Csh Error Handling
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Shell Script Error Handling
to know if a shell error occurred . source /scripts/scriptThatWillFail.csh linux shell csh share|improve this question asked Jul 3 '15 at 19:54 Leo 7711224 add a comment| 1 Answer 1 active oldest votes up vote 1 down vote accepted The exit/return code is stored in the status variable in C shell. source /scripts/scriptThatWillFail.csh if ($status != 0) then echo failed else echo passed endif share|improve this answer edited Jul 9 '15 at 22:32 answered Jul 3 '15 at 20:01 Eugeniu Rosca 4,027528 add a comment| bash script ignore error continue Your Answer draft saved draft discarded Sign up or log in Sign up using Google Sign up using Facebook Sign up using Email and Password Post as a guest Name Email Post as a guest Name Email discard By posting your answer, you agree to the privacy policy and terms of service. Not the answer you're looking for? Browse other questions tagged linux shell csh or ask your own question. asked 1 year ago viewed 217 times active 1 year ago Related 219Can a shell script set environment variables of the calling shell?580How to set a variable equal to the output from a command in Bash?0What does the -b argument do in csh?3csh inline math2How to run a csh script from a sh script0csh shell script troubleshooting0How to show line number when executing csh script?1Shell Script (Csh shell) send attachement0How to define 'alias' in csh1Csh echo foreach loop index Hot Network Questions Is "The empty set is a subset of any set" a convention? Is there a proof of infinitely many primes p such that p-2 and p+2 are composite numbers? How do I debug an emoticon-based URL? How can I get Name of all apex class having api version less than 36 in my org? Bash scripting - how to concatenate the following strings? When Sudoku met Ratio Is there a single word for people who inhabit rural areas? Tips for work-life balance when doing postdoc with two very young children and a one hour commute My math students conside
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 bash trap error measured in terms of the program's robustness. That is, the program's ability to handle
Shell Script Exit Code
situations in which something goes wrong. Exit status As you recall from previous lessons, every well-written program returns an exit status when
Try Catch In Shell Script
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 http://stackoverflow.com/questions/31213467/how-to-catch-errors-or-exceptions-in-csh 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 http://linuxcommand.org/wss0150.php 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 s
HCL Search Reviews Search ISOs Go to Page... LinuxQuestions.org > Forums > Non-*NIX Forums > Programming Error handling in csh/tcsh User Name Remember Me? Password Programming This forum is for all programming questions. The question does not http://www.linuxquestions.org/questions/programming-9/error-handling-in-csh-tcsh-814821/ have to be directly related to Linux and any language is fair game. Notices Welcome https://www.dssw.co.uk/blog/2012-10-08-how-to-add-error-checking-to-your-shell-scripts/ to LinuxQuestions.org, a friendly and active Linux Community. You are currently viewing LQ as a guest. By joining our community you will have the ability to post topics, receive our newsletter, use the advanced search, subscribe to threads and access many other special features. Registration is quick, simple and absolutely free. Join our community today! Note that registered members see error handling fewer ads, and ContentLink is completely disabled once you log in. Are you new to LinuxQuestions.org? Visit the following links: Site Howto | Site FAQ | Sitemap | Register Now If you have any problems with the registration process or your account login, please contact us. If you need to reset your password, click here. Having a problem logging in? Please visit this page to clear all LQ-related cookies. Introduction to Linux - A Hands csh error handling on Guide This guide was created as an overview of the Linux Operating System, geared toward new users as an exploration tour and getting started guide, with exercises at the end of each chapter. For more advanced trainees it can be a desktop reference, and a collection of the base knowledge needed to proceed with system and network administration. This book contains many real life examples derived from the author's experience as a Linux system and network administrator, trainer and consultant. They hope these examples will help you to get a better understanding of the Linux system and that you feel encouraged to try out things on your own. Click Here to receive this Complete Guide absolutely free. Search this Thread 06-17-2010, 06:22 PM #1 lucmove Member Registered: Aug 2005 Location: Brazil Distribution: Debian Jessie Posts: 711 Rep: Error handling in csh/tcsh I want to check the hostname of my box. Maybe there are better ways to do it, but here is my attempt. Even if I eventually do it some other way, I still think I need to learn how to cope with the errors: Code: if ( -x `which hostname` ) then setenv HOSTNAME `hostname` else if ( -e /etc/HOSTNAME ) then setenv HOSTNAME `cat /etc/HOSTNAME` else if ( -e /etc/hostname ) then setenv HOSTNAME `cat /etc/hostname` endif T
article shows how to add error checking to highlight problems you might otherwise miss. Access the shell on Mac via the Terminal.app Unlike more recently designed languages, shell script does not have an easy answer for error handling. There are no common exception handling routines or ways of wrapping up large blocks of script and asking for errors to fall through to a provided subroutine. Instead shell script asks you, the author, to check individual program exit codes and branch as needed in case of an error. In practice, this means your once short script is going to get a little longer and a little more involved. Unix Exit Status Each program you run through a shell script returns an exit status. This numeric status value tells the calling script if the program completed successfully or if an error was encountered. The exit status is not visible on the command line. This makes it difficult to tell if something went wrong just by looking at the textual output of a shell script. It is possible - even common - for scripts to print nothing and yet encounter multiple errors. Let's consider this simple script: #!/bin/sh cp /Volumes/Documents/criticalfile.txt /Volumes/BackUp/. This script does one thing; it copies a single file from one volume to another using the cp program. Thankfully the cp program is chatty and will print a message if an error is encountered. That is great for us reviewing the output visually, but for the shell running our script the error will go completely unnoticed. This is a problem if our script goes on to do more work, or if we want the script to robustly deal with errors. Let's add error checking to this simple script. #!/bin/sh cp /Volumes/Documents/criticalfile.txt /Volumes/BackUp/. if [ "$?" != "0" ]; then echo "[Error] copy failed!" 1>&2 exit 1 fi We have added an if/fi block below the cp line. The new block checks the special variable $? to see if it equals 0 or not. Unix programs should return 0 if they completed successfully. Any other value means something went wrong. The exact meaning of the returned value is frequently documented in the program's man page. If an error is detected in our script's if/fi block, then a message is printed and the script immediately exits also reporting an error. Why report another error? If our script does not explicitly say exit 1 then the script is assumed to have completed successfully. The error from