Check Error Code In Unix
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The exit command terminates a script, just as in a C program. It can also return a value, which is available to the script's parent process.Every command returns an exit 32512 error code unix status (sometimes referred to as a return status or exit code).255 Error Code In Unix
A successful command returns a 0, while an unsuccessful one returns a non-zero value that usually can be interpreted as 256 error code unix an error code. Well-behaved UNIX commands, programs, and utilities return a 0 exit code upon successful completion, though there are some exceptions.
Likewise, functions within a script and the script itself return an exitUnix Error Code 16
status. The last command executed in the function or script determines the exit status. Within a script, an exit nnn command may be used to deliver an nnn exit status to the shell (nnn must be an integer in the 0 - 255 range).
When a script ends with an exit that has no parameter, the exit status of the script is the exit unix error code 137 status of the last command executed in the script (previous to the exit).#!/bin/bash COMMAND_1 . . . COMMAND_LAST # Will exit with status of last command. exitThe equivalent of a bare exit is exit $? or even just omitting the exit.#!/bin/bash COMMAND_1 . . . COMMAND_LAST # Will exit with status of last command. exit $?#!/bin/bash COMMAND1 . . . COMMAND_LAST # Will exit with status of last command.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
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on a lot of automation and monitoring projects, a big part of these projects are taking
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existing scripts and modifying them to be useful for automation and monitoring tools. One thing I have noticed is sometimes scripts use exit unix error code 2 codes 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? http://tldp.org/LDP/abs/html/exit-status.html On 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. http://bencane.com/2014/09/02/understanding-exit-codes-and-how-to-use-them-in-bash-scripts/ Any script 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 simpl
1, 2008 in AIX, BASH Shell, CentOS, Debian / Ubuntu, FreeBSD, Linux, Openbsd, Programming, RedHat and Friends, Solaris-Unix, Ubuntu Linux, UNIXQ. Can you explain the exit status of shell and commands under http://www.cyberciti.biz/faq/shell-how-to-determine-the-exit-status-of-linux-and-unix-command/ Linux / UNIX operating system? A. All UNIX and Linux command has a http://askubuntu.com/questions/29370/how-to-check-if-a-command-succeeded several parameters or variables that can be use to find out the exit status of command. Please note that these parameters or variables may only be referenced assignment to them is not allowed. You can use $? to find out the exit status of command. $? always expands to the status of error code the most recently executed foreground command or pipeline. For example, you run the command cal: $ cal Now to see exit status of cal command type following command: $ echo $? Output:
0Zero means command executed successfully, if exit status returns non-zero value then your command failed to execute. For example run command called cyberciti $ cyberciti Output:bash: cyberciti: command not foundDisplay exit status of the unix error code command: $ echo $? Output:127Value 127 (non-zero) indicates command cyberciti failed to execute. You can use exit status in shell scripting too. You can store result of exit status in variable. Consider following shell script:#!/bin/bash echo -n "Enter user name : " read USR cut -d: -f1 /etc/passwd | grep "$USR" > /dev/null OUT=$? if [ $OUT -eq 0 ];then echo "User account found!" else echo "User account does not exists in /etc/passwd file!" fiSave and execute the script as follows: $ chmod +x script.sh$ ./script.sh Output:Enter user name : jradmin User account does not exists in /etc/passwd fileTry it one more time: $ ./script.sh Output:Enter user name : vivek User account foundAs you can see, I have used grep command to find out user name stored in USR variable. If grep command finds user name in /etc/passwd command output it would return exit status of zero. This is stored in OUT variable. Next, if command makes decision based upon exit status stored in OUT variable. 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/U
communities company blog Stack Exchange Inbox Reputation and Badges sign up log in tour help Tour Start here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site About Us Learn more about Stack Overflow the company Business Learn more about hiring developers or posting ads with us Ask Ubuntu Questions Tags Users Badges Unanswered Ask Question _ Ask Ubuntu is a question and answer site for Ubuntu users and developers. 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 top How to check if a command succeeded? up vote 62 down vote favorite 21 Is there any way to check if there is an error in executing a command? Example : test1=`sed -i "/:@/c connection.url=jdbc:oracle:thin:@$ip:1521:$dataBase" $search` valid $test1 function valid () { if $test -eq 1; then echo "OK" else echo "ERROR" fi } I already tried do that but it seems it isn't working. I don't how do that. command-line share|improve this question edited Mar 7 '11 at 13:41 Octavian Damiean 10.1k54160 asked Mar 7 '11 at 11:40 moata_u 71861523 5 Prefer $(foo) over backticks `foo`, because you can nest it, and it's easier to distinguish from apostrophes. –user unknown Mar 26 '11 at 18:19 add a comment| 5 Answers 5 active oldest votes up vote 97 down vote accepted The return value is stored in $?. 0 indicates success, others indicates error. some_command if [ $? -eq 0 ]; then echo OK else echo FAIL fi Like any other textual value, you can store it in a variable for future comparison: some_command retval=$? do_something $retval if [ $retval -ne 0 ]; then echo "Return code was not zero but $retval" fi For possible comparison operators, see man test. share|improve this answer edited Mar 7 '11 at 13:14 answered Mar 7 '11 at 12:06 Lekensteyn 85.6k34220292 That's nice ...can i hold the output error ??!! , because in this case i have 2 error : command error "text" ex, file not found and my error "text" Which is in this case failed for example –moata_u Mar 7 '11 at 12:28 @moata_u: you can s