Stuck on /^^

[sublee]

^^ is a weird regexp. When I grep it with the /^^ command, tig got stuck.

These regexps make tig get stuck:

• ^^
• $$
• (a|a?)+
• (a?|a+)*

[cascassette]

Is that because those are illegal or stupid expressions? Can't have $$ nor ^^, third and fourth are both equal to a*.

[sublee]

Yes, they are stupid or malicious but not illegal.

^^ means that a literal ^ at the head in BRE (only the first ^ is treated as a metacharacter), or just any heads in ERE and/or PCRE (same with single ^). (a|a?)+ is a malicious expression obviously. It is usually used for ReDoS attacks. It can be optimized as a* as you mentioned. But it is also not an illegal regexp.

grep doesn't get stuck with those regexps.