Bash Stop Execution If Error
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Bash Exit On Error With Message
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Shell Script Error Handling
you, helping each other. Join them; it only takes a minute: Sign up Stop on first error [duplicate] up vote 115 down vote favorite 28 Possible Duplicate: Automatic exit from bash shell script on error How can I have bash stop on the first command failure, without putting stuff like this all through my code? some_prog || bash errexit exit 1 some_other_prog || exit 1 bash share|improve this question asked Aug 13 '10 at 6:45 Matt Joiner 41.2k43213382 marked as duplicate by martin clayton, Barmar, Toto, codesparkle, Emil Vikström Oct 13 '12 at 10:31 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. add a comment| 1 Answer 1 active oldest votes up vote 237 down vote accepted Maybe you want set -e: http://www.davidpashley.com/articles/writing-robust-shell-scripts.html#id2382181 share|improve this answer answered Aug 13 '10 at 6:50 Alok Singhal 48.8k1290125 31 Be aware of set -e gotchas: mywiki.wooledge.org/BashFAQ/105 –Kris Jun 9 '15 at 10:57 1 @Kris thanks for the link, very interesting. –Alok Singhal Jun 10 '15 at 3:45 2 @Kris, you just broke my heart. I thought -e was infallible. –Trenton Sep 30 '15 at 3:17 add a comment| Not the answer you're looking for? Browse other questions tagged bash or ask your own question. asked 6 years ago viewed
Bash Prompts About Writing Robust Bash Shell Scripts Many people hack together shell scripts quickly to do simple tasks, but these soon take on a life of their own. Unfortunately shell scripts are full of
Bash Script Exit On Error
subtle effects which result in scripts failing in unusual ways. It's possible bash disable exit on error to write scripts which minimise these problems. In this article, I explain several techniques for writing robust bash scripts. Use bash set +e set -u How often have you written a script that broke because a variable wasn't set? I know I have, many times. chroot=$1 ... rm -rf $chroot/usr/share/doc If you ran the script http://stackoverflow.com/questions/3474526/stop-on-first-error above and accidentally forgot to give a parameter, you would have just deleted all of your system documentation rather than making a smaller chroot. So what can you do about it? Fortunately bash provides you with set -u, which will exit your script if you try to use an uninitialised variable. You can also use the slightly more readable set -o nounset. david% bash /tmp/shrink-chroot.sh $chroot= david% http://www.davidpashley.com/articles/writing-robust-shell-scripts/ bash -u /tmp/shrink-chroot.sh /tmp/shrink-chroot.sh: line 3: $1: unbound variable david% Use set -e Every script you write should include set -e at the top. This tells bash that it should exit the script if any statement returns a non-true return value. The benefit of using -e is that it prevents errors snowballing into serious issues when they could have been caught earlier. Again, for readability you may want to use set -o errexit. Using -e gives you error checking for free. If you forget to check something, bash will do it or you. Unfortunately it means you can't check $? as bash will never get to the checking code if it isn't zero. There are other constructs you could use: command if [ "$?"-ne 0]; then echo "command failed"; exit 1; fi could be replaced with command || { echo "command failed"; exit 1; } or if ! command; then echo "command failed"; exit 1; fi What if you have a command that returns non-zero or you are not interested in its return value? You can use command || true, or if you have a longer section of code, you can turn off the error che
here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings http://unix.stackexchange.com/questions/82224/how-to-make-bash-abort-the-execution-of-a-script-on-syntax-error and policies of this site About Us Learn more about Stack Overflow the http://linuxcommand.org/wss0150.php company Business Learn more about hiring developers or posting ads with us Unix & Linux Questions Tags Users Badges Unanswered Ask Question _ Unix & Linux Stack Exchange is a question and answer site for users of Linux, FreeBSD and other Un*x-like operating systems. Join them; it only takes if error 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 top How to make bash abort the execution of a script on syntax error? up vote 14 down vote favorite 5 To be on safe side, I'd like bash abort the execution of a script if it exit on error encounters a syntax error. To my surprise, I can't achieve this. (set -e is not enough.) Example: #!/bin/bash # Do exit on any error: set -e readonly a=(1 2) # A syntax error is here: if (( "${a[#]}" == 2 )); then echo ok else echo not ok fi echo status $? echo 'Bad: has not aborted execution on syntax error!' Result (bash-3.2.39 or bash-3.2.51): $ ./sh-on-syntax-err ./sh-on-syntax-err: line 10: #: syntax error: operand expected (error token is "#") status 1 Bad: has not aborted execution on syntax error! $ Well, we can't check $? after every statement to catch syntax errors. (I expected such safe behavior from a sensible programming language... perhaps this must be reported as a bug/wish to bash developers) More experiments if makes no difference. Removing if: #!/bin/bash set -e # exit on any error readonly a=(1 2) # A syntax error is here: (( "${a[#]}" == 2 )) echo status $? echo 'Bad: has not aborted execution on syntax error!' Result: $ ./sh-on-syntax-err ./sh-on-syntax-err: line 6: #: syntax error: operand expected (error token is "#") status 1 Bad: has no
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 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 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 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? 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 contains the exit status of the previous program. So to check the exit status, we could write the script this way: # Check the exit status cd $some_directory if [ "$?" = "0" ]; then rm * else echo "Cannot change directory!" 1>&2 exit 1 fi In this version, we examine the exit status of the c