Regular expressions in findstr

Question

I'm doing a little string validation with findstr and its /r flag to allow for regular expressions. In particular I'd like to validate integers.

The regex

^[0-9][0-9]*$

worked fine for non-negative numbers but since I now support negative numbers as well I tried

^([1-9][0-9]*|0|-[1-9][0-9]*)$

for either positive or negative integers or zero.

The regex works fine theoretically. I tested it in PowerShell and it matches what I want. However, with

findstr /r /c:"^([1-9][0-9]*|0|-[1-9][0-9]*)$"

it doesn't.

While I know that findstr doesn't have the most advanced regex support (even below Notepad++ which is probably quite an achievement), I would have expected such simple expressions to work.

Any ideas what I'm doing wrong here?

Note to the editor: The *windows* tag is a little superfluous, given that `findstr` only exists there ... — Joey, Apr 10 '10 at 15:41
Rössel: Tags are there to help find things. A moderate redundancy doesn't hurt in this case. — jfs, Apr 10 '10 at 20:18
I'd never search for a tag as overcrowded as *windows* ;-) but if you think it'll help ... — Joey, Apr 10 '10 at 22:44
and don't forget the tag usage to filter out questions. Those overcrowded tags as *windows*, *linux*, *apple*, are **very** convenient to *ignore* — PA., Mar 15 '11 at 13:21

score 62 · Accepted Answer · answered Apr 11 '10 at 00:29

62

This works for me:

findstr /r "^[1-9][0-9]*$ ^-[1-9][0-9]*$ ^0$"

If you don't use the /c option, the <Strings> argument is treated as a space-separated list of search strings, which makes the space a sort of crude replacement for the | construct. (As long as your regexes don't contain spaces, that is.)

answered Apr 11 '10 at 00:29

Alan Moore

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Aah, right you are. That one I forgot. Yes, spaces in the RE would be bad, then but that won't be an issue here. – Joey Apr 11 '10 at 08:53
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I'm reluctant to up-vote such an abuse of regular expression syntax, but you solved my problem, thank-you! :-p – yoyo Dec 12 '12 at 02:32

Joey · Answer 2 · 2010-04-10T16:32:58.620

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Argh, I should have read the documentation better. findstr apparently doesn't support alternations (|).

So I'm probably back to multiple invocations or replacing the whole thing with a custom parser eventually.

This is what I do for now:

set ERROR=1
rem Test for zero
echo %1|findstr /r /c:"^0$">nul 2>&1
if not errorlevel 1 set ERROR=
rem Test for positive numbers
echo %1|findstr /r /c:"^[1-9][0-9]*$">nul 2>&1
if not errorlevel 1 set ERROR=
rem Test for negative numbers
echo %1|findstr /r /c:"^-[1-9][0-9]*$">nul 2>&1
if not errorlevel 1 set ERROR=

edited Apr 10 '10 at 16:32

answered Apr 10 '10 at 15:13

Joey

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As suggested by Alan Moore, if your search string does not contain spaces, then the space character will work like | in 'regular' regular expressions :) if all you're doing is looking to output any line that contains a list of strings you have. – smartexpert Jul 27 '17 at 15:37
@smartexpert: You may have noticed that Alan's answer is the accepted one. – Joey Jul 27 '17 at 15:54

score 3 · Answer 3 · answered Apr 10 '10 at 15:19

3

Or if you can, download grep for windows.. Many more features than findstr provides.

answered Apr 10 '10 at 15:19

ghostdog74

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No option here. This is a pure batch bignum library. I'll go for a proper parser when I'm done with the basic arithmetic. This will also be much better for proper error messages. For now multiple `findstr` invocations should suffice. Also, if it were just for features I'd just call PowerShell. Much easier, much more powerful. – Joey Apr 10 '10 at 15:22
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I'm fascinated to I know went anyone would want bignums in a bat file. – Denis Howe Mar 10 '18 at 10:54

score 1 · Answer 4 · edited Apr 08 '16 at 11:23

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A simpler regex that achieves the same thing is possible, just add an optional minus to the start of your original expression:

^-?[0-9][0-9]*$

edited Apr 08 '16 at 11:23

Mihriban Minaz

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answered Apr 08 '16 at 10:40

martski

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This is incorrect: it will match negative zero, and integers with a leading zero, either positive or negative: `-0`, `01`, `-042` etc. while OP's regex does not. Also, `findstr` does not support the `?` quantifier, so this answer really is not relevant to OP's issue – joH1 Feb 10 '23 at 17:31

score 0 · Answer 5 · answered Jun 13 '19 at 13:14

0

Support for regex in findstr is quite limited. I suggest using Notepad++. The find in files option supports Perl Compatible Regular Expressions; results showing filename, line number and matching text can be easily copied to a text file.

answered Jun 13 '19 at 13:14

Paulo Merson

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Notepad++ is not really a useful option for non-interactive scripting. – Joey Jun 13 '19 at 13:31

Regular expressions in findstr

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