works very well for me
LOG=log_file.$(date +%Y%m%d%H%M%S).txt
{
ls
date
... whatever command
} 2>&1 | tee -a $LOG
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
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
Redirect stderr to stdout
This will redirect the stderr (which is descriptor 2) to the file descriptor 1 which is the the stdout.
2>&1
Redirect stdout to File
Now when perform this you are redirecting the stdout to the file sample.s
myprogram > sample.s
Redirect stderr and stdout to File
Combining the two commands will result in redirecting both stderr and stdout to sample.s
myprogram > sample.s 2>&1
Redirect stderr and stdout to /dev/null
Redirect to /dev/null if you want to completely silent your application.
myprogram >/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 &>-
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 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
Try with:
myprogram &>/dev/null
to get no output
Useful variations:
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):
stty -echo && ./programMightNotExist 2> errors.log && stty echo
Detach completely and silence everything, even killing the parent
script won't abort ./prog (Does behave just like nohup):
./prog </dev/null >/dev/null 2>&1 &
nohup can be used as well to fully detach, as follow:
nohup ./prog &
A log file nohup.out will be created aside of the script, use tail -f nohup.out to read it.
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
For output only on error:
so [command]