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Certain REGEX strings in transforms.conf will fail

Splunk Employee
Splunk Employee

I have requierement where i need to route data from certain sources to a specific index. The index name will be extracted from a specific location in the path when it's only preceded by a certain other segment. Example (this is a windows box - notice the path separators):

[send_to_index]
REGEX = bar\\[[:alnum::]]\\
DEST_KEY = queue
FORMAT = indexQueue

In this case I need to extract the path segment that comes after bar and send that path's data to the index with extract's name. The setup is simple and should work but it doesn't.

1 Solution

Splunk Employee
Splunk Employee

After some careful exploration I have an answer that might benefit the community. The short answer is "do not end your REGEX in backslash".
A btool --debug for the above gives the following:

splunk cmd btool --debug transforms list send_to_index
system [send_to_index]
system CAN_OPTIMIZE = True
system CLEAN_KEYS = True
system DEFAULT_VALUE =
system DEST_KEY =
system FORMAT = indexQueue
system KEEP_EMPTY_VALS = False
system LOOKAHEAD = 4096
system MV_ADD = False
system REGEX = bar\\[[:alnum:]]\
DEST_KEY = queue
system SOURCE_KEY = _raw
system WRITE_META = False

You clearly can see that DEST_KEY is not considered by the system and consequently the setup fails. The culprit behind this appears to be that last backslash.
It turns out that in .conf files the presence of a backslash at the end of a line will escape the implied newline there.

Easy Fix - do NOT end the REGEX with backslash:

[send_to_index]
REGEX = bar\\[[:alnum::]]\\\w+
DEST_KEY = queue
FORMAT = indexQueue

OR, if you need a backslash there, escape it and bracket it.

[send_to_index]
REGEX = bar\\[[:alnum::]][\\]
DEST_KEY = queue
FORMAT = indexQueue

Hope this helps.

View solution in original post

Splunk Employee
Splunk Employee

After some careful exploration I have an answer that might benefit the community. The short answer is "do not end your REGEX in backslash".
A btool --debug for the above gives the following:

splunk cmd btool --debug transforms list send_to_index
system [send_to_index]
system CAN_OPTIMIZE = True
system CLEAN_KEYS = True
system DEFAULT_VALUE =
system DEST_KEY =
system FORMAT = indexQueue
system KEEP_EMPTY_VALS = False
system LOOKAHEAD = 4096
system MV_ADD = False
system REGEX = bar\\[[:alnum:]]\
DEST_KEY = queue
system SOURCE_KEY = _raw
system WRITE_META = False

You clearly can see that DEST_KEY is not considered by the system and consequently the setup fails. The culprit behind this appears to be that last backslash.
It turns out that in .conf files the presence of a backslash at the end of a line will escape the implied newline there.

Easy Fix - do NOT end the REGEX with backslash:

[send_to_index]
REGEX = bar\\[[:alnum::]]\\\w+
DEST_KEY = queue
FORMAT = indexQueue

OR, if you need a backslash there, escape it and bracket it.

[send_to_index]
REGEX = bar\\[[:alnum::]][\\]
DEST_KEY = queue
FORMAT = indexQueue

Hope this helps.

View solution in original post