Dos Shell Script Error Handling
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Error Handling In Unix Shell Script
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Dos Shell Script Tutorial
Batch Files - Error Handling up vote 34 down vote favorite 2 I'm currently writing my first batch file for deploying an asp.net solution. I've been Googling a bit for a general error handling approach and can't find anything really useful. Basically if any thing goes wrong I want to stop and print out what went wrong. Can anyone give me any pointers? dos batch file error handling batch-file share|improve this question edited Apr 29 '14 at 11:28 John Saunders 138k20175321 asked Jul 22 '09 at 9:15 bplus 2,87494574 add a comment| 5 Answers 5 active oldest votes up vote 34 down vote I generally find the conditional command concatenation operators much more convenient than ERRORLEVEL. yourCommand && ( echo yourCommand was successful ) || ( echo yourCommand failed ) There is one complication you should be aware of. The error branch will fire if the last command in the success branch raises an error. yourCommand && ( someCommandThatMayFail ) || ( echo This will fire if yourCommand or someCommandThatMayFail raises an error ) The fix is to insert a harmless command that is guaranteed to succeed at the end of the success branch. I like to use (call ), which does nothing except set the ERRORLEVEL to 0. There is a corollary (call) that does nothing except set the ERRORLEVEL to 1. yourCommand && ( someCommandThatMayFail (call ) ) || ( echo This can only fire if yourCommand raises an error ) See Foolproof way to check for nonzero (error) return code in wind
stdin, stdout, stderr Part 5 – If/Then Conditionals Part 6 – Loops Part 7 – Functions Part 8 – Parsing Input Part 9 – Logging
Linux Script Error Handling
Part 10 – Advanced Tricks Today we’ll cover return codes as the right dos shell programming way to communicate the outcome of your script’s execution to the world. Sadly, even skilled Windows programmers overlook the importance return error code from batch file of return codes. Return Code Conventions By convention, command line execution should return zero when execution succeeds and non-zero when execution fails. Warning messages typically don’t effect the return code. What matters http://stackoverflow.com/questions/1164049/batch-files-error-handling is did the script work or not? Checking Return Codes In Your Script Commands The environmental variable %ERRORLEVEL% contains the return code of the last executed program or script. A very helpful feature is the built-in DOS commands like ECHO, IF, and SET will preserve the existing value of %ERRORLEVEL%. The conventional technique to check for a non-zero return code using the NEQ (Not-Equal-To) operator of http://steve-jansen.github.io/guides/windows-batch-scripting/part-3-return-codes.html the IF command: IF %ERRORLEVEL% NEQ 0 ( REM do something here to address the error ) Another common technique is: IF ERRORLEVEL 1 ( REM do something here to address the error ) The ERRORLEVEL 1 statement is true when the return code is any number equal to or greater than 1. However, I don’t use this technique because programs can return negative numbers as well as positive numbers. Most programs rarely document every possible return code, so I’d rather explicity check for non-zero with the NEQ 0 style than assuming return codes will be 1 or greater on error. You may also want to check for specific error codes. For example, you can test that an executable program or script is in your PATH by simply calling the program and checking for return code 9009. SomeFile.exe IF %ERRORLEVEL% EQU 9009 ( ECHO error - SomeFile.exe not found in your PATH ) It’s hard to know this stuff upfront – I generally just use trial and error to figure out the best way to check the return code of the program or script I’m calling. Remember, this is duct tape programming. It
Checking and Running as Scheduled Tasks ★★★★★★★★★★★★★★★ Paul Adams (ex-MSFT)June 6, 201016 0 0 0 Batch files may be considered “old hat” by a lot of people (or a complete mystery to the https://blogs.technet.microsoft.com/mrsnrub/2010/06/06/batch-files-basic-error-checking-and-running-as-scheduled-tasks/ younger ones!) but they are sometimes still the easiest way to execute simple jobs http://armillz.blogspot.com/2011/10/common-dos-batch-file-error-handling.html as they have practically no requirements other than a command shell process to run within – yes there is a strong probability that a script could achieve an identical (or at least equivalent) result, but the fact is that it will be more complex and therefore longer to create and administer. Something that trips up a error handling fair number of people is the difference between double-clicking a .BAT file and scheduling it as a task to run at a certain time, on a trigger or on a schedule – it can seem that the batch file just simply does not run at all, and the return code sent back to the Task Scheduler is often 0x2, “path not found”, even though the file most definitely is there. script error handling When you double-click a .BAT or .CMD file through Explorer, a cmd.exe process is started to provide the environment in which it will run. The credentials used are your own (or more correctly, inherited from the Explorer process). The “current working directory” is set to that where the batch file lives. When the Task Scheduler service starts the same batch file it actually invokes an instance of cmd.exe (as SYSTEM impersonating the user whose credentials are defined in the task) to carry out the process and waits for it to exit with a return code – the current working directory for this process is not that of the batch file, but that of cmd.exe itself. i.e. %windir%\system32 Now, if your batch file assumes that you launched it through Explorer or from an existing command prompt with the current working directory set to its own location, you can run into problems. One simple way to verify if your batch file should work as a scheduled task is to call it from an existing cmd.exe process from a different current working directory (such as your profile, or a temp folder). Be very, very careful if your batch file does any kind of file deletion – especially if wildcards are invol
don't make any sense. I'm sure they made perfect sense to me at the time. ;-) Wednesday, October 5, 2011 Common DOS batch file error handling mistakes I make I write a decent amount of batch scripts now days to automate things on windows server boxes. Unfortunately, I don't do it quite frequently enough to remember all the crazy syntax of DOS commands. One of these errors is error handling. These are the things I commonly need to deal with. I found this page (and site) very helpful for all DOS related stuff: http://www.robvanderwoude.com/errorlevel.php Use "IF %ERRORLEVEL% NEQ 0 SET MYERROR=1" to record whether the previous command resulted in an error code. Alternately, you can check for "IF ERRORLEVEL 1 ..." if you want to look for a specific error level. Be cautious of manipulations with ERRORLEVEL. It's not really an environment variable like other variables. In particular, do NOT ever use "set ERRORLEVEL=5" or similar. It will corrupt any further use of %ERRORLEVEL% syntax by fixing it at a value. Use "CALL FOO.BAT" instead of just "FOO.BAT" when calling subscripts. Otherwise, when that script completes it will not return to the current script. Use "EXIT /B 1" to return an exit code from your script. If you use "EXIT 1" it will exit the entire command shell, including closing your current window if it's running in one. Consider using SETLOCAL and ENDLOCAL within your script to prevent temporary environment variables from carrying through to outer shells. Below is an example script. :: Sample script with some error handling SETLOCAL SET MYPARAM=%1 if "%MYPARAM%"=="" goto :USAGE CALL .\childscript.bat %MYPARAM% if %ERRORLEVEL% NEQ 0 set MYERROR=1 echo. echo Finished child script. Handling errors now... if %MYERROR%==1 GOTO :ERROR echo It worked! ENDLOCAL set SOME_EXTERNAL_VARIABLE=1 GOTO :EOF :USAGE echo Please provide a command line parameter. EXIT /B 2 :ERROR echo It didn't work, dude. EXIT /B 1 Update: I was wrong about the ERRORLEVEL syntax earlier, so I updated after some testing. Posted by Richard Mills at 10:01 AM Labels: DOS, windows No comments: Post a Comment Newer Post Older Post Home Subscribe to: Post Comments (Atom) Followers Blog Archive ► 2013 (1) ► November (1) ► 2012 (9) ► November (1) ► October (2) ► September (1) ► July (1) ► June (3) ► January (1) ▼ 2011 (17) ► December (1) ► November (1) ▼ October (4) Repairing 'svnsync: malformed file' error with sub... DOS batch file stderr redirection Common DOS batch file error handling mistakes I ma... Change