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;doc:csv: Regular expressions in CSV rules

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Simon Michael 2025-11-19 10:05:55 -10:00
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@ -4002,7 +4002,7 @@ Eg `! whole foods`, `! %3 whole foods`, `!%description whole foods` will match i
The pattern is, as usual in hledger, a POSIX extended regular expression
that also supports GNU word boundaries (`\b`, `\B`, `\<`, `\>`) and nothing else.
If you have trouble with it, see "Regular expressions" in the hledger manual (<https://hledger.org/hledger.html#regular-expressions>).
For more details and tips, see [Regular expressions in CSV rules](#regular-expressions-in-csv-rules) below.
### Multiple matchers
@ -4273,6 +4273,34 @@ data. See:
- <https://hledger.org/cookbook.html#setups-and-workflows>
- <https://plaintextaccounting.org> -> data import/conversion
### Regular expressions in CSV rules
Regular expressions in `if` conditions (AKA matchers) are as described at <https://hledger.org/hledger.html#regular-expressions> -
a POSIX extended regular expression, that also supports GNU word boundaries (`\b`, `\B`, `\<`, `\>`), and nothing else.
Here are some examples that might be useful in CSV rules:
- Is field "foo" truly empty ? `if %foo ^$`
- Is it empty or containing only whitespace ? `if %foo ^ *$`
- Is it non-empty ? `if %foo .`
- Does it contain non-whitespace ? `if %foo [^ ]`
Testing the value of numeric fields is a little harder.
You can't use hledger queries like `amt:0` or `amt:>10` in CSV rules.
But you can often achieve the same thing with a regular expression.
Also, remember the content and layout of number fields in CSV can vary a lot.
And can change if you switch data providers in future.
So it's a good idea to write defensive, robust regexps for numeric fields.
Here are some examples; you may need to adapt them to your data:
- Does foo contain a non-zero number ? `if %foo [1-9]`
- Is it negative ? `if %foo -`
- Is it non-negative ? `if ! %foo -`
- Is it >= 10 ? `if %foo [1-9][0-9]+\.|` (assuming a decimal period and no leading zeroes)
- Is it >=10 and < 20 ? `if %foo \b1[0-9]\.|`
### Setting amounts
Continuing from [amount field](#amount-field) above, here are more tips for amount-setting: