Questions tagged [stderr]
Standard error is another output stream typically used by programs to output error messages or diagnostics.
222
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Questions on shell redirection [duplicate]
I am studying for my RHCSA and already have my Linux+ and I'm trying to better understand shell redirection beyond just understanding the basic use cases and I am trying to grasp it at a deeper ...
- 9
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34
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Exporting Python's script errors/traceback to file with netcat
I have a Python script accessible with netcat: nc 'serverIP' port.
The Python script awaits an input from the user. If the input is expected, the script keeps running. If the input is unexpect (e.g. ...
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0
answers
51
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Xauthority file does not exist - so what?
I run X11 programs on a Linux host, displaying remotely on a Mac running the XQuartz X11 server. First of all, this is all on my private LAN so I don't need to tunnel the X connection through SSH, and ...
- 442
0
votes
1
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34
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linux contextually process stderr only if present
I want to only have a process called if there actually is a STDERR present, but I don't know how to evaluate if one is actually present or not. This code:
errtest() {
kubectl get namespace -A
...
- 1,195
0
votes
2
answers
34
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Bash receive stderr from a pipe which did not redirect it
Is it possible to receive/redirect the stderr of foo.sh from within bar.sh if called without redirecting it first: foo.sh | bar.sh?
foo.sh
#!/bin/bash
echo "hello world" >&2
bar.sh
#!...
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0
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63
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BASH - Getting stderr message into a variable to be passed to a trap
My question is relative to Ubuntu 20.04 where I am performing these tasks.
I currently pass some state information to a debug trap such as $BASH_COMMAND, $LINENO and $?. I would like to pass any ...
user516113
1
vote
1
answer
48
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can't get 2> to work on g++ command line on Ubuntu update
On a remote server that was updated with a newer version of Ubuntu, when I try to redirect stderr it won't work. Using putty from windows, but I've done it on the old server all the time.
g++ ...
- 175
0
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3
answers
76
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Using `1>&- 2>&- &' as an alias after a shell command
To run a program with bash in background, with no text output, it is possible to use: 1>&- 2>&- &. I would like to define an alias for this. However, if I write in .bashrc
alias ...
- 4,493
0
votes
1
answer
87
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Why isn't "Permission denied" in stderr? [duplicate]
I have a command: mywritercmd -f /tmp/test 2>&1 > log.txt I run in a bash terminal, the command returns error: could not open output file "/tmp/test": Permission denied
...
- 432
1
vote
1
answer
112
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Making Bash send this error to std error
While writing some Lua as a backend for my LuaTeX code I noticed the following. For background, here is the Lua code. This version is standard Lua. But you don't really need to understand Lua to ...
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2
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155
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Capture stdout of a crashing program and shell's "segfault error" message
I have a compiled program main.bin that is supposed to print:
hello world
another line
This program generates a segmentation fault right after printing the first line.
If I run it in the shell (zsh), ...
- 303
0
votes
0
answers
19
views
Get Percentage of used memory in Solaris [duplicate]
I wish to get Percentage of used memory in Solaris as non-root user.
The solution proposed here does not work for me and I get error.
$ /usr/sbin/prtconf 2>/dev/null | /usr/bin/awk '/Memory/ {print ...
- 297
0
votes
1
answer
104
views
Does redirected stderr remain unbuffered in bash?
{
echo bla1
echo bla2 1>&2
} >>myfile 2>&1
Is there any difference between the two echo-s?
The only difference I can think of, if echo bla2 2>&1 retains the unbuffered ...
- 411
0
votes
2
answers
126
views
How to capture output that is going neither to stdout nor to stderr?
As far as I can tell, some of the output generated by the command /usr/bin/modulecmd goes neither to stdout nor stderr, as illustrated by the following example:
% /usr/bin/modulecmd bash help null >...
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-1
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1
answer
60
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What type of buffering does stderr use by default (in linux)?
What type of buffering does the standard error stream use by default in Linux?
0
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1
answer
92
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Why is this shell output cannot be written to a file? [duplicate]
I'm working on a linux pinephone script that would launch a touchpad emulator. In order to do so, I need to compare the output string of:
./TouchpadEmulator /dev/input/event2 /dev/input/event1
once I ...
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0
answers
51
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How order of saving data redirected from stdout and stderr streams works?
I'm experimenting with redirecting and I've noticed some problem.
I know that when I want to save stdout data and stderr data in the same file I can just use 2>&1 or shorten >& like:
ls ...
- 181
2
votes
1
answer
62
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Redirecting output from within disk operations does not work
I am not able to successfully redirect STDOUT+STDERR on commands that operates with disks. Standard redirecting which always works, is somehow now catching the output. Two practical examples:
Example ...
1
vote
1
answer
50
views
bash I/O redirection - how to append to stderr
I have a script that loops over some big collection of data and performs some lenghty operations. Then i need to sort | uniq -c its output. So to let it know that its alive, I print a dot every N ...
- 153
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0
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241
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RuntimeError: 'v4l2loopback' backend: std::exception
I'm getting above error when I'm trying to execute following piece of code:
import pyvirtualcam
import numpy as np
with pyvirtualcam.Camera(width=1280, height=720, fps=20) as cam:
print(f'Using ...
- 1
0
votes
1
answer
84
views
process hangs after redirecting stderr using exec
I want to redirect stdout and stderr to 2 pipes one for each
to create the pipes I used:
mkfifo -m 0666 /var/run/log_stdout.pipe
mkfifo -m 0666 /var/run/log_stderr.pipe
and it works fine, but ...
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1
vote
1
answer
101
views
How to check if command had any output (zsh)
I want to print a new line after a command if it had any output (I hope that this will make it more readable once my terminal starts scrolling).
I found this:
precmd() {
precmd() {
print &...
- 299
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0
answers
458
views
Where does stdout and stderr go in the background
When processes get executed in the background, for example by using systemd to start the processes at startup, why doesn't the stdout and stderr still appear on the terminal when we access the ...
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1
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48
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how to get split commands output to file
I want to print output of below command to file, can you help me I tried 2>&1 even 2>> also
dd if=/dev/random bs=1 count=1000 status=progress |split -b 10 -a 10
I have other dd command ...
- 29
0
votes
1
answer
141
views
Redirect systemd service STDERR to command (sendmail)
This seems like something that's been asked before but I can't find it anywhere.
I have a systemd service that runs on a timer, updating my packages. I want to get emailed using ssmtp every time the ...
- 197
1
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0
answers
64
views
How to get stderr separate from stdout in task-spooler jobs
I am trying to get a separate output file for stderr for jobs sent to task-spooler on Ubuntu 20.04.
This command works fine:
tsp -Lfetcher sh -c 'curl -v https://google.com'
But I am having trouble ...
- 196
0
votes
2
answers
516
views
redirect stdout and stderr to null in the middle of a chain of '&&'s
TL;DR
I've researched this, and you can see what I've found in the More Details and My Attempts section.
My command is
date && echo "hi 1" && echo "1/0" | bc >/...
- 222
2
votes
1
answer
203
views
Additional file descriptor for debugging and piped output (logging, metrics, etc)
For a bash script project, I write human-readable log info to stdout/stderr. Additionally, I want to write formatted metrics to a third stream that will be discarded by default but can be redirected ...
- 23
1
vote
1
answer
154
views
Send debug output to terminal multiplexer
Given a shell script (bash in this example), one can use the set -x or -x passed to bash or other supporting shells to generate debug output.
I know how to redirect said output to a file ./script.sh 2&...
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3
votes
1
answer
720
views
Separate stdout and stderr for `docker run`?
Can I get separate stdout and stderr pipes for docker run?
Example:
$ docker run --rm -it alpine sh -c 'echo this is stdout; echo this is stderr >&2' \
2> stderr.txt
this is stdout
this is ...
- 4,843
-4
votes
2
answers
190
views
Standard error to standard output - is there other options beside redirection?
I have very limited understanding about standard error and standard output...
One of the common methods is to redirect standard error to standard output. Does it mean that error (which usually goes to ...
user435564
0
votes
1
answer
4k
views
Issue passing newline `\n` character to curl command
My Jenkins multiline parameter is read in a variable SERVER_IP which is passed to Unix curl command as below:
The curl command triggers a webpage(Jenkins Build) and passes the parameters to the ...
- 297
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1
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733
views
How to stop stderr output from gcloud command in cron script without stopping all error output?
I have a bash script for a cron job that uses Google Cloud SDK's gcloud command after some conditional statements.
eg.
gcloud compute firewall-rules update allow-ssh --source-ranges=$(echo "${...
- 924
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1
answer
130
views
Redirect standard error during concatenate using cat
Need some help on redirecting error to stdout for the below command
find /mypath/env/test/ -name "*.tmp" -exec cat '{}' ';' >> /mypath/env/final/merged.txt 2>&1
This command ...
- 135
1
vote
1
answer
89
views
What does "export >/dev/stderr" mean?
I've found in a bash script following line:
export >/dev/stderr
what does it mean?
- 443
1
vote
3
answers
1k
views
Can a program output to STDERR and still return a zero exit status?
I'm working on refactoring some Python scripts intended to be run from the command line. The scripts use logging, which makes some messages be written to STDERR (among other things). I wonder if it's ...
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-1
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3
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How does > /dev/null 2>&1 work? [duplicate]
I understand how redirecting output with > /dev/null causes it not to print to screen.
But for some reason this is not always enough, and some things still do get printed.
In those cases > /...
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13
votes
1
answer
4k
views
POSIX compliant way to redirect stdout and stderr to a file [duplicate]
I am trying to write a script which is POSIX compliant, so it can run on any *nix system (Debian, Fedora, CentOS, AIX, Arch... ALL of them). When it comes to redirection, I am rather confused on what ...
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2
votes
1
answer
82
views
How do I debug why stderr is being suppressed?
Running some shell functions and ctrl-c-ing them leads to my stderr being suppressed, such that echo hi >&2 and echo hi > /dev/stderr print nothing. I want to debug this, but I have no idea ...
- 1,287
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votes
1
answer
632
views
How to redirect this "Floating point exception(core dumped)" error?
I want to redirect the output of a program to a file with variable name and, at the same time, redirect the possible error. This is the script so far:
#!/bin/bash
echo "Se ejecutará el PET-linux.x ...
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3
answers
298
views
Which processes have standard file descriptors?
Which is the correct statement?
Every Unix process has the standard file descriptors open: standard input, standard output and standard error.
or
Every Unix process attached to a terminal has ...
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1
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28
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bash won't exit on error if a program's output is redirected to log file
#!/bin/bash
exec 200>/var/lock/scraper || exit 1
flock -n 200 || exit 1
cd /home/ubuntu/web_scraper
/home/ubuntu/.nvm/versions/node/v13.12.0/bin/node mongo/scraper.js > logs/scraper.log
...
0
votes
1
answer
338
views
Terminal and Grepping Stderr: how do I run a verbose code and grep the standard error without changing anything else?
Suppose I have a code, and it is running in a very verbose mode. This maximum verbosity exposes a message that I'd like to read to see how everything is doing. However, the terminal is flooded with ...
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1
vote
4
answers
2k
views
Reading from stderr in c
This is my c program read from stderr i write
#include <uninstd.h>
#include <stdio.h>
int main(void) {
char buff[3];
read(2, buff, sizeof(buff));
printf("%s", buff");
return 0;
}
My ...
1
vote
1
answer
207
views
Is it possible to write an alias or function in Bash to filter out the errors (stderr)?
I sometimes would do
grep -ri foo .
but in some node_modules, it could have some links to places that don't exist. So I can do a
grep -ri foo . 2>&-
or
grep -ri foo . 2> /dev/null
but ...
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2
votes
1
answer
237
views
A program's output seems to be neither stdout nor stderr? [duplicate]
I got a program vsftpd which output doesn't seem to be either stdout or stderr (if that's even possible?)
My terminal output is:
~# vsftpd
500 OOPS: SSL: cannot load RSA private key
I tried to ...
- 530
2
votes
1
answer
662
views
Stdout / stderr redirection doesn't work at preventing /dev/tcp/host/port redirection errors
This is normal redirection.
user@linux:~$ randomcommand
randomcommand: command not found
user@linux:~$
2>
user@linux:~$ randomcommand 2> /dev/null
user@linux:~$
&>
user@linux:~$ ...
user264359
0
votes
0
answers
277
views
Print clang include path and store in file
I'm writing a program that needs to pull in the clang include paths. Thanks to Dump include paths from g++ I'm half-way there. The command I'm using is:
clang++ -E -x c++ - -v < /dev/null
The ...
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1
answer
171
views
Use 2>&1 to direct stdout/stderr for a single command only among many in a BASH script
My first post, please be kind :)
I'm writing my first ever BASH script, and using systemd to invoke it on a timer (my first systemd units too!). The script runs backups daily, and uses notify-send to ...
- 23
2
votes
1
answer
555
views
How to redirect stderr in busybox?
I have
BusyBox v1.27.1 (2017-08-03 03:14:35 CEST) built-in shell (ash)
on router. I found a weird issue:
root@DD-WRT:/# echo -n "Hi" 2>/dev/null
-sh: 2: Invalid argument
Seems I cannot redirect ...
- 124