Standard error is another output stream typically used by programs to output error messages or diagnostics.

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53
votes
6answers
7k views

Can I configure my shell to print STDERR and STDOUT in different colors?

I want to set my terminal up so stderr is printed in a different color than stdout; maybe red. This would make it easier to tell the two apart. Is there a way to configure this in .bashrc? If not, is ...
13
votes
3answers
784 views

When to use redirection to stderr in shell scripts

I know that well-behaved utilities like grep output "normal" messages to stdout, and error messages to stderr. $ grep '^foo' file1 file2 file1:foo grep: file2: No such file or directory When I'm ...
11
votes
2answers
5k views

Does `Segmentation fault` message come under STDERR?

I ran an executable in bash ./code > log It shows occasional error messages on terminal whereas all printf statements go into log file. I re-run it like below ./code >& log Now, the ...
10
votes
2answers
3k views

stderr over ssh -t

This sends output to STDERR, but does not propagate Ctrl+C (i.e. Ctrl+C will kill ssh but not the remote sleep): $ ssh localhost 'sleep 100;echo foo ">&2"' This propagates Ctrl+C (i.e. Ctrl+...
9
votes
1answer
757 views

Output of command not in stderr nor stdout

I've stumbled on this issue, so I'm wondering how is this possible? Standard run of command: # zabbix_sender -c zabbix_agentd.conf -k mmysql.QCInserts -o 14 info from server: "Processed 0 Failed 1 ...
8
votes
2answers
25k views

nohup: ignoring input and redirecting stderr to stdout

I am starting my application in the background using nohup as mentioned below - root@phx5qa01c:/bezook# nohup java -jar ./exhibitor-1.5.1/lib/exhibitor-1.5.1-jar-with-dependencies.jar -c file --...
7
votes
3answers
530 views

How to run a command while logging output to a file?

I have a console application that needs to be run as part of the deployment of a new application version on my server. This console application is designed to output to the console, and cannot be ...
7
votes
1answer
319 views

How can I pipe only stderr in zsh?

In bash: $ echo hi 2>&1 1>/dev/null | cat $ While in zsh: $ echo hi 2>&1 1>/dev/null | cat hi $ Is there a way to pipe only standard error while redirecting standard out?
7
votes
2answers
328 views

Redirecting standard error output to bash variable

Here's a C code snippet that will cause segfault: // segfault.c #include <string.h> int main() { memset((char *)0x0, 1, 100); return 1; } Compile it with: gcc segfault.c -o ...
6
votes
1answer
285 views

Is it possible to create sticky redirection from stdout/stderr

Consider such code: echo hello >> log.txt echo world >> log.txt I execute command with stdout redirection. Is it possible to create sticky redirection? Something like this: redir ...
6
votes
1answer
265 views

Can redirecting stdout and stderr to the same file mangle lines?

I've read that when redirecting stdout and stderr to the same file using 2>&1, stdout is usually block buffered while stderr is unbuffered. If a very long line is written to stdout, requiring ...
5
votes
2answers
10k views

How can I filter those “Permission denied” from find output? [duplicate]

I started using sed recently. One handy way I use it is to ignore unimportant lines of a log file: tail -f example.com-access.log | sed '/127.0.0.1/d;/ELB-/d;/408 0 "-" "-"/d;' But when I try to ...
5
votes
3answers
549 views

sending output to /dev/stderr vs. >&2

In scripts, errors are usually sent to file descriptor 2 with &2, ie: echo "error" >&2 Sometimes /dev/stderr is used instead: echo "error" > /dev/stderr Looking at /dev/stderr, I ...
5
votes
3answers
10k views

stdin, stderr, redirection and logs

Is there a difference between those two lines ? /home/user/script.sh >> /home/user/stdout_and_error.log 2>&1 /home/user/script.sh 2>&1 >> /home/user/stdout_and_error.log ...
5
votes
4answers
419 views

A command that generates both standard error and output

I want to do some troubleshooting on my bash script. Is there a short and simple command that generates both stdout and stderr so that I can use 2>&1 on it? Sorry if this looks trivial, but I ...
5
votes
3answers
7k views

Copy stdout and stderr to a log file and leave them on the console within the script itself

Using bash, how do I copy stderr and stdout to a log file and also leave them displayed on the console? I would like to do this within the script itself using an exec. I tried with exec &>&...
5
votes
3answers
7k views

Write to stderr

I'm using stderred to color all output streamed to stderr red. It's working fine. But when I write my own bash script and throw an error with echo 'error' 1>&2, it doesn't color the output in ...
4
votes
3answers
194 views

Trying to make sense of bash redirection syntaxes and their outputs

I'm new to Linux and trying to understand how redirections work. I have been testing various syntaxes for redirecting stdout and stderr to the same file, which don't all produce the same results. ...
4
votes
2answers
2k views

Inconsistency of stderr redirection between tcsh and other shells

I'm running into issues with redirection in tcsh. Consider the following commands: vi --version and vi --xxx. And let's assume this is on a machine where vi supports the --version option. The ...
4
votes
2answers
15k views

How to redirect error to a file?

I have this simple script which redirects the output and append it to a file. filename="/home/ronnie/tmp/hello" date=$(date) echo "$date" >> $filename Now, lets suppose I change date=$(date) ...
4
votes
1answer
160 views

unexpected output with grep

I am using pyrit. For those who dont know, pyrit allows among other things to check if a wpa handshake key is valid: pyrit -r file0.cap analyze when a file does not contain a valid key, here is ...
4
votes
2answers
441 views

Redirect stderr of the double-parentheses construct

I'd like to be able to redirect the stderr of a double-parentheses construct. For example: a=$(($var/$var2)) would output some error messages if $var2 = 0, I do not want the user to see this. I ...
4
votes
0answers
37 views

Show error messages and information that a program was killed on another terminal [duplicate]

If I open a program, say evince, from the GNOME GUI, it is not attached to a terminal. If I send it a signal, it acts accordingly but nothing shows up in my terminal. If I were to open it in a ...
3
votes
2answers
8k views

suppress stderr messages in a bash script

Consider the following (slightly silly) script name 'test1.sh': #/bin/bash # sleep 10 & echo sleep pid = $! pkill sleep When I run it, I get not only the output of the echo, but bash's ...
3
votes
1answer
239 views

Why doesn't “cvs --help | less” work?

I don't know why, but piping cvs --help to less doesn't work. Probably it's because cvs --help outputs not to standard output(1) or error output(2), but somewhere else. Could you tell me where does it ...
3
votes
1answer
373 views

Why is it possible to refer to a closed stderr under bash?

I'd like to know why bash doesn't display an error message when we refer to a closed stderr. When it comes to other file descriptors, they have to be opened if we want to, for example, duplicate them. ...
3
votes
1answer
99 views

What is the relationship between a program's output, standard output, and its file descriptors?

Let's assume that I am running wget which is downloading something. It's printing some text to my terminal and writes the downloaded data into a file. From a terminology point of view, what is the ...
2
votes
2answers
389 views

stderr gets flushed before stdout, when using file logger

My python code: import sys print "i am a daemon" print "i will be run using nohup" sys.stderr.write("i am an error message inside nohup process\n") When i run the code as python a.py, it shows, i ...
2
votes
3answers
35 views

What is regarded as “ideal” in relation to using stdout/stderr for output in different situations?

I have seen stdout and stderr used in a variety of different ways - as far as I understand, it is common to use stdout for general information and stderr for errors and the like. However, I have also ...
2
votes
4answers
218 views

Can a running script identify the logging context?

Let us say I redirect the STDOUT, STDERR of a program to files. ./script.sh 1> output.log 2> error.log Can the running program find this out i.e. know the paths to these files?
2
votes
2answers
91 views

Different error messages when using different strings in terminal

When I insert, for example, unix.stackexchange.com followed by Enter in terminal, I get the following error: unix.stackexchange.com: command not found This is ok and as I expected. But when I insert ...
2
votes
2answers
92 views

Output is in console but not part of stdout or stderr

I have a command that outputs the following: READY Listening.... HELLO READY Listening.... TEST It is speech recognition from pocketsphinx_continuous. I need that output redirected to a file, and ...
2
votes
2answers
90 views

Output piped content to file and show number of lines in the file on stdout

I would like to use tee to pipe content from stdout and stderr respectively into files (in fact append it with > >(tee -a $filename)). However, instead of seeing the contents appended to the ...
2
votes
2answers
112 views

redirecting std output and std error

I have been trying to figure out the relationship between file descriptors. One thing I don't understand is, how is: ls -l /bin/usr > ls-output.txt 2>&1 different from: ls -l /bin/usr 2&...
2
votes
1answer
131 views

Stderr of piped shell scripts isn't always displayed

I piped my own shell scripts for some testing and accidentally noticed something strange. Namely, the stderr of those piped processes isn't always displayed on the screen. I simplified the scripts ...
2
votes
1answer
37 views

Unable to redirect stdout/stderr to log file [duplicate]

I have a script tmp.sh #!/bin/bash echo hello sleep 3 echo 3 I want to log the script running time (as well as script stdout) to a log file. user$ time ./tmp.sh >& log.tmp real 0m3....
2
votes
1answer
65 views

aptitude produces output twice

For quite a while, I get a double output of some messages from aptitude. Here’s an example: > sudo aptitude install mpw Couldn't find package "mpw". However, the following packages contain "mpw" ...
2
votes
1answer
111 views

Run a script when a process throws stderr message

I want to "wrap" a process around another to catch stderr messages when they occur. Use Case I'm using Compass and I have to have a terminal open and see if there is something wrong. My plan is to ...
1
vote
2answers
72 views

shell stderr to /dev/null

I have PID file and I want to get PID number so this is what I am doing. [root@linux ~]# PID=`cat /usr/local/foo/var/run/foo.pid` [root@linux ~]# echo $PID 3414 sometimes this file doesn't ...
1
vote
2answers
5k views

How do I suppress a warning message?

touch ~/deleted/$(echo "directory_"$(readlink -f foo)|tr '/' '\') 2> /dev/null where foo is a directory It's reading the full pathname of foo and creating it as a file replacing all '/' with '\' ...
1
vote
1answer
214 views

Pipe not picking up stdout

I am running a java program from a OS X 10.8 bash terminal, and are trying to rederect the output it is producing. However, when either running this throug a pipe, or rederecting it to a file, the ...
1
vote
2answers
13 views

redirect the output of {time}

I am trying to benchmark a single request agains a webserver, and am having a problem doing so, specifically, I am having an issue redirecting the output of the time command. If i simply run time ...
1
vote
2answers
2k views

Redirect grep error output to file

I wanted to capture to a file the errors being returned on the command line from grep. For example, grep foo.lookup No such file in directory I want to output that to a log file. This is my shell ...
1
vote
2answers
31 views

I want to catch the STDERR and STDOUT of Background running script

I have to run a script background and also i have to catch the STDERR and STDOUT . i'm using the below line . test.sh & >> log_file 2>&1 But un fortunately nothing is getting ...
1
vote
2answers
136 views

Duplicate stdin to stdout and stderr, but in a synchronized way

I need to duplicate the stdout of a producer and feed it to two consumer in a synchronized fashion. consumer 1 producer | duplicator | consumer 2 ...
1
vote
1answer
64 views

`docker logs foo | less` isn't searchable or scrollable but `docker logs foo 2>&1 | less` is

Using either one gives readable text. But only with the stderr redirect can one scroll or type /somepattern and get matches. Without it searching gives "Nothing to search (press RETURN)" and a ...
1
vote
0answers
20 views

Suppress warning of rbenv versions if no rubies installed

At the moment I'm working on Ansible role that installs ruby with rbenv. In order not to install same ruby version every time I run setup task I have to check that no needed ruby is already installed. ...
1
vote
2answers
144 views

CSH and all output (with errors) to file

I need save all output from compilation to file. I have many errors "undefined reference" and I want see all of these errors. I try "makeall >& out", but in file "out" aren't any of error "...
1
vote
1answer
125 views

capture log of ufsdump when backup to stdout

I am backing a file system with ufsdump. In order to gain space in the remote file system I backup to stdout then pipe the output to compress. I find is more efficient that backuping up and then ...
1
vote
1answer
138 views

Using find -exec and having trouble with redirecting standard error

I have an individual.sh script that pipes standard error to a grep command, like this: FOUND=$(tesseract "$i" out -psm 0 |& grep -ci 'Orientation in degrees: [^0]') If I run the script like ...