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How To Check Return Code In Unix Script

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By the way, my hapless system administrator's script suffered this very failure and it destroyed a large portion of an important production system. Follow him on Twitter. PROGNAME=$(basename $0) function error_exit { # ---------------------------------------------------------------- # Function for exit due to fatal program error # Accepts 1 argument: # string containing descriptive error message # ---------------------------------------------------------------- echo "${PROGNAME}: ${1:-"Unknown I know I have, many times. his comment is here

For more details see the following link. true\" = $?" # 1 # Note that the "!" needs a space between it and the command. # !true leads to a "command not found" error # # The '!' You can get this # value from the first item on the command line ($0). Privacy - Terms of Service - Questions or Comments The exit status of a command From Linux Shell Scripting Tutorial - A Beginner's handbook Jump to: navigation, search ← Multilevel if-then-elseHomeConditional http://linuxcommand.org/wss0150.php

Bash Script Exit On Error

Home Resources Polls Contact Me / Advertising Search This Blog Monday, March 24, 2008 How to check the exit status code When a command finishes execution, it returns an exit code. Previous | Contents | Top | Next © 2000-2017, William E. trap command signal [signal ...] There are many signals you can trap (you can get a list of them by running kill -l), but for cleaning up after problems there are only

  1. It's possible to write scripts which minimise these problems.
  2. cmd1 exit code is in $pipestatus[1], cmd3 exit code in $pipestatus[3], so that $?
  3. You usually want something like if ls -al file.ext; then : nothing; else exit $?; fi which of course like @MarcH says is equivalent to ls -al file.ext || exit $?
  4. An advantage is that you now have a backup before you made your changes in case you need to revert. © 2013 Company Name UNIX & Linux

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 Improving the error exit function There are a number of improvements that we can make to the error_exit function. I am running Ubuntu Dapper Drake Linux.Keep it coming, it is good stuff.Rob Reply Link Rob April 3, 2007, 6:59 pmG'day again,Nope, I was wrong the script works I didn't copy Last Exit Code Destiny Instead of just giving you information like some man page, I hope to illustrate each command in real-life scenarios.

share|improve this answer edited Jun 13 '15 at 17:05 eadmaster 367414 answered Jun 13 '15 at 14:34 llua 3,752817 1 Valid for this particular example, but only usable if there Bash Set Exit Code How Do I Store Exit Status Of The Command In a Shell Variable? no matchgrep foo /tmp/bar.txt || echo "text not found"# grep returns 0, e.g. http://stackoverflow.com/questions/90418/exit-shell-script-based-on-process-exit-code You can surround a variable name with curly braces (as with ${PROGNAME}) if you need to be sure it is separated from surrounding text.

in the check_exit_status argument list. Exit Code 0 For grep, 0 means that the string was found, and 1 (or higher), otherwise. I like to include the name of the program in the error message to make clear where the error is coming from. 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

Bash Set Exit Code

more hot questions question feed lang-sh about us tour help blog chat data legal privacy policy work here advertising info mobile contact us feedback Technology Life / Arts Culture / Recreation Fortunately bash provides you with set -u, which will exit your script if you try to use an uninitialised variable. Bash Script Exit On Error All UNIX and Linux command has a several parameters or variables that can be use to find out the exit status of command. Exit Bash Shell share|improve this answer edited Mar 17 '12 at 19:37 gatoatigrado 7,684445102 answered Jan 29 '09 at 22:07 Vladimir Graschenko add a comment| up vote 16 down vote for bash: # this

But ssh worked. http://1pxcare.com/exit-code/unix-command-line-return-code.html An AND list has the form command1 && command2 command2 is executed if, and only if, command1 returns an exit status of zero. Thanks for sharing, and thanks for the above comment. No more, no less. - As thoroughly debated with you and explained there, all three suggestions in the other answer are well defined by POSIX. Bash Neq

if [ $OUT -eq 0 ];then echo "User account found!" else echo "User account does not exists in /etc/passwd file!" fi#!/bin/bash echo -n "Enter user name : " read USR cut if [ $filename = "foo" ]; will fail if $filename contains a space. For example run command called cyberciti $ cyberciti Output:bash: cyberciti: command not foundDisplay exit status of the command: $ echo $? weblink How are water vapors not visible?

Using if, we could write it this way: # A better way if cd $some_directory; then rm * else echo "Could not change directory! Shell Script Return Value cp -a /var/www /var/www-tmp for file in $(find /var/www-tmp -type f -name "*.html"); do perl -pi -e 's/www.example.net/www.example.com/' $file done mv /var/www /var/www-old mv /var/www-tmp /var/www This means that if there Why would two species of predator with the same prey cooperate?

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.

Here is the bash manual section on the set builtin. You successfully submitted the job, so you get a zero exit code. You then need to use -0 with xargs. Bash Exit On Error Reply Link saravanakumar June 12, 2011, 2:44 pmVery useful…thanks a lot…its makes me to understand about "$?".

First, you can examine the contents of the $? It would be nice if you could fix these problems, either by deleting the lock files or by rolling back to a known good state when your script suffers a problem. Assign $? check over here You can save the exit status using a variable: command -p sudo ...

share|improve this answer answered Sep 18 '08 at 6:09 Allen 4,0101428 21 What does it do? And so anyway, if that is what you're trying to do: command -pv sudo >/dev/null || handle_it command -p sudo something or another ...would work just fine as a test without I use this construct in scripts where i want to provide alternatives for the same command. The solution to this is to make the changes an (almost) atomic operation.

Reply Link Security: Are you a robot or human?Please enable JavaScript to submit this form.Cancel replyLeave a Comment Name * Email * Comment You can use these HTML tags and attributes: For a more portable solution you can do: command -p sudo ... is updated after each command exits. Nor was portability mentioned anywhere in the question, thus i gave a answer that works in said shell.

Note the inclusion # of the LINENO environment variable. You can also just avoid the RETVAL altogether and use the "||" or "&&" operands which are called when the command on the left returns 1 or 0 respectively, e.g.# grep should return the sudo exit status, but instead it always returns 0 (the exit code of the test). cmd1 exit code is in ${PIPESTATUS[0]}, cmd3 exit code in ${PIPESTATUS[2]}, so that $?

exit / exit status

#!/bin/bash echo hello echo $? # Exit status 0 returned because command executed successfully.