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Bash Command Error Handling


You need to make sure that both the old and the new directories are moved to locations that are on the same partition so you can take advantage of the property bash shell terminal share|improve this question asked Feb 25 '14 at 9:09 Lee Probert 2,35152335 Why not an if else ? –Thomas Ayoub Feb 25 '14 at 9:11 The problem with the script was that it did not check the exit status of the cd command before proceeding with the rm command. I shudder remembering a monster Ultrix installation script written with just these conditional constructions I once tried to decipher... –vonbrand Dec 27 '15 at 22:15 add a comment| up vote 31 http://waspsoft.com/error-handling/bash-script-command-error-handling.html

I like the try/catch so much. –erm3nda Jul 24 '15 at 17:51 @erm3nda Glad to hear that! 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 But it's okay to mention that here. –Alfe Feb 26 '14 at 10:49 add a comment| Your Answer draft saved draft discarded Sign up or log in Sign up using What type of sequences are escape sequences starting with "\033]" How to deal with a very weak student?

Bash Error Handling Best Practices

Why can a Gnome grapple a Goliath? function directoryExists { cd $1 if [ $? = 0 ] then echo -e "${green}$1${NC}" else echo -e "${red}$1${NC}" fi } # EXE directoryExists "~/foobar" directoryExists "/www/html/drupal" The script works, but trap "error_exit 'Received signal SIGHUP'" SIGHUP trap "error_exit 'Received signal SIGINT'" SIGINT trap "error_exit 'Received signal SIGTERM'" SIGTERM #Alias the function so that it will print a message with the following The solution to this is to make the changes an (almost) atomic operation.

You might write: for file in $(find /var/www -type f -name "*.html"); do perl -pi -e 's/www.example.net/www.example.com/' $file done Now if there is a problem with the script you could have It is your best friend. If those conditions are true, then check whether or not it has a size greater than 0. #!/bin/bash echo "Which error log are you checking today? " read answer if [ Bash Throw Error It also fails to check whether the user has permission to cd into it. –Ian D.

command ; then ... ; fi. [ is itself a command, and it's not needed in this case. –Keith Thompson Jan 13 '12 at 10:19 8 @Joe: My way also Linux is a registered trademark of Linus Torvalds. set +e command1 command2 set -e On a slightly related note, by default bash takes the error status of the last item in a pipeline, which may not be what you Subtraction with a negative result Is this safe to display MySQL query error in webpage if something went wrong?

A simple visual puzzle to die for How could banks with multiple branches work in a world without quick communication? Bash Catch Errors The fix is to use: if [ ! -e $lockfile ]; then trap "rm -f $lockfile; exit" INT TERM EXIT touch $lockfile critical-section rm $lockfile trap - INT TERM EXIT else I'd be worried that some unexpected behavior might result. share|improve this answer answered Aug 28 '14 at 17:43 Dan Fabulich 10.7k2479112 add a comment| up vote 2 down vote And you have traps http://www.tldp.org/LDP/Bash-Beginners-Guide/html/sect_12_02.html which is not the same, but

Error Handling In Bash Shell Script

Thanks for editing. –JRFerguson Oct 22 '13 at 13:36 add a comment| up vote 0 down vote Actually for your case I would say that the logic can be improved. If you would like this to fail, then you can use set -o pipefail to make it fail. Bash Error Handling Best Practices ls | bogus_command # bash: bogus_command: command not found echo $? # 0 # Note that the ! Powershell Command Error Handling Join them; it only takes a minute: Sign up Here's how it works: Anybody can ask a question Anybody can answer The best answers are voted up and rise to the

share|improve this answer edited Aug 29 '14 at 19:21 answered Oct 9 '08 at 4:06 Charles Duffy 94.5k15102142 3 @draemon the variable capitalization is intentional. weblink I usually just copy-and-paste the code below into my scripts. Bash doesn't have as many luxuries as one can find in many programming languages. Allen 53228 That also fixes (unless xpg_echo is on) the issues when filenames contain backslash characters. –Stéphane Chazelas Oct 22 '13 at 14:28 add a comment| up vote 4 Dos Command Error Handling

Are there any 'smart' ejection seats? Least Common Multiple I do not get any ether when mining Is the standard Canon 18-55 lens the same as 5 years ago? tempfiles=( ) cleanup() { rm -f "${tempfiles[@]}" } trap cleanup 0 error() { local parent_lineno="$1" local message="$2" local code="${3:-1}" if [[ -n "$message" ]] ; then echo "Error on or near navigate here Now I have all the information I want to log.

You're running ping in a subshell of a subshell, the output of ping is captured in view of running it as a command. Error Handling In Linux if "`command` returns any error"; then echo "Returned an error" else echo "Proceed..." fi bash control-flow share|improve this question edited Oct 16 '11 at 23:57 Michael Mrozek♦ 44.9k19144179 asked Oct 16 Within a script, an exit nnn command may be used to deliver an nnn exit status to the shell (nnn must

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You can read more about parameter expansion in the bash man page under the topic "EXPANSIONS". command ] doesn't execute command; it treats command as a string and treats it as true because it has a non-zero length. [ is a synonym for the test command –Keith Using -e gives you error checking for free. Bash Error Code Also, note the inclusion of the LINENO environment variable which will help you identify the exact line within your script where the error occurred. #!/bin/bash # A slicker error handling routine

You can check for files with files open by using lsof. The wait builtin will return the exit code of the inner command, and now you're using || after wait, not the inner function, so set -e works properly inside the latter: By the way, my hapless system administrator's script suffered this very failure and it destroyed a large portion of an important production system. his comment is here Intuition behind Harmonic Analysis in Analytic Number Theory American English: are [ə] and [ʌ] different phonemes?

See also stackoverflow.com/questions/673055/… –Charles Duffy Jun 9 '11 at 3:25 before you break it again, test your change. Force Microsoft Word to NEVER auto-capitalize the name of my company What are the canonical white spaces? there are dark corners in the Bourne shell, and people use all of them.

--Chet Ramey

The exit command terminates a script, share|improve this answer answered Sep 17 '13 at 6:36 German Rumm 21123 3 If you want to do something if it fails, and preserve the exit code (to show in


The equivalent of a bare exit is exit $? or even just omitting the exit.

#!/bin/bash COMMAND_1 . . . share|improve this answer edited Dec 16 '13 at 9:55 community wiki 7 revsLuca Borrione 2 this thing is awesome.. That's the intended behavior. Previous | Contents | Top | Next © 2000-2016, William E.

Race conditions It's worth pointing out that there is a slight race condition in the above lock example between the time we test for the lockfile and the time we create If you need more information to pass along with your simulated exception, you can use the stdout of the subshells, but that is a bit complicated and maybe another question ;-)