Linux Command Line Error Code
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Shell Script Exit Code
Unix & Linux Questions Tags Users Badges Unanswered Ask Question _ Unix & Linux Stack Exchange is bash if exit code a question and answer site for users of Linux, FreeBSD and other Un*x-like operating systems. Join them; it only takes a minute: Sign up Here's how linux exit code it works: Anybody can ask a question Anybody can answer The best answers are voted up and rise to the top How can I get the error code (exit code) of “xdg-mime query filetype” command? up vote 0 down vote favorite I ran xdg-mime
Bash Script Exit On Error
query filetype
Exit Code 0
372k696761127 asked Mar 22 '11 at 2:53 Amanda 3401414 Now I set XDG_UTILS_DEBUG_LEVEL=100, the out put is: Runing file -i "file name" and then the mime type is "application/octet-stream" (unknown file type) but no error code is given. –Amanda Mar 22 '11 at 2:55 add a comment| 2 Answers 2 active oldest votes up vote 4 down vote accepted In Bourne-derived shells (sh, ash, bash, dash, zsh...) the exit code of the last-run program is in the $? variable: $ ls /no-such-file ls: /no-such-file: No such file or directory $ echo $? 2 So in this case, the exit code of ls is 2. share|improve this answer answered Mar 22 '11 at 3:43 Warren Young 41.2k4105129 Thank you both! It's not an error here and the error code is 0. –Amanda Mar 22 '11 at 8:49 add a comment| up vote 0 down vote "application/octet-stream" (unknown file type) is not an error message, it simply means that file does not know what your file contains. This could happen for encrypted files for example, they look so random that file is unable to print something more precise than "this is data". share|improve this answer answered Mar 22 '11 at 5:53 Frederik Deweerdt 2,589712 add a comment| Your Answer draft saved draft discarded Sign up or log in Sign up using Google Sign up using Facebook Sign up using Email and Password Post as a guest Name Email Post as a guest Name Email discard By posting your answer, you agree to the privacy policy
Resources Polls Contact Me / Advertising Search This Blog Monday, March 24, 2008 How to check the exit status code When a command finishes execution, it returns an exit code. The exit code is not displayed on the screen by default. To examine the exit code, exit bash shell you need to examine a special variable, "$?" Say, you are searching for a string in a
Bash Exit On Error
text file. $ grep x1y2z3 somefile.txt $ The standard output of the command returns null, which is a pretty good indication that the string cannot bash if exit code not 0 be found in the file. But what if you embed the grep command in a script? How can you tell if the string is found or not? Checking the exit code will tell you. Let's first try it out interactively. $ grep http://unix.stackexchange.com/questions/9857/how-can-i-get-the-error-code-exit-code-of-xdg-mime-query-filetype-command x1y2z3 somefile.txt $ echo $? 1 Note that in bash, the exit status is 0 if the command succeeded, and 1 if failed. For grep, 0 means that the string was found, and 1 (or higher), otherwise. To check the exit status in a script, you may use the following pattern: somecommand argument1 argument2 RETVAL=$? [ $RETVAL -eq 0 ] && echo Success [ $RETVAL -ne 0 ] && echo Failure Posted by Peter Leung at 7:50 PM Email ThisBlogThis!Share to TwitterShare to FacebookShare to http://linuxcommando.blogspot.com/2008/03/how-to-check-exit-status-code.html Pinterest 4 comments: Mad MAx said... $RETVAL=$?is not correct.when you assign a value to a variable, in bash, you can't prepend variable name with $.The correct form isRETVAL=$?regards, Mad Max. August 4, 2009 at 3:07 AM Peter Leung said... Thanks, Mad MAx.I made the correction.Peter August 4, 2009 at 8:50 PM Anonymous said... 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 returns 1, e.g. no matchgrep foo /tmp/bar.txt || echo "text not found"# grep returns 0, e.g. matchgrep baz /tmp/bar.txt && echo "found it!" April 25, 2011 at 2:56 PM Wang said... Thanks for sharing, and thanks for the above comment. July 31, 2012 at 11:59 AM Post a Comment Newer Post Older Post Home Subscribe to: Post Comments (Atom) Followers Subscribe in a reader Enter your email address:Delivered by FeedBurner Follow @commandolinux Popular Posts How to disable SSH host key checking How to Display Routing Table How to connect to a WPA/WPA2 WiFi network using Linux command line Using sed to extract lines in a text file How to get the process start date and time Blog Archive ► 2016 (2) ► July (1) ► January (1) ► 2015 (20) ► November (1) ► October (1) ► July (2) ► June (2) ► May (2) ► April (5) ► March (2) ► February (4) ► January (1) ► 2014 (50) ► December (2) ► November (2) ►
exit codes, exit codes are important and this article describes how to use them in your scripts and understand them in general. Written by Benjamin Cane on 2014-09-02 14:45:00| 4 min read Sponsored by Lately I've been working on http://bencane.com/2014/09/02/understanding-exit-codes-and-how-to-use-them-in-bash-scripts/ a lot of automation and monitoring projects, a big part of these projects are taking existing scripts and modifying them to be useful for automation and monitoring tools. One thing I have noticed is sometimes scripts use exit codes http://www.ibm.com/support/knowledgecenter/SSEPGG_9.7.0/com.ibm.db2.luw.admin.cmd.doc/doc/r0010411.html and sometimes they don't. It seems like exit codes are easy for poeple to forget, but they are an incredibly important part of any script. Especially if that script is used for the command line. What are exit codes? On exit code Unix and Linux systems, programs can pass a value to their parent process while terminating. This value is referred to as an exit code or exit status. On POSIX systems the standard convention is for the program to pass 0 for successful executions and 1 or higher for failed executions. Why is this important? If you look at exit codes in the context of scripts written to be used for the command line the answer is very simple. Any script bash if exit that is useful in some fashion will inevitably be either used in another script, or wrapped with a bash one liner. This becomes especially true if the script is used with automation tools like SaltStack or monitoring tools like Nagios, these programs will execute scripts and check the status code to determine whether that script was successful or not. On top of those reasons, exit codes exist within your scripts even if you don't define them. By not defining proper exit codes you could be falsely reporting successful executions which can cause issues depending on what the script does. What happens if I don't specify an exit code In Linux any script run from the command line has an exit code. With Bash scripts, if the exit code is not specified in the script itself the exit code used will be the exit code of the last command run. To help explain exit codes a little better we are going to use a quick sample script. Sample Script: #!/bin/bash touch /root/test echo created file The above sample script will execute both the touch command and the echo command. When we execute this script (as a non-root user) the touch command will fail, ideally since the touch command failed we would want the exit code of the script to indicate failure with an appropriate exit code. To check the exit code we can simply print the $? sp