Lua: Help with capturing part of a string with magic patterns

[Thonex]

Hey guys,

I'm unable to figure out a way using magic characters in LUA to ignore everything between the second and last underscore.

Example... I have this:

Inst_1A_8ch_Sus_Leg_idx001_sn_056_en_055

And I want the result to be:

Inst_1A_055

I was hoping to use some sort of form of string.sub(filename, filename:match(".*()/")+1)) type of code to do it for me. Anyone know what the proper pattern would be?

Thanks.

[Meo-Ada Mespotine]

You can use string.match with multiple captures, like in this example, where the parts of the string of the first (.-_.-_) and the second (.*) are stored in B and C respectively:

A="Inst_1A_8ch_Sus_Leg_idx001_sn_056_en_055"

B,C=A:match("(.-_.-_).*_(.*)")
D=B..C

The first capture (.-_.-_) says:
Take everything from beginning to the first _ and then between the first _ to the second _

inbetween the captures, it shall ignore everthing until the last _

the last capture (.*) says
take everything fom after the last _ til the end.

[Thonex]

Originally Posted by Meo-Ada Mespotine

You can use string.match with multiple captures, like in this example, where the parts of the string of the first (.-_.-_) and the second (.*) are stored in B and C respectively:

A="Inst_1A_8ch_Sus_Leg_idx001_sn_056_en_055"

B,C=A:match("(.-_.-_).*_(.*)")
D=B..C

The first capture (.-_.-_) says:
Take everything from beginning to the first _ and then between the first _ to the second _

inbetween the captures, it shall ignore everthing until the last _

the last capture (.*) says
take everything fom after the last _ til the end.

Brilliant!!!

Thanks so much Mespotine!!! I really will try to digest this... as I'm needing manipulate strings more and more.

Maybe I should learn Klingon to help 😀

Thanks again!!

[Meo-Ada Mespotine]

The most important things are

.- and .* as well as captures () and the knowledge, that magic characters in your string can prevent proper pattern-matching, so they need to be escape with a % before them.

for instance

%.%* will look for the characters .* in a string while .* will look for the whole string and returning the whole string because of that.

If you get that, then most of pattern matching can be done.

The rest is sugar for specific usecases.


Just toy around with simple patterns and try to make the matching work. If you got a sense for them, you can work your way up from there.

[Thonex]

Originally Posted by Meo-Ada Mespotine

The most important things are

.- and .* as well as captures () and the knowledge, that magic characters in your string can prevent proper pattern-matching, so they need to be escape with a % before them.

for instance

%.%* will look for the characters .* in a string while .* will look for the whole string and returning the whole string because of that.

If you get that, then most of pattern matching can be done.

The rest is sugar for specific usecases.


Just toy around with simple patterns and try to make the matching work. If you got a sense for them, you can work your way up from there.

Thanks for the very clear and detailed explanation!!

That actually helps me a lot!

Cheers,

Andrew K