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?

Answer 1

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.)

Answer 2

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=

Answer 3

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

Answer 4

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]*$

Answer 5

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.