Bash Capture Error Message
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Bash Get Error Message
to the top How to capture error message from executed command? up vote 5 down vote favorite 1 I was tasked to create an automated server hardening script and one thing that they need is a report of all the output of each command executed. I want to store the error message inside a string and append it in a text file. Let's say I ran this command: /sbin/modprobe -n -v hfsplus The output of bash print error message running this in my machine would be: FATAL: Module hfsplus not found How can I store that error message inside a string? Any help would be greatly appreciated. Thanks! bash scripting string share|improve this question asked May 29 '14 at 7:25 Miguel Roque 1172412 I tried running this command: var=$(/sbin/modprobe -n -v hfsplush) And then displaying it: $var But it still doesn't capture the error message inside the string. –Miguel Roque May 29 '14 at 7:42 add a comment| 4 Answers 4 active oldest votes up vote 10 down vote you can do it by redirecting errors command: /sbin/modprobe -n -v hfsplus 2> fileName as a script #!/bin/bash errormessage=$( /sbin/modprobe -n -v hfsplus 2> &1) echo $errormessage or #!/bin/bash errormessage=`/sbin/modprobe -n -v hfsplus 2> &1 ` echo $errormessage if you want to append the error use >> instead of > share|improve this answer edited May 29 '14 at 7:48 answered May 29 '14 at 7:42 Networker 4,69962756 I've tried that approach and it stores it DIRECTLY in the text file. I want it to store inside a string first so I can format the contents easily. –Miguel Roque May 29 '14 at 7:45 1 @MiguelRoque see updates –Networker May 29 '14 at 7:46 1 I tried putting the output inside a HEREDOC and it work
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like you, helping each other. Join them; it only takes a minute: Sign up Bash how do you capture stderr to a variable? [duplicate] up vote 15 down vote favorite 5 This question already has an answer http://unix.stackexchange.com/questions/132511/how-to-capture-error-message-from-executed-command here: Bash script - store stderr in variable [duplicate] 4 answers Bash how do you capture stderr to a variable? I would like to do something like this inside of my bash script sh -c path/myExcecutable-bin 2>&1 =MYVARIABLE How do you send stderror output to a variable ? bash stderr share|improve this question edited Jun 18 '12 at 16:57 Tim Pote 13.4k23344 asked Jun 18 '12 at 16:55 stackoverflow 4,0212380143 marked as duplicate by tripleeebash http://stackoverflow.com/questions/11087499/bash-how-do-you-capture-stderr-to-a-variable Users with the bash badge can single-handedly close bash questions as duplicates and reopen them as needed. Mar 14 at 6:56 This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question. 2 This StackOverflow thread should answer your question. –Web User Jun 18 '12 at 16:57 See one of the many related threads, and several solutions –ormaaj Jun 18 '12 at 17:01 add a comment| 1 Answer 1 active oldest votes up vote 33 down vote accepted To save both stdin and stderr to a variable: MYVARIABLE="$(path/myExcecutable-bin 2>&1)" To save just stderr to a variable: MYVARIABLE="$(path/myExcecutable-bin 2>&1 > /dev/null)" share|improve this answer edited Jun 18 '12 at 17:06 answered Jun 18 '12 at 16:56 Tim Pote 13.4k23344 4 I just want to note that you will save both stderr and stdout to the variable. When you need only stderr use 2>&1 >/dev/null –Igor Chubin Jun 18 '12 at 16:59 @IgorChubin Good point. I was basing my original answer on what it looked like the OP wanted to do, but that isn't necessarily what they actually wanted. See my changes. –Tim Pote Jun 18 '12 at 17:08 add a comment| Not the answer you're looking for? Browse other questions tagged bash stderr
and Signals and Traps (Oh My!) - Part 1 by William Shotts, Jr. In this lesson, we're going to look at handling errors during the execution of your scripts. The difference between a good program and a poor one http://linuxcommand.org/wss0150.php is often measured in terms of the program's robustness. That is, the program's ability to handle situations in which something goes wrong. Exit status As you recall from previous lessons, every well-written program returns an http://www.cyberciti.biz/faq/linux-redirect-error-output-to-file/ exit status when it finishes. If a program finishes successfully, the exit status will be zero. If the exit status is anything other than zero, then the program failed in some way. It is very error message important to check the exit status of programs you call in your scripts. It is also important that your scripts return a meaningful exit status when they finish. I once had a Unix system administrator who wrote a script for a production system containing the following 2 lines of code: # Example of a really bad idea cd $some_directory rm * Why is this such a bad way of doing it? capture error message It's not, if nothing goes wrong. The two lines change the working directory to the name contained in $some_directory and delete the files in that directory. That's the intended behavior. But what happens if the directory named in $some_directory doesn't exist? In that case, the cd command will fail and the script executes the rm command on the current working directory. Not the intended behavior! By the way, my hapless system administrator's script suffered this very failure and it destroyed a large portion of an important production system. Don't let this happen to you! The problem with the script was that it did not check the exit status of the cd command before proceeding with the rm command. Checking the exit status There are several ways you can get and respond to the exit status of a program. First, you can examine the contents of the $? environment variable. $? will contain the exit status of the last command executed. You can see this work with the following: [me] $ true; echo $? 0 [me] $ false; echo $? 1 The true and false commands are programs that do nothing except return an exit status of zero and one, respectively. Using them, we can see how the $? environment variable c
am a new Ubuntu Linux and bash shell user. I also know how to redirect output from display/screen to a file using the following syntax:
cmd > file ls > fileHowever, some time errors are displayed on screen. How do I store and redirect output from the computer screen to a file on a Linux or Unix-like systems? Bash / ksh and other modern shell on Linux has three file descriptors:stdin (0)stdout (1)stderr (2)Syntax To redirect all output to fileThe syntax is as follows to redirect output (stdout) as follows:command-name > output.txt command-name > stdout.txtSyntax To redirect all error to fileThe syntax is as follows to redirect errors (stderr) as follows:command-name 2> errors.txt command-name 2> stderr.txtSyntax to redirect both output (stdout) and errors (stderr) to different filesThe syntax:command1 > out.txt 2> err.txt command2 -f -z -y > out.txt 2> err.txtSyntax to redirect both output (stdout) and errors (stderr) to same fileThe syntax is:command1 > everything.txt 2>&1 command1 -arg > everything.txt 2>&1Syntax to redirect errors (stderr) to null or zero devicesData written to a null or zero special file is discarded by your system. This is useful to silence out errors (also know as ‘error spam'):command1 2> /dev/null command1 2> /dev/zero command2 -arg 2> /dev/null command2 -arg 2> /dev/zeroTip: Use tee command to redirect to both a file and the screen same timeThe syntax is:command1 |& tee log.txt ## or ## command1 -arg |& tee log.txt ## or ## command1 2>&1 | tee log.txtAnother usage:#!/bin/bash # My script to do blah ... foo(){ : } 2>&1 | tee foo.logOR#!/bin/bash # My script to do blah ... { command1 command2 } 2>&1 | tee script.log Share this tutorial on:TwitterFacebookGoogle+Download PDF version Found an error/typo on this page?About the author: Vivek Gite is a seasoned sysadmin and a trainer for the Linux/Unix & shell scripting. Follow him on Twitter. OR read more like this:BASH Shell Redirect Output and Errors To /dev/nullBASH Shell: How To Redirect stderr To stdout ( redirect stderr to a File )Unix and Linux: Redirect Error Output To null CommandHow do I save or redirect stdout and stderr into different files?Linux / Unix Find Command: Avoid Permission Denied Me