CLI grep in ESA is compatible with which REGEX?

[ehealthsupport]

I use this REGEX ^DOC[1-9]\d{0,}\.[p][d][f] to match "DOC54321.pdf" or "DOC4321.pdf" or "DOC321.pdf" or "DOC21.pdf" or "DOC1.pdf" and it pass the online python REGEX test. (https://regex101.com/)

But this seems not working in CLI grep? Where I can find the ESA grep REGEX cheat sheet?

Thanks!

[Robert Sherwin]

See the following:

https://www.cisco.com/c/en/us/support/docs/security/email-security-appliance/117968-troubleshoot-grep-00.html

https://www.cisco.com/c/en/us/support/docs/security/web-security-appliance/117938-configure-wsa-00.html