===== OnError (Statement) =====

==== Format ====
**onerror** [[labelprogramsyntax|label]]

==== Description ====
Causes the [[GosubReturn|Gosub]] at [[labelprogramsyntax|label]] to be executed when a runtime error occurs.  Program control may be resumed at the next statement with a [[GosubReturn|Return]] statement in the subroutine.  Error traps are kept in a stack so that the last defined trap, that has not been removed with an [[offerror|OffError]] will be the active one.

You may not execute an OnError statement inside a [[Try|Try / Catch / End Try]] statement.

==== Example ====

<code>
# test error trapping
onerror nicetrap
print 1
next haha
print 2
open 999, "bogus.file"
print "Runs Anyway"

# test error trapping off and fail at any error (default)
offerror
print 3
next hoho
print "never get here"

end

nicetrap:
# this is the nice error handler
print "trap and run - error on line " + lasterrorline + " - error number " + lasterror + " message " + lasterrormessage + " (" + lasterrorextra + ")"
return
</code>
will display\\
<code>
1
trap and run - error on line 4 - error number 4 message Next without FOR ()
2
trap and run - error on line 6 - error number 5 message Invalid File Number ()
Runs Anyway
3
ERROR on line 12: Next without FOR 
</code>

See additional example of usage on [[ThrowError|ThrowError]] page.

==== See Also ====
{{page>en:start#Error Handling&noheader}}

==== History ==== 
|0.9.6z|New To Version|
|1.99.99.33|Removed the ability to use a subroutine for error trapping|